The photochemical dimerization of norbornadiene using chromium carbonyls
by Brian Kellog Hill
A thesis submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree of
DOCTOR OF PHILOSOPHY in Chemistry
Montana State University
© Copyright by Brian Kellog Hill (1969)
Abstract:
Norbornadiene has previously been shown to undergo dimerization photochemically with Group VI
and VIII and thermally with Group VIII unsubstituted metal carbonyls. Furthermore,
diene-iron-tricarbonyls cause the reaction to be more stereospecific and give only two products instead
of the usual eleven obtained using the unsubstituted metal carbonyls. To learn if this change in products
was generally characteristic of unsubstituted and substituted metal carbonyls a series of chromium
carbonyls were investigated. The products of the chromium metal carbonyls were three trans dimers, a
saturated cage dimer and one ketone insertion product. A possible mechanism for the photochemical
dimerization of norbornadiene using chromium hexacarbonyl and substituted chromium carbonyl as
sensitizers was determined. A common intermediate for the reactions has been proposed. THE PHOTOCHEMICAL DIMERIZATION OF NORBORNADIENE
USIN G CHROM IUM CARBONYLS'
by
BRIAN KELLOGG HILL
A t h e s i s s u b m itte d to th e G ra d u a te F a c u lty in p a r tia l
fu lf illm e n t o f th e re q u ire m e n ts fo r th e d e g re e
of
DOCTOR OF PHILOSOPHY
in
,
C h e m istry
A pproved:
H e a d , M a jo r D e p a rtm e n t
CHairmanT Exaumhing C o m m ittee
MONTANA STATE UNIVERSITY
B o z e m a n ,' M o n ta n a
A u g u st, 1969
ill
ACKNOWLEDGEMENT
The a u th o r w o u ld lik e to a c k n o w le d g e D r..E . W . J e n n in g s for h is
e n c o u ra g e m e n t a n d a d v i c e , w ith o u t w h ic h th is r e s e a r c h w o u ld n o t h a v e
b e e n c o m p le te d .
S p e c ia l r e c o g n itio n i s d u e th e a u th o r 's w if e , G a y le , fo r h e r c o n fi­
d en ce and s a c rific e s .
A p p re c ia tio n is e x p r e s s e d to th e N a tio n a l D e fe n s e E d u c a tio n Act
fo r th e f in a n c ia l a s s i s t a n c e o f a f e llo w s h ip .
iv
TABLE OF CONTENTS
P ag e
LIST OF TABLES
.....................................i . ■....................................... .........................
vi
LIST OF FIGURES
..........................................................................................................
v ii
ABSTRACT . . . . .
................................................................................' ........................
x
IN T R O D U C T IO N .............................................................................................................
I
D IS C U S S IO N ................................................................................................ '..................
25
P ro c e d u re fo r D e te rm in in g P ro d u c ts a n d P ro d u ct
R a tio s .......................................................................................................................
27
I s o la tio n o f In te rm e d ia te s U sin g C hrom ium
H e x a c a r b o n y l............. ■......................................... ■................................................
34
I s o la tio n o f In te rm e d ia te s fo r B e n z e n e , T o lu en e o r
M e s ity le n e C hrom ium T r ic a r b o n y l...............................................................
41
O th e r I n v e s t i g a t i o n s .........................................................................................
56
CONCLUSION
.................................................................................................................
60
EXPERIMENTAL..............................................' .....................' ........................................
70
R e a g e n t s ....................................................................................................................
70
I n s t r u m e n t s ...........................................................
71
L ig h t a n d R e a c tio n S y ste m s ............................................................................
72
P h o to r e a c tio n fo r D e te rm in in g P ro d u c ts an d P ro d u ct
R a tio s ............................................................................................................. ... . .
73
I s o la tio n o f P h o to re a c tio n In te rm e d ia te s
.............................. ... . . . .
81
P h o to c h e m ic a l Time S t u d y ...............................................................................
85
B e e r's L a w ................................................................................
86
In fra re d S t u d y .......................................................................................................
86
T h erm al R e a c tio n o f C hrom ium H e x a c a rb o n y l a n d
N o r b o r n a d i e n e ....................................................
86
I r r a d ia tio n o f N o rb o rn a d ie n e W ith o u t M e ta l C a r b o n y l ...........................87
P h o to r e a c tio n o f N o r b o r n e n e .....................................................
87
V
P ag e
EXPERIMENTAL (c o n tin u e d )
T herm al R e a c tio n o f P y rid in e C hrom ium P e n ta c a rb o n y l
a n d N o rb o rn a d ie n e .........................................................................................
87
T herm al R e a c tio n o f D ip y rid in e C hrom ium
T e tra c a rb o n y l a n d N o rb o rn a d ie n e
........................................................
88
I s o la tio n o f C a rb o n y l P o l y m e r ..................................................................
89,
LITERATURE CITED
90
vi
LIST OF TABLES
P ag e
I.
T r a n s itio n C o m p le x e s W ith N o r b o r n a d i e n e ........................................
14
II.
D im e r s , T rim ers a n d K eto n es o f N o r b o r n a d i e n e ..............................
15
M e ta l C a rb o n y l R e a c ta n t T e m p la te s
. . . ...........................................
25
IV.
E x p e rim e n ta l P ro c e d u re fo r P ro d u c t I d e n t i f i c a t i o n ...........................
28
V.
P ro d u c t R a tio s o f N o rb o rn a d ie n e D i m e r s ...............................................
32
VI.
P e a k A s s ig n m e n ts for th e M a s s S p ectru m o f th e Red
C o m p le x .................................................................................................................
50
III.
v ii
LIST OF FIGURES
P ag e
1.
P ic to r ia l R e p r e s e n ta tio n o f th e Bond B etw een
P la tin u m a n d E t h y l e n e ..................................................... .......................... .
4
2.
P ic to r ia l R e p r e s e n ta tio n o f a M e ta l C arb o n y l B o n d .......................
7
3.
S tru c tu re o f a B ridged a n d T rip le B ridged C a r b o n y l ........................
8
4.
N o n - c o n c e r te d M e c h a n ism fo r th e F o rm atio n o f
N o rb o rn a d ie n e D i m e r s ...............................................
23
N u c le a r M a g n e tic R e s o n a n c e S p e c tra o f
N o rb o rn a d ie n e D i m e r s ...................................................................................
29
N u c le a r M a g n e tic R e s o n a n c e S p e c tru m o f
N o rb o rn a d ie n e C ag e D i m e r .........................................................................
30
In fra re d S p ectru m o f C hrom ium H e x a c a rb o n y l
S o lu tio n a t Zero. Time o f I r r a d i a t i o n ................................. ...
36
In fra re d S p e c tru m o f C hrom ium H e x a c a rb o n y l
S o lu tio n a f te r Two H ours o f I r r a d ia tio n . .............................. ... . . .
36
In fra re d S p e c tru m o f C hrom ium H e x a c a rb o n y l
S o lu tio n a f te r S ix H ours o f I r r a d i a t i o n ....................................................
37
In fra re d S p ectru m o f C hrom ium H e x a c a rb o n y l
S o lu tio n a f te r Two H ours o f I r r a d ia tio n an d Six
H o u rs in th e D a r k ................................................................................' . . . . ■
39
In fra re d S p ectru m o f M e s ity le n e C hrom ium
T ric a rb o n y l S o lu tio n a t Zero Tim e o f I r r a d i a t i o n ..............................
43
In fra re d S p ectru m o f M e s ity le n e C hrom ium
T ric a rb o n y l S o lu tio n a f te r 30 M in u te s o f Ir ra d ia tio n
....................
43
.......................
44
In fra re d S p e c tru m o f M e s ity le n e C hrom ium
T ric a rb o n y l S o lu tio n a f te r 3^/2 H o u rs o f I r r a d i a t i o n .......................
44
In fra re d S p ectru m o f M e s ity le n e C hrom ium
T ric a rb o n y l S o lu tio n a f te r 30 M in u te s o f Ir ra d ia tio n
a n d S ix H ours in th e D a r k .............................. .............................................
45
5.
6.
7.
8.
9.
10.
IT .
12.
13.
14.
1 5.
In fra re d S p e c tru m o f M e s ity le n e C hrom ium
T ric a rb o n y l S o lu tio n a f te r O ne H o u r o f Ir ra d ia tio n
v iii
Page
16.
M a s s S p ectru m o f N o rb o rn a d ie n e C hrom ium
T e tr a c a r b o n y l...................................................................................... '...............
47
1 7.
In fra re d S p ectru m o f Red C o m p le x ...........................................................
48
1 8.
M a s s S p ectru m o f Red C o m p l e x ........................................... ...................
49
19.
In fra re d S p ectru m o f B en zen e C hrom ium T ric a rb o n y l
a t Zero Time o f I r r a d i a t i o n .........................................................................
52
In fra re d S p e c tru m o f B en z e n e C hrom ium T ric a rb o n y l
a f te r 30 M in u te s o f I r r a d i a t i o n .................................................................
52
In fra re d S p ectru m o f B en zen e C hrom ium T ric a rb o n y l
a f te r O ne H our o f I r r a d i a t i o n .....................................................................
53
In fra re d S p e c tru m o f B en zen e C hrom ium T ric a rb o n y l
a f te r 31/2 H ours o f Ir r a d ia tio n ..................................................................
53 .
In fra re d S p ectru m o f T o lu en e C hrom ium T ric a rb o n y l
a t Zero Time o f I r r a d i a t i o n .........................................................................
54
In fra re d S p ectru m o f T o lu en e C hrom ium T ric a rb o n y l
a f te r 30 M in u te s o f I r r a d i a t i o n ...................................................................
54
In fra re d S p ectru m o f T o lu en e C hrom ium T ric a rb o n y l
a f te r O ne H our o f I r r a d i a t i o n ......................................................................
55
In fra re d S p ectru m o f T o lu en e C hrom ium T ric a b o n y l
a f te r 3Yz H ours o f Ir r a d ia tio n ..................................................................
55
P lo t o f P e a k H e ig h t o f G as C h ro m a to g ra p h an d
I n te n s ity o f In fra re d B ands v e r s u s T im e ,
C hrom ium H e x a c a r b o n y l ...............................................................................
- 58
P lo t o f P e a k P Ieight o f G as C h ro m a to g ra p h an d
I n te n s ity o f In fra re d B ands v e r s u s T im e ,
M e s ity le n e C hrom ium T r ic a r b o n y l.............................................. ... . . .
58
20.
21.
22.
23.
24.
25.
26.
27.
28.
2 9 . . P o s s ib le W ay s fo r C hrom ium to Bond to
N o rb o rn a d ie n e . .................................................................................................
30.
F o rm atio n o f N o rb o rn a d ie n e C hrom ium T e tra c a rb o n y l
from C hrom ium H e x a c a r b o n y l".................... .................................................
60
63
•V
ix
P ag e
31.
32.
33.
F o rm atio n o f N o rb o rn a d ie n e C hrom ium T e tra c a rb o n y l
from A rene C hrom ium T r i c a r b o n y l ............. "............................................
65
F o rm atio n o f D im ers U sin g D in o rb o rn a d ie n e
C hrom ium T e t r a c a r b o n y l ...............................................................................
67
F o rm atio n o f C a g e D im er u s in g D in o rb o rn a d ie n e
C hrom ium T r i c a r b o n y l ................................. ................................................
68
X
ABSTRACT
N o rb o m a d ie n e h a s p r e v io u s ly b e e n sh o w n to u n d e rg o d im e riz a tio n
p h o to c h e m ic a lly w ith G roup VI a n d VIII a n d 'th e r m a lly w ith G roup VIII
u n s u b s tit u te d m e ta l c a rb o n y ls . F u rth e rm o re , d ie n e - ir o n - tr ic a r b o n y ls
c a u s e th e r e a c tio n to be m ore s t e r e o s p e c if ic an d g iv e o n ly tw o p ro d u c ts
in s t e a d o f th e u s u a l e le v e n o b ta in e d u s in g th e u n s u b s titu te d m e ta l
c a r b o n y ls . To le a r n i f th is c h a n g e in p ro d u c ts w a s g e n e r a lly c h a r a c te r ­
i s t i c o f u n s u b s titu te d a n d s u b s tit u te d m e ta l c a rb o n y ls a s e r ie s o f
chrom ium c a rb o n y ls w e re in v e s t i g a t e d . The p ro d u c ts o f th e chrom ium
m e ta l c a rb o n y ls w e re th r e e tr a n s d im e r s , a s a tu r a te d c a g e d im e r an d o n e
k e to n e in s e r tio n p ro d u c t. A p o s s ib le m e c h a n is m for th e p h o to c h e m ic a l
d im e riz a tio n o f n o rb o rn a d ie n e u s in g chrom ium h e x a c a rb o n y l an d s u b s t i ­
tu te d chrom ium c a rb o n y l a s s e n s i t i z e r s w a s d e te rm in e d . A com m on i n t e r ­
m e d ia te fo r th e r e a c tio n s h a s b e e n p ro p o s e d .
INTRODUCTION
An in v e s tig a tio n o f th e p e rio d ic ta b le w ill re v e a l th a t 86 o f th e 104
c h a r a c te r iz e d e le m e n ts h a v e an e le c tr o n e g a tiv ity o f l e s s th a n 2.2 (I) a n d
t h a t t h e s e 86 e le m e n ts c o m p ris e e ith e r th e m e ta l o r th e m e ta llo id e l e ­
m e n ts . S in c e th e e le c tr o n e g a tiv ity o f c a rb o n is 2 .5 (I) a n d th e e le c tr o ­
n e g a tiv ity o f e ith e r th e m e ta ls o r th e m e ta llo id s is 2.2 (I) o r l e s s , i t
s h o u ld be e x p e c te d th a t b o n d s w ill be form ed b e tw e e n c a rb o n an d e ith e r
m e ta l o r m e ta llo id e l e m e n t s . B e c a u se o f th e v a ry in g d if f e r e n c e s in
e l e c t r o n e g a t i v i t i e s , i t s h o u ld be e x p e c te d t h a t th e re w ill b e a v a r ia tio n in
th e bond c h a r a c te r s from io n ic (w h ere th e d iffe re n c e in e le c tr o n e g a tiv ity
is la rg e ) to c o v a le n t (w h ere th e d iff e r e n c e in e le c tr o n e g a tiv ity i s s m a l l) .
In a d d itio n to io n ic a n d c o v a le n t b o n d s , a th ird ty p e o f b o n d , th e s y n e r g ic
b o n d , c a n b e form ed a n d w ill be d i s c u s s e d .
The a re a o f c h e m is try w h ic h
in v o lv e s c o m p o u n d s w ith b o n d s b e tw e e n e ith e r m e ta l o r m e ta llo id s and
c a rb o n i s c a lle d o r g a n o m e ta l lic s .
S in c e th e a lk a l i a n d a lk a lin e e a r th m e ta ls h a v e th e l a r g e s t d iff e r­
e n c e in e le c tr o n e g a tiv ity w ith r e s p e c t to c a r b o n , th e y form m o s tly io n ic .
b o n d s w ith th e b o n d 's c o v a le n t c h a r a c te r d e c r e a s in g a s th e d iffe re n c e in
e le c tr o n e g a tiv ity i n c r e a s e s .
As a r e s u l t o f th e io n ic c h a r a c te r o f th e b o n d , th e o rg a n o m e ta llic
c o m p le x e s o f th e a lk a l i a n d a lk a lin e m e ta ls sh o w th e r e p la c e m e n t r e a c tio n
s o com m only e n c o u n te re d in th e in o rg a n ic c h e m is try o f io n ic c o m p o u n d s .
C 2 H 5~Na+ + C 6H 6
-
C 6H 5~Na+ + C ^H g
(2 )
A n other ty p e o f io n ic r e a c tio n is th e d o u b le d e c o m p o s itio n r e a c tio n : ■
C gHg- Na+ +
C 2 H 5 Br
C 4 H10 + NaBr
(3) .
2
4 C 2 H 5 Na+ + SiC l4
-» .(C2 H4 ) 4Si + ' 4 N a C l
(4)
The l a s t r e a c tio n a l s o p ro v id e s a u s e f u l .s y n th e s is o r a n o rg a n o m e ta llic
co m p o u n d o f a m e ta llo id .
A n o th er m a n if e s ta tio n o f th e io n ic b o n d is th a t th e co m p o u n d s a re
e l e c t r i c a l c o n d u c to rs a n d d u rin g e le c tr o l y s is y ie ld h y d ro c a rb o n s a t th e
a n o d e an d m e ta ls a t th e c a th o d e (5 ).
O rg a n o m e ta llic c o m p le x e s o f th e a lk a lin e e a r th m e t a l s , s u c h a s th e
G rig n a rd r e a g e n t, a re com m only u s e d in th e s y n th e s is o f o rg a n ic com ­
p o u n d s to a tta c h a h y d ro c a rb o n to a n o th e r m o le c u le . U s in g th e G rig n ard
r e a g e n t t h i s i s a c c o m p lis h e d by re p la c in g a h a lo g e n w ith a h y d ro c a rb o n
m o le c u le .
RCl +
C H 3 MgBr
->
RCH3 +
M gClB r
( 6)
A n o th er u s e o f th e G rig n a rd re a g e n t is th e c o n v e rs io n o f c a rb o n y ls to
h y d ro x y ls :
R2 C=O + RMgX
->
R2 C -O -M g X + H C l
T
R3 C -O -M g X
->
R3 C -O H
(7) ’
/
T h e s e r e a c tio n s m ay be th o u g h t o f a s th e m a g n esiu m io n g iv in g up th e ■
o rg a n ic lig a n d fo r a m ore e le c tr o n e g a tiv e e le m e n t. T hus w h e n •
p h e n y llith iu m is u s e d in p la c e o f p h e n y lm a g n e siu m b ro m id e in a G rig n ard
r e a c t i o n , th e p h e n y llith iu m r e a c ts 100 tim e s f a s te r b e c a u s e lith iu m h a s a
lo w e r e le c tr o n e g a tiv ity th a n m a g n esiu m (8) .
3
W h en th e e le c tr o n e g a tiv ity d iff e r e n c e w ith r e s p e c t to c a rb o n i s l e s s
th a n 1.2 th e c o v a le n t c h a r a c te r o f th e o rg a n o m e ta llic b o n d is m ore im p o rt­
a n t in d e te rm in in g th e b o n d c h a r a c t e r i s t i c s th a n is th e io n ic bond c h a r a c ­
t e r . T hus th e o rg a n o m e ta llic c o v a le n t co m p o u n d s a re form ed by
m e t a l l o i d s . The o rg a n o m e ta llic m e ta llo id c o m p le x e s a re u n a s s o c ia te d
s ta b l e c o m p o u n d s , u n r e a c tiv e to a ir a n d w a te r , w h ic h r e s i s t c h a n g e in
m ild a c id a n d b a s e s o lu tio n s . An e x a m p le o f th is ty p e o f co m pound is
te t r a m e t h y l s i l a n e . H o w e v e r, th e re a re so m e d iff e r e n c e s from s tr ic tly
o rg a n ic r e a c tio n s d u e to : a) th e a b ility o f th e o rg a n o m e ta llic m e ta llo id
c o m p le x to u s e th e u n fille d d o r b ita ls o f th e m e ta llo id ; a n d b) th e v a ry in g
e le c tr o n d o n a tin g a b ility o f th e m e ta llo id w ith r e s p e c t to c a rb o n .
The c o v a le n tly b o n d e d o rg a n o m e ta llic m e ta llo id s a re u s u a lly p r e ­
p a re d by th e r e a c t i o n 'o f th e h a lid e o f th e m e ta llo id w ith th e so d iu m s a l t o f
th e o rg a n ic lig a n d , a s sh o w n p r e v io u s ly , o r w ith th e G rig n a rd re a g e n t and.
a h a lid e o f th e m e ta llo id .
2 PbBr2 + 4 C 2 H 5 MgBr -> (C 3 H 5) 4 Pb + 4 MgBr3 + Pb
(9)
In a d d itio n to th e c o v a le n t c o m p le x e s form ed w ith th e m e ta llo id s ,
th e re a re a ls o c o v a le n t c o m p le x e s form ed u s in g tr a n s itio n m e t a l s . T h e se
c o v a le n tly b o n d e d t r a n s itio n m e ta l o rg a n o m e ta llic c o m p le x e s a re c h a r a c ­
te r iz e d by lo w th e rm a l s t a b i l i t y an d r e a c tiv i ty to a ir a n d w a te r .
To p re p a re a c o v a le n tly b o n d e d a lk y l o r a ry l tr a n s itio n m e ta l o rg a n o ­
m e ta llic c o m p le x , a r e a c tio n is u s u a ll y ru n w ith th e tr a n s itio n m e ta l
h a lid e , w ith m e th y llith iu m o r w ith m e th y !m a g n e siu m b ro m id e .
T iI4 + 4 M eLi
T i(C H 3) 4 + 4 LiI
(10)
4
H g C l2 + C H 3 MgBr -
(C H 3) 3 Hg + MgBrg + M g C lg
(9)
The th ird ty p e o f b o n d , th e s y n e r g ic b o n d , c o n s i s t s o f tw o p a rts a s
r e p r e s e n te d in F igure I .
F ir s t o f a l l , th e re is a d o n a tio n o f pi e le c tr o n s
A
C •— —
----------- D
F ig . I . P ic to r ia l r e p r e s e n ta tio n o f th e b o n d b e tw e e n p la tin u m and
e th y le n e . The d o tte d lin e on th e C -D a x is r e p r e s e n ts th e sy m m etry a x is
o f th e o -b o n d a n d th e tw o h a tc h e d s p a c e s a b o v e a n d b e lo w th e cr-bond
r e p r e s e n t th e n - o r b ita l o f e th y le n e . Both a - an d tt- b o n d s a re o c c u p ie d by
tw o e l e c t r o n s . A round th e p la tin u m , sh o w n a s a s m a ll c ir c le in th e lo w e r
p a rt o f th e d ia g ra m on th e A-B a x i s , a re sh o w n a h y b rid e m p ty d s p g - o r b ita l
(u p w ard e llip s e ) s u p e rim p o s e d on th e o c c u p ie d n - o r b ita l o f e th y le n e ,
form ing a d a tiv e a - b o n d . The h a tc h e d a re a a ro u n d th e p la tin u m atom r e p ­
r e s e n ts th e o c c u p ie d dx z - o r b ita l (on th e p la n e o f th e d iag ram ) w h ic h is
o v e rla p p in g th e n - a n tib o n d in g o rb ita l o f e th y le n e g iv in g n - b a c k - d o n a tio n .
The a rro w s in d ic a te th e d ir e c tio n o f tr a n s f e r o f th e e le c tr o n c h a rg e d u e to
th e b o n d in g . ( 11)
from th e lig a n d to th e v a c a n t o rb ita l o f th e m e ta l. The s e c o n d p a rt c o n ­
s i s t s o f th e b a c k -b o n d in g o r flow o f e le c tr o n s from th e f ille d d o rb ita l o f
th e m e ta l to th e a n tib o n d in g o r b ita l o f th e d o u b le b o n d . A lthough th is
a n tib o n d in g o r b ita l o f th e d o u b le b o n d is a n tib o n d in g w ith r e s p e c t to th e
c a r b o n -c a rb o n b o n d , i t i s a b o n d in g o r b ita l w ith r e s p e c t to th e
5
c a r b o n - m e ta l bond a n d th u s th e b a c k - b o n d in g a d d s to th e s t a b i l i t y o f th e
c o m p le x . The n u m b e r o f d o u b le b o n d s th a t c a n be b o n d e d to a s in g le
m e ta l atom by a s y n e r g ic bond i s lim ite d by th e n u m b er o f lig a n d s th a t c a n
b e a rra n g e d so th e g e o m e try o f th e lig a n d o rb ita l m a tc h e s w ith a v a c a n t
b o n d in g o r b ita l o f th e m e ta l, by th e am o u n t o f b a c k -d o n a tio n th a t c a n
o c c u r , an d f in a lly by th e s t e r i c f a c to rs o f th e lig a n d .
O ne m eth o d o f p re p a rin g c o m p o u n d s c o n ta in in g th e s y n e r g ic b o n d is
th e d o u b le d e c o m p o s itio n r e a c tio n o u tlin e d b elo w :
.
X (C 5H 5) - Na+ + M C lx
-> M (C 5Hg)
+ xN aC l
The m e ta l c a n be v a n a d iu m , ch ro m iu m , m a n g a n e s e , ir o n , ru th e n iu m ,
c o b a lt o r n ic k e l.
A n o th er d o u b le bond s y s te m th a t c a n b e u s e d i s b e n z e n e . Thus
d ib e n z e n e chrom ium c a n b e p re p a re d a s fo llo w s :
CrC13 + C 6H6
I) A l-A lC l3
ZTN a 2 S-
,
<C 6H6>2 <*
<12>
The o rg a n ic lig a n d c a n a ls o b e a c h a in s y s te m w h e re th e d o u b le
b o n d s a re c o n ju g a te d , a s in b u ta d ie n e , o r n o n - c o n ju g a te d , a s in
e th y le n e , o r a n y o f th e m an y d e r iv a tiv e s o f th e s e s y s te m s .
S y n e rg ic b o n d s a re n o t lim ite d to b o n d s b e tw e e n p i e le c tr o n s an d
m e ta ls > b u t c a n a ls o e x i s t w ith o th e r m o le c u le s w h ic h c a n d o n a te a lo n e
p a ir o f e le c tr o n s to a v a c a n t m e ta l o r b ita l a n d a c c e p t so m e b a c k - d o n a tio n
from th e m e ta l d o r b it a l.
O ne s u c h m o le c u le i s c a rb o n m o n o x id e . W hen
c a rb o n m o n o x id e i s th e o n ly lig a n d th e c o m p le x is c a ll e d a m e ta l
c a r b o n y l. M e ta l c a r b o n y ls a re k n ow n fo r tr a n s itio n e le m e n ts from
6
G roup YB to V III. W hen a m e ta l c a rb o n y l c o n ta in s a m e ta l w ith an e v e n
a to m ic n u m b er i t m ay c o n ta in o n e o r m ore th a n o n e m e ta l a to m (s) p e r co m ­
p le x , b u t a m e ta l c a rb o n y l c o m p le x c o n ta in in g a m e ta l w ith a n odd a to m ic
n u m b e r form s c o m p le x e s w h ic h c o n ta in m ore th a n o n e m e ta l ato m p e r co m ­
p le x e x c e p t for v a n a d iu m h e x a c a r b o n y l, w h ic h h a s an o d d a to m ic nu m b er
b u t s t i l l h a s o n ly o n e m e ta l atom p e r c o m p le x . In a ll c a s e s th e m o st
s ta b l e s t a t e o f th e m e ta l c a rb o n y l o f e a c h tr a n s itio n m e ta l h a s th e e le c tr o n
c o n fig u ra tio n o f th e n o b le g a s o f w h ic h e v e r p e rio d i t is a p a r t.
The m e ta l c a rb o n y ls o f G ro u p s YB to VIII a re g e n e r a lly p re p a re d by
th e a c tio n o f c a rb o n m o n o x id e , in th e p r e s e n c e o f a re d u c in g a g e n t, on
th e m e ta l s a l t a t h ig h te m p e ra tu re an d p r e s s u r e .
2 CoCOg + 2 Hg + 8 CO -» COg(CO)g + 2 COg + 2 HgO
(13)
O n ly tw o m e ta l c a rb o n y ls c a n b e form ed d ir e c tly from th e p u re m e ta l and
c a rb o n m o n o x id e .
N i + 4 CO
-
N i(C O ) 4
(13)
Fe + 5 CO
-
F e (C O )5,
(13)
The c a rb o n y l m o le c u le is k now n to bond to m e ta ls in th re e d iffe re n t
w a y s: te r m in a l, d o u b le b rid g in g an d (ra re ly ) tr ip le b rid g in g . The m o le c u ­
l a r o r b ita l p ic tu re o f th e b o n d in g b e tw e e n th e te rm in a l c a rb o n y l and th e
m e ta l is a g a in d iv id e d in to tw o p a r ts „ The c a rb o n y l d o n a te s tw o sig m a
e le c tr o n s to th e e m p ty m e ta l h y b rid iz e d o r b ita l an d th e m e ta l d o n a te s
e le c tr o n s from i t s f ille d d o r b ita ls to th e c a rb o n y l a n tib o n d in g o r b ita l.
T his b o n d , a s b e f o r e , i s s y n e r g ic s in c e th e d rift o f e le c tr o n s from th e
c a rb o n y l to th e m e ta l m a k e s th e c a rb o n y l m ore p o s itiv e ly c h a r g e d , w h ic h
7
in tu rn m a k e s i t a b e tte r a c c e p to r o f e le c tr o n s from th e m e ta l d o r b it a l,
th u s c a n c e llin g th e p o s itiv e c h a r g e , a s sh o w n in F ig u re 2 .
F ig . 2 . (a) The fo rm a tio n o f th e m e ta l- c a r b o n cr-bond u s in g a n u n s h a re d
p a ir on C a to m . (b) The fo rm a tio n o f th e m e ta l-c a rb o n rr-b o n d . The o th e r
o r b ita ls on th e CO a re o m itte d fo r c l a r i t y . (14)
In th e c a s e o f d o u b le b rid g in g c a r b o n y ls , th e c a rb o n y l group c o n ­
tr ib u te s o n e e le c tr o n to e a c h o f th e tw o m e ta l a to m s to form n orm al sig m a
b o n d s w ith th e m e ta l a ls o d o n a tin g o n e e le c tr o n . The c a rb o n y l w ill a ls o
a c c e p t so m e b a c k - d o n a tio n from th e m e ta l in to its a n tib o n d in g o r b ita l. In
a ll th e c a s e s w h e re th e r e a re b rid g in g m e ta l c a r b o n y ls , e ith e r d o u b le o r
t r i p l e , th e re is a l s o a m e ta l- m e ta l b o n d , a s sh o w n in F ig u re 3 . T his bond
i s p r e s e n t b e c a u s e th e c a rb o n y l h o ld s th e tw o m e ta ls so c lo s e th a t th e re
i s a n o v e rla p o f o r b ita ls a n d it a ls o a llo w s th e m e ta ls to a c h ie v e a co m ­
p le te s h e ll o f e l e c t r o n s , th u s a d d in g to th e s t a b i lity o f th e c o m p le x .
A v e ry im p o rta n t a s p e c t o f m e ta l c a rb o n y ls is th a t sig m a s u b s titu te d
tr a n s itio n m e ta l c a rb o n y ls a re m uch m ore s ta b le th a n a re th e sig m a s u b ­
s titu te d tr a n s itio n m e ta ls a lo n e (16).
The in c r e a s e in s t a b i l i t y m ay be d u e
to th e re m o v a l o f th e e x c e s s e le c tr o n d e n s i t y , w h ic h i s c a u s e d by th e
8
F ig . 3 . (a) The
s tr u c tu r e p ro p o s e d for Co^(CO)Jig in s o lu tio n on th e
b a s i s o f i t s in fr a r e a s p e c tru m , (b) The s tr u c tu r e (sy m m e try T^) o f
R hg(CO )Jg d e te rm in e d e n tir e ly b y X -ra y c r y s ta llo g r a p h y . (15)
sig m a b o n d e d o rg a n ic l i g a n d s , by b a c k - d o n a tio n o f e le c tr o n s from th e
m e ta l to th e c a rb o n y l a n tib o n d in g o r b i t a l s .
The m ore s ta b le sig m a s u b s tit u te d tr a n s itio n m e ta l c a rb o n y ls a re
p re p a re d by th e u s e o f th e G rig n a rd r e a g e n t w ith th e h a lid e o f th e m e ta l
c o m p le x .
TTC5 H 5 -F e (C O )2 B r + C H 3MgBr -
TrC5H 5-F e (C O )2 C H 3 + MgBr (16)
The so d iu m s a l t o f th e c o m p le x c a n a l s o b e m ade to r e a c t w ith an o rg a n ic
h a lid e .
M n (C O )5N a + R X -
RM n(CO ) 5 + NaX
(16)
An e v e n la r g e r g ro u p o f o rg a n o m e ta llic m e ta l c a rb o n y ls a re th e p i
s u b s tit u te d tr a n s itio n m e ta l c a r b o n y ls . FIere a g a in th e p r e s e n c e o f th e
9
c a r b o n y ls a d d s s t a b i l i t y to th e c o m p le x . For e x a m p le , d ib e n z e n e
chrom ium is r e a d ily o x id iz e d in a ir to th e d e r iv a tiv e o f th e ' d ib e n z e n e
chrom ium c a t i o n , w h ile th e c o rre s p o n d in g c o m p le x , b e n z e n e chrom ium
t r i c a r b o n y l, is s ta b l e in a ir .
T h is in c r e a s e in s t a b i l i t y o f p i s u b s tit u te d tr a n s itio n m e ta l c a r ­
b o n y ls m ay a g a in be d u e to th e a b ility o f th e c a rb o n y l to a c c e p t m ore
b a c k - d o n a tio n from th e m e ta l th a n th e p i s u b s tit u te d lig a n d c a n a c c e p t.
The p i s u b s tit u te d tr a n s itio n m e ta l c a rb o n y ls c a n u s u a ll y be p r e ­
p a re d th e rm a lly from th e m e ta l c a rb o n y l a n d th e d e s ir e d lig a n d :
C 4H 6
+ F e(C O ) 5 • -
C 4 H 5F e(C O ) 3 + 2 C 0
(6)
C 7FI8
+ F e(C O ) 5 -
C 7H gF e(C O ) 3 + 2 C O
(17)
C 8H 8
+ F e(C O ) 5 ->
C gH 8F e (C O )3 + 2 CO
(18)
A lth o u g h th e r e a c tio n s o f iro n p e n ta c a r b o n y l p a r a lle l th o s e o f m o st o f th e
tr a n s itio n m e ta l c a r b o n y ls , th e re is o n e m ore im p o rta n t ty p e w h ic h is n o t
p o s s ib le w ith iro n p e n ta c a r b o n y l. T h is i s th e r e a c tio n o f a ro m a tic com ­
p o u n d s s u c h a s b e n z e n e , to lu e n e , a n ilin e w ith a G roup VI m e ta l h e x a c a r b o n y l.
M (C O )6 + A rene
,
-> A re n e M (C O ) 3 + S C O
(19)
The f a c t th a t th e a re n e i s c o n n e c te d to th e m e ta l b y i t s a ro m a tic p i
s y s te m c r e a te s a n e le c tr o n d e f ic ie n c y in th e a re n e a n d c a u s e s i t to be
l e s s p ro n e to e le c tr o p h i lic a tta c k th a n th e fre e a re n e (2 0 ) .
T h a t c o m p le x in g w ith a m e ta l c a rb o n y l d o e s d e c r e a s e th e e le c tr o n
a v a i l a b i l i t y is sh o w n by a c o m p a ris o n o f th e a c id s tr e n g th o f b e n z o ic a c id
10
w ith th a t o f b e n z o ic a c id chrom ium t r i c a r b o n y l. The pKa o f th e b e n z o ic ■
a c id chrom ium tr ic a rb o n y l i s 4.77, c o m p ared to pKa 5.6 8 fo r b e n z o ic a c id .
T hus w e s e e t h a t b e n z o ic a c id chrom ium tric a rb o n y l w ill a c t m uch th e
sa m e a s n itr o b e n z o ic a c i d , w h ic h h a s a pKa o f 4 .4 8 (2 0 ).
In a d d itio n to c a u s in g th e a re n e rin g to b e l e s s r e a c tiv e to w a rd
e le c tr o p h ile in g e n e r a l , a re n e m e ta l c a rb o n y ls a re a ls o u n s ta b le to s tro n g
a c id s a n d th u s a re n o t a b le to w ith s ta n d th e r e a c tio n c o n d itio n s fo r n i t r a ­
tio n a n d s u lf o n a tio n (2 0) .
I t is s t i l l p o s s i b l e , th o u g h , to a d d m an y s u b s tit u e n ts s u c h a s
h a l i d e , n i t r a t e , h y d ro x id e an d am in e in d ir e c tly to an a re n e rin g w h en i t is
a tta c h e d to a m e ta l. O ne s u c c e s s f u l m e th o d is to tr e a t th e a re n e m e ta l
w ith a n a lk a l i m e ta l r e a g e n t s u c h a s n -a m y l so d iu m . T h is m e ta la te d
s p e c ie s c a n th e n a tta c k a n e le c tr o p h ilic m o le c u le to form a s u b s titu te d
a re n e m e ta l (21) .
COgCHg
+
^ 2CHg
(Jo2CHg
CO2 CH3
By th e sa m e r e a s o n in g w h ic h w a s u s e d to e x p la in th e d e c r e a s e in
r e a c tiv i ty o f a re n e m e ta l c a r b o n y ls , i t is e v id e n t th a t th e n u c le o p h ilic
11
a tta c k on th e a re n e w ill be e n h a n c e d . T h is id e a is a ls o s u p p o rte d b y th e
n u c le o p h ilic d is p la c e m e n t r e a c tio n o f fu n c tio n a l g ro u p s w h ic h h a v e b e e n
d e s c r ib e d to p ro c e e d in th e p i c o m p le x e d a re n e b u t do n o t p ro c e e d in an
u n c o m p le x e d a re n e (2 2 ) .
C 6H 5 C lC r(C O ) 3 + N aO C H 3 -
(C 5H 5 -O C H 3)-C r(C O ) 3 + N a C l
(22)
A n o th er im p o rta n t r e a c tio n o f m e ta l c a rb o n y ls is th e d is p la c e m e n t o f
th e c a rb o n y l group by a n o th e r sig m a d o n o r. The sig m a d o n o r w ith th e
a b ility to a c c e p t b a c k - b o n d in g s u c h a s CN , A sP h3 , S b P h 3 , SR3 , PX3 , o r
P(OR) 3 c a n d is p la c e o n e o r m ore c a rb o n y ls (2 3 ).
F e(C O ) 5 + P h 3P -> F e (P h 3P)2 (C O ) 3 + F eP h 3 (C O ) 4
(24)
In th e p r e s e n c e o f a m in e , n itr o g e n o r o x y g e n l i g a n d s , iro n
p e n ta c a rb o n y l w ill u n d e rg o a d i s s o c ia tio n re a c tio n :
2 F e(C O ) 5 + 6 a m in e -> [F e (a m in e )g ] 2+ [F e (C O )4 ] 2_ + 6 CO
(24)
w h ile m olybdenum h e x a c a rb o n y l w ill form a s e r ie s o f s ig m a c o m p le x e s :
M o(C O ) 6 + p y rid in e
-» M o (p y rid in e )(C O ) 5 + M o (P y rid in e )3 (C O )4 +
M p (P y rid in e )3 (CO ) 3
(24)
A d iff e r e n t ty p e o f r e a c tio n i s th e fo rm a tio n o f p o ly n u c le a r co m ­
p le x e s o f th e s ta r tin g m e ta l c a r b o n y l. In th e c a s e o f ir o n , th e re a re twop o ly n u c le a r c o m p le x e s know n:
F e(C O ) 5
F e(G Q ) 5
FegtCCOg
(24)
F e 3 (CO ) 12
(2 4 ).
12
In m an y c a s e s w h e re iro n p e n ta c a rb o n y l i s o n e o f th e r e a c t a n t s , th e
a c tu a l r e a c tin g s p e c ie s m ay be o n e o f th e p o ly n u c le a r c o m p le x e s sh o w n
above.
A n o th e r ty p e o f r e a c tio n is th e tr a n s f e r o f a c a rb o n y l group from th e
t r a n s itio n m e ta l to a lig a n d a tta c h e d to th e m e ta l c a r b o n y l. T his r e a c tio n
is d e m o n s tra te d by th e oxo p r o c e s s re p o rte d f ir s t by R o elen in 1938 (2 5 ).
All G roup VIII tr a n s itio n m e ta ls h a v e b e e n sh o w n to u n d e rg o th is ty p e o f
r e a c tio n (2 5 ). T his r e a c tio n is u s e d c o m m e rc ia lly w ith d ic o b a lt
o c ta c a r b o n y l to m ak e a ld e h y d e s a t p r e s s u r e s o f 100 to 200 a tm o s p h e re s
w ith a 1:1 m ix tu re o f h y d ro g e n an d c a rb o n m o n o x id e a n d a t a te m p e ra tu re
b e tw e e n IOO0 C a n d 15 0 ° C . At lo w e r p r e s s u r e an d te m p e ra tu re s th e y ie ld
i s c o rre s p o n d in g ly lo w e r.
A m e c h a n is m h a s b e e n p ro p o s e d fo r th is r e a c tio n b y H e ck and
B re slo w a n d i s o u tlin e d b e lo w (2 6).
13
O xo P r o c e s s
Cog(CO)Q + Hg
HCo(CO) ^ #
-» ZHCo(CO)^
HCo(CO) g CO
RCHg=CHg + H C o(C O ) 3 ^ R-CHyCHg
H C o(C O )3
RCH=CHg
# RCHgCHgCo(CO) 3
H C o(C O ) 3
RCHgCHgCo(CO) 3 + CO # RCH gC H gC o(C O ),
RCHgCHgCo(CO) 3 + CO
7
* R C H gC H gC O C o(C O ) 3
O
RCHgCHgCOCo(CO)3 + Hg # RCHgCHgC + H Co(CO) 3
H
The m o st im p o rta n t s te p o f th e o xo r e a c tio n i s th e c a rb o n y l in s e r tio n
b e tw e e n th e m e ta l an d th e h y d ro c a rb o n y l lig a n d . S im ila r r e a c tio n s a re o b ­
s e r v e d in th e m e ta l a lk y l c o m p le x e s s u c h a s th o s e l i s t e d b elo w :
(RgP)gPt(CH3)g + 2C O
# (RgP)3Pt(COCHg) 3
C H 3 M n (C O )5 '+ P h 3P ' * C H 3 C O M n(C O )4 P h 3P
(27)
(27)
C o m p le x e s o f N o rb o rn a d ie n e an d T r a n s itio n M e ta ls
The f i r s t re p o rte d c o m p le x b e tw e e n n o rb o rn a d ie n e
( b ic y c lo [ 2 .2 .1 ] h e p ta d ie n e - 2 ,5 ) a n d a tr a n s itio n m e ta l w a s re p o rte d by
B u rto n , G re e n , A bel a n d W ilk in s o n in 1958 (2 8 ). T hey re p o rte d th e
th e rm a l r e a c tio n o f n o rb o rn a d ie n e w ith iro n p e n ta c a r b o n y l, form ing
n o rb o rn a d ie n e iro n tr ic a r b o n y l. T h is r e a c tio n sh o w e d t h a t n o rb o rn a d ie n e
14'
c o u ld be u s e d a s a lig a n d b u t w a s a ls o th e f i r s t . c a s e o f a " n o n " c o n ju g a te d d ie n e s y s te m form ing s u c h a m e ta l p i c o m p le x .
S in c e th is f i r s t re p o rt o f a n o rb o rn a d ie n e tr a n s itio n m e ta l c o m p le x ,
n o rb o rn a d ie n e h a s b e e n sh o w n to form c o m p le x e s w ith e le v e n o th e r t r a n s ­
itio n m e t a l s . ■
A to t a l o f e ig h te e n c o m p le x e s h a v e b e e n id e n tif ie d a n d a re l i s t e d
in T a b le I .
T a b le I
T r a n s itio n M e ta l C o m p le x e s w ith N o rb o rn a d ie n e
C 7H 8F e(C O ) 3
C o g fC O y C y H g ^
C og(C O )8C 7H8
C 7H 8P d C l2
C 7H 8P tC l3
(28)
(29)
(29)
(30)
[ C 7H 8R h C lJ 2
(30)
C 7H8(AgNOs) 2
(30)
(30)
C 7H 8 M o(C O ) 4
(31)
C 7H8 Cr(CO) 4
(32)
C 7H8W(CO) 4
(32)
C 7H 8IrC l
(33)
C 7H 8Au2 C l4
(34)
C 7H 8R uC l2
(30)
(C yH g)2Au2 C l4
(34)
C 7H 8RuBr2
(30) .
(C 7H 8) 3Au2 C l4
(34)
C 7H 8 (CuBr) 2 ' (30)
■ C 7H 8 C uC l
(35)
D im er an d T rim er o f N o rb o rn a d ie n e
T h ere a r e , i f o n e c o n s id e r s s te r e o c h e m is t r y , o v e r a h u n d re d d if f e r ­
e n t w a y s to form d im e rs an d trim e rs o f n o rb o rn a d ie n e a n d , i f o n e in c lu d e s
15
th e p o s s ib le k e t o n e s , th e num ber o f co m p o u n d s w ill b e m uch la r g e r . T h is
p ro b lem o f so m any p o s s ib le is o m e rs is n o t a s e r io u s o n e in th e m e ta l
c a rb o n y l c a ta ly z e d d im e riz a tio n o f n o rb o rn a d ie n e s in c e s t e r i c fa c to rs
e lim in a te m any o f th e p o s s ib le s tr u c tu r e s an d th u s fa r e le v e n co m p o u n d s
h a v e b e e n fo u n d .
The s tr u c tu r e s o f th e c o m p o u n d s th a t h a v e b e e n fo u n d a re sh o w n in
T a b le II w ith th e ir s te r e o c h e m is tr y in d ic a te d if i t h a s b e e n d e te rm in e d .
T a b le II
D im ers an d T rim ers o f K eto n es o f N o rb o rn a d ie n e
I
II
m .p . 8 5 °C (31, 36)
m .p . 1 9 6 °C (36)
16
T ab le II ( c e n t . )
m .p . 218°C (36)
n . m . r . .87, 1 .2 3 , 1.67, 1 .8 9 , 2 .0 8
e x o tr a n s ex o p e n ta c y c lo ( 8 . 2 . 1 . 14, 7. 02 ,9. 0 3 , 8 )
te tr a d e c a d ie n e
(38)
e x o tra n s e n d o p e n ta c y c lo ( 8 . 2 . 1 . 1 4 ,7 . O2 ' 9. O3' 8)
te tr a d e c a d ie n e
(38)
m . p . 67°C
m .p . o il
n . m . r . 1 .2 3 , 1.32 , 1.69 , 2 .6 2 , 5.97
n . m .r . 1 ,1 3 , 2 .0 0 , 2 .5 4 , 2. 80 ,
5.82 , 6.20
e n d o tr a n s en d o p e n ta c y c lo ( 8 . 2 . 1 . 14 ' 7. 02 ' 9. 0 3' 8)
te tr a d e c a d ie n e
(38)
m .p . 9 2 °C
n . m . r . 1 .0 2 , 1 .5 5 , 1 .8 5 , 2 .7 2 , 6.25
■e n d o c i s e n d o h e p ta c y c lo ( 5 . 3 , 1 . 13 ,6 . 4 4 ' 12. 19' 11. O3' 5. O8' 10)
te tr a d e c a n e
■ 1 m .p . 6 5 °C
(39)
17
T a b le II ( c e n t.)
IX
X
h e p ta c y c lo -
h e p ta c y c lo -
( 5 . 5 . 1 . 14,10. O2 ,6 . o 3 ' 1 1 . o 5 ' 9 . O8,12)
( 7 ,4 .1 0 2 ' 8. 0 3” 7. O4' 12. O6,11. O10,13)
te tr a d e c a n e
te tr a d e c a n e
(39, 40)
(39, 40)
m .p . I 6 5 °C
n . m . r . 1 .7 9 , 2.45
n . m . r . .8 0 , 1 .2 8 , 1 .8 8 , 2 .3 7 , 2 .5 5 ,
6.05 (37)
n . m . r . .3 5 , 1 .1 5 , 1 .5 3 , 1 .7 8 , 2 .0 0 ,
2 .5 8 , 5 .3 0
(37)
18
M e ta l C a rb o n y l C a ta ly z e d D im e riz a tio n o f N o rb o m a d ie n e
T herm al D im e riz a tio n
i
The m e ta l c a rb o n y l c a ta ly z e d th e rm a l d im e riz a tio n o f n o rb o rn a d ie n e
w a s f i r s t re p o rte d by P e tit in 1958 (3 1 ). P e t i t fo u n d w h e n n o rb o rn a d ie n e
w a s re flu x e d w ith iro n p e n ta c a rb o n y l fo r fif te e n h o u rs a n d th e n f r a c tio n ­
a lly d i s t i l l e d th e p ro d u c ts w e re n o rb o rn a d ie n e iro n tric a rb o n y l an d a
k e to n e d im e r. The k e to n e w a s o b ta in e d a s w h ite n e e d le s from a lc o h o l,
m e ltin g p o in t 8 2 °C ( I ) .
B ird , C o o k so n an d H u d a c (41) in th e fo llo w in g y e a r sh o w e d th a t
n o rb o rn a d ie n e a n d iro n p e n ta c a rb o n y l r e a c te d to g i v e , in a d d itio n to
n o rb o rn a d ie n e iro n tr ic a r b o n y l, th re e k e to n e s (I, I I , III). B ird , C o o k so n
a n d H u d a c (41) a ls o re p o rte d th a t n ic k e l te tr a c a r b o n y l d im e riz e d n o r­
b o rn a d ie n e to g iv e tw o h y d r o c a r b o n s , w h ic h w e re te n t a t i v e l y a s s ig n e d to
c o m p o u n d s VII a n d X I. The co m p o u n d a s s ig n e d to s tr u c tu r e XI w a s l a t e r
c h a n g e d to s tr u c tu r e VI by C a n n e ll (4 2 ), b a s e d on n u c le a r m a g n e tic
re so n a n c e s tu d ie s .
L im al a n d Shim (40) in 19 61 w e re a b le to sh o w t h a t a s a tu r a te d
h y d ro c a rb o n d im e r o f n o rb o rn a d ie n e w a s fo rm ed w h en a m ix tu re o f iro n
p e n ta c a r b o n y l a n d n o rb o rn a d ie n e w a s ir r a d ia te d w ith a s u n la m p .
C o o k so n (41) h a d sh o w n th e sa m e d im e r w a s form ed th e rm a lly from iro n
e n n e c a rb o n y l in n o rb o r n a d ie n e . S in c e th e p h o to re a c tio n o f iro n p e n ta ­
c a rb o n y l form ing iro n e n n e c a rb o n y l w a s k n o w n (4 3 ), L im al a n d Shim
p o s tu la te d t h a t th e lig h t c a u s e d th e fo rm a tio n o f iro n e n n e c a rb o n y l w h ic h
th e n c a ta ly z e d th e th e rm a l r e a c tio n o f n o rb o rn a d ie n e h y d ro c a rb o n to g iv e
19
th e s a tu r a te d d im e r. T here w a s so m e d if f ic u lty in d e c id in g if th e s a t u r ­
a te d d im e r w a s s tr u c tu r e IX o r X. It w a s f in a lly c o n c lu d e d b y Katz and
A cton (44), on th e b a s i s t h a t a n id e n tic a l c a g e c o u ld be form ed from XIII
a n d h y d ro io d ic a c i d , th a t th e c o r r e c t c a g e s tr u c tu r e w a s IX.
B ird , C o l i n e s e , C o o k s o n , H u d e c a n d W illia m (4 1 ), in th e ir p a p e r
d e s c r ib in g th e fo rm a tio n o f a s a tu r a te d c a rb o n y l from iro n e n n e c a r b o n y l,
a ls o d i s c u s s th e fo llo w in g th e rm a l r e a c tio n s o f n o rb o rn a d ie n e :
F e (C O ) 5 + CyH g
-
I + II + III + V + IX + XII + XIII
F e 2 (C O ) 9 + CyH g
-
I + II + III + V + IX + XII + XIII
F e 3(C O )12 + CyH g
-
I + II + III + V + IX + XII + XIII
C o 2 (C O ) 8 + C y H 8
-
I + II + III + V + IX + XII + XIII
An in s ig h t in to th e m e c h a n ism o f th e th e rm a l d im e riz a tio n re a c tio n
o f n o rb o rn a d ie n e u s in g m e ta l c a rb o n y l a s a c a t a l y s t i s p ro v id e d by u s in g
iro n d ic a rb o n y l d in itr o s y l a s th e c a t a l y s t (4 5 ). From th e la rg e num ber o f
iro n d in itr o s y l c o m p le x e s th a t c a n b e p re p a re d u s in g iro n d ic a rb o n y l
d in itr o s y l, i t i s e v id e n t th a t th e c a rb o n y l g ro u p s c a n b e r e p la c e d more
e a s i l y th a n th e n itr o s y l g ro u p . In th e r e a c tio n o f iro n d ic a rb o n y l
20
d in itr o s y l a n d n o rb o rn a d ie n e th e a p p e a r a n c e o f an in fra re d p e a k a t
-I
1745 cm in d ic a te s th e fo rm a tio n o f a c o m p le x b e tw e e n iro n d in itr o s y l
a n d n o r b o r n a d ie n e . It h a s b e e n p ro p o s e d (45) th a t th e c o m p le x b e tw e e n
tw o n o rb o r n a d ie n e s a n d iro n d in itr o s y l m ay b e form ed b y h a v in g o n e o f
th e d o u b le b o n d s on e a c h n o rb o rn a d ie n e r e p la c e o n e c a rb o n m o n o x id e .
If th e c o m p le x i s form ed by s u c c e s s i v e r e p la c e m e n t o f th e c a rb o n
m o n o x id e lig a n d by th e d o u b le b o n d o f n o r b o r n a d ie n e , th e re p la c e m e n t o f
th e c a rb o n m o n o x id e by tr ip h e n y lp h o s p h in e sh o u ld s to p th e fo rm atio n o f
th e c o m p le x s in c e trip h e n y lp h o s p h in e lig a n d s a re n o t r e p la c e b y d o u b le
b o n d s (4 5 ). The r e a c tio n o f iro n d in itr o s y l b is trip h e n y lp h o s .p h in e h a s
b e e n tr ie d a n d no d im e r p ro d u c ts a re fo rm ed u n d e r s im ila r r e a c tio n c o n d i­
tio n s u s e d fo r th e iro n d in itr o s y l d i c a rb o n y l r e a c tio n .
The d im e riz a tio n c a n th e n b e v is u a l iz e d a s o c c u rrin g in tr a m o le c u la r ly b e tw e e n tw o n o rb o r n a d ie n e s a tta c h e d to a n iro n d in itr o s y l in a
s t e r i c a l l y c r i t i c a l te tr a h e d r a l c o m p le x s t r u c t u r e . A lth o u g h o n ly o n e p i
b o n d from e a c h n o rb o rn a d ie n e m o le c u le i s fo rm ally i n v o lv e d , th e la c k o f
a d im e r w h e n n o rb o rn e n e i s u s e d (45) s u g g e s ts th e s e c o n d p i bond o f
n o rb o rn a d ie n e a ls o c o n tr ib u te s to th e tr a n s itio n s t a t e , . ■
In th e c a s e o f c o b a lt tric a rb o n y l n itr o s y l (45) th e r e i s th e p o s s i ­
b ility o f re p la c in g th r e e lig a n d s in s t e a d o f j u s t tw o . If a l l th re e
c a rb o n y ls w e re r e p la c e d , th is w o u ld a llo w fo r o n e n o rb o rn a d ie n e to be
d o u b ly b o n d e d to th e t r a n s itio n m e ta l a n d o n e s in g ly b o n d e d . From th is
in te r m e d ia te o n e w o u ld e x p e c t o n e o f th e m a jo r p ro d u c ts to b e a
n o r tr ic y c le n e ty p e d im e r (XII, X III). The m a jo r p ro d u c ts a re a
21
n o r tr ic y c le n e ty p e d im e r a n d th e exo tr a n s exo d im e r (V) in a d d itio n th e re
is a tr a c e o f d im e r VI fo u n d „
The fo rm a tio n o f a h ex o tr a n s ex o d im e r a n d a n o r tr ic y c le n e ty p e
d im e r in th e r e a c tio n o f c o b a lt tric a rb o n y l n itr o s y l (45) d e m o n s tra te s a n ­
o th e r i n te r e s t in g f a c t . A c co rd in g to th e W o o d w ard -H o ffm a n r u le s (46, 47,
4 8 ), th e fo rm a tio n o f ex o tr a n s exo ty p e d im e rs s h o u ld b e th e rm a lly fo r­
b id d e n w h e re th e fo rm a tio n o f n o rtr ic y c le n e ty p e d im e rs s h o u ld be
th e rm a lly a llo w e d (46, 47, 4 8 ). The f a c t th a t b o th ty p e s o f d im e rs are
fo rm ed th e rm a lly in th e p r e s e n c e o f a tr a n s itio n m e ta l c a t a l y s t in d ic a te s
t h a t th e W o o d w ard -H o ffm a n sy m m etry r e s tr ic tio n s , do n o t a p p ly (46, 47,
4 8 ). T his c h a n g e in r e s tr ic tio n m ay b e d u e to th e m ix in g o f th e e th y le n e
c a r b o n 's 2 P tt o r b ita l w ith th e m e ta l d o r b it a l. The a to m ic d o r b ita ls o f
th e m e ta l a llo w th e e le c tr o n s o f th e h y d ro c a rb o n lig a n d a n d th e m e ta l
e le c tr o n s to m ix an d f ill th e re q u ire d re g io n o f s p a c e fo r d im e riz a tio n o f
th e lig a n d to o c c u r . T h at b o th ty p e s o f d im e r a re form ed is fu rth e r e v i­
d e n c e o f a tr a n s itio n s t a t e in v o lv in g tw o n o rb o rn a d ie n e s an d a tr a n s itio n
m e ta l. The ro le o f th e m e ta l in th is c a s e is th e re fo re th e re m o v a l o f th e
sy m m e try r e s t r i c t i o n s a n d th e lo w e rin g o f th e a c tiv a tio n e n e r g y .
A n o th er p o s s ib le w a y to e x p la in th e fo rm atio n o f th e th e rm a lly fo r­
b id d e n ex o tr a n s ex o d im e r in th e th e rm a l e x p e rim e n t is to in v o k e a n o n c o n c e rte d m e c h a n is m . The n o n - c o n c e r te d m e c h a n ism is p ro p o s e d for th e
fo rm a tio n o f d im e r p ro d u c ts u s in g rh o d iu m on. c a rb o n a s th e c a t a l y s t . .
K atz an d M ro w ca (37) in v e s t ig a te d th is r e a c tio n an d fo u n d th e th e rm a l
22
p ro d u c ts to b e X II, X III, IV an d a tr a c e o f V. The rh o d iu m -c a rb o n c a t a l y s t
i s v e ry e f f e c t iv e , g iv in g p ro d u c ts q u a n tita tiv e ly an d q u ic k ly a t room
te m p e r a tu r e .
-Katz a n d A cton (44) h a v e in v e s tig a te d th e r e a c tio n o f rhodium on
c a rb o n fu r th e r an d h a v e re p o rte d a form al r e la tio n s h ip b e tw e e n tw o p a ir s
o f th e re p o rte d h y d ro c a rb o n d im e r s . T h ey fu rth e r s u g g e s t t h a t in th e
m e ta l c a ta ly z e d c y c lo a d d itio n r e a c tio n s a n in te rm e d ia te is p ro d u c e d in
w h ic h o n ly o n e c a rb o n to c a rb o n bond i s form ed u n itin g th e tw o n o rb o rn a d i e n e s . R o ta tio n c a n o c c u r a b o u t th is s in g le bond b e fo re th e s e c o n d b o n d
c l o s e s . T h is m e c h a n is m a llo w s th e D ie ls - A ld e r p ro d u c t a n d th e o th e r
h y d ro c a rb o n d im e r to a r i s e from th e sa m e in te r m e d ia te . I f th e s e c o n d
b o n d c l o s e s w ith o u t r o ta tio n a b o u t th e i n i t i a l b o n d th e p ro d u c ts a re V, VI
a n d V II. If r o ta tio n o f 9 0 ° o c c u rs a b o u t th e i n i t i a l b o n d th e p ro d u c ts a re
XII a n d XIII (F ig u re 4 ).
A r e a c tio n o f 30% p a lla d iu m on c a rb o n g iv e s a .1% y ie ld o f d im e r I
w h ile b o th .5% p la tin u m on c h a r c o a l a n d th e n ic k e l c a t a l y s t f a ile d to g iv e
a n y p ro d u c t w h e n ru n u n d e r s im ila r r e a c tio n c o n d itio n s (4 4 ).
Two o th e r m e ta l c a rb o n y ls h a v e b e e n sh o w n to c a ta ly z e a th e rm a l
r e a c tio n o f n o rb o rn a d i e n e . M o ly b d en u m h e x a c a rb o n y l (50) an d tu n g s te n
h e x a c a rb o n y l (50) h a v e b o th b e e n sh o w n to a c t a s c a t a l y s t s fo r th e p o ly ­
m e riz a tio n o f n o r b o r n a d ie n e . The p o ly m e r th a t is fo rm ed i s a w h ite s o l i d ,
s ta b l e to g r e a te r th a n 3 5 O0 C a t a tm o s p h e ric p r e s s u r e a n d i s form ed w h en
n o rb o rn a d ie n e is re flu x e d in to lu e n e fo r 21 h o u rs w ith e ith e r m olybdenum
o r tu n g s te n h e x a c a r b o n y l. The r e a c tio n m ix tu re o f m e ta l h e x a c a rb o n y l
23
X II
X III
F ig . 4 . N o n - c o n c e r te d m e c h a n is m p ro p o s e d fo r th e fo rm a tio n o f d im er
p ro d u c ts u s in g rho d iu m on c a rb o n a s th e c a t a l y s t (4 4 ).
a n d n o rb o rn a d ie n e s h o u ld be a n h y d ro u s a n d free o f o x y g e n fo r th e h ig h e s t
y ie ld .
P h o to c h e m ic a l D im e riz a tio n
The p h o to c h e m ic a l r e a c tio n s o f n o rb o rn a d ie n e a n d m e ta l c a rb o n y ls
h a v e n o t b e e n s tu d ie d a s e x te n s iv e ly a s th e c o rre s p o n d in g ly th e rm a l
r e a c t i o n s . The f a c t t h a t lig h t w o u ld c a u s e d im e riz a tio n w a s f ir s t re p o rte d
in 19 58 by P e tit (31). P e tit sh o w e d t h a t iro n p e n ta c a rb o n y l a n d n o rb o rn a ­
d ie n e in s u n lig h t for fiv e h o u rs g a v e n o rb o rn a d ie n e iro n tr i c a r b o n y l, a
k e to n e (I) an d a s o lid h y d ro c a rb o n d im e r w ith a m e ltin g p o in t o f 6 7 - 6 8 ° C
(V ).
24
I t h a s now b e e n sh o w n (51) t h a t i f s u b s tit u te d o r u n s u b s titu te d
b u ta d ie n e iro n tr ic a r b o n y ls a re u s e d a s a c a t a l y s t for th e p h o to c h e m ic a l
d im e riz a tio n o f n o r b o r n a d ie n e , th e p ro d u c ts a re ex o tr a n s ex o (V) and
e n d o tr a n s e n d o (V II). T his c h a n g e o f p h o to c h e m ic a l p ro d u c ts from th e
u s e o f iro n p e n ta c a rb o n y l a s th e c a t a l y s t s u g g e s ts t h a t c h a n g e s in th e
n u m b er o f c a rb o n y ls o r s te r e o c h e m is tr y o r b o th m ay b e a n im p o rta n t f a c ­
to r in d e te rm in in g th e f in a l r e a c tio n p r o d u c t s .
The fo llo w in g in v e s t ig a ti o n w a s in i t i a t e d to d e te rm in e : a) th e
p h o to c h e m ic a l m e c h a n is m o f th e d im e riz a tio n o f n o rb o rn a d ie n e u s in g
m e ta l c a r b o n y ls ; b) th e e f f e c t o f th e s t e r i c fa c to rs o f th e lig a n d on th e
p ro d u c t i d e n t i t i e s a n d th e p ro d u c t r a tio s ; c) th e e f f e c t o f th e num ber o f
c a r b o n y ls on th e p ro d u c t i d e n titie s a n d th e p ro d u c t r a t i o s .
DISCUSSION
To b e g in th e in v e s t ig a ti o n o f th e s t e r i c e f f e c ts an d th e e f f e c t o f th e
n u m b e r o f c a rb o n y ls on m e ta l c a rb o n y l c a ta ly z e d d im e riz a tio n o f n o rb o rn a d ie n e a n d to d e te rm in e th e p h o to c h e m ic a l m e c h a n is m o f th is r e a c tio n , i t
w a s n e c e s s a r y to c h o o s e a tr a n s itio n m e ta l c a rb o n y l to a c t a s a r e a c ta n t
te m p la te . The tr a n s itio n m e ta l s h o u ld b e a b le to form s ta b le c o m p le x e s
n o t o n ly w ith c a rb o n y ls b u t a ls o w ith o rg a n ic lig a n d s w h ic h w o u ld a llo w
for a v a r ia tio n in s t e r i c f a c t o r s . C hrom ium w a s th e t r a n s itio n m e ta l
c h o s e n b e c a u s e i t form s chrom ium h e x a c a r b o n y l, n o rb o rn a d ie n e chrom ium
t e t r a c a rb o n y l a n d a ls o a s e r i e s o f b e n z e n e - s u b s t i t u t e d chrom ium
t r i c a r b o n y l s . In a d d itio n , th e n u m b er o f c a rb o n y ls c o u ld b e v a rie d e v e n
fu r th e r s in c e th e r e is th e a ir - u n s t a b l e d ic u m e n e c h ro m iu m . The fo llo w in g
s e r i e s 'o f chrom ium c o m p le x e s w e re c h o s e n a s th e p h o to c h e m ic a l r e a c ta n t
te m p la te s .
T a b le III
M e ta l C a rb o n y l R e a c ta n t T e m p la te s
C hrom ium h e x a c a rb o n y l
Cr(CO),
In fra re d s p e c tru m 1988 cm ^
(52)
U ltr a v io le t s p e c tru m 230 (lo g s 4 .7 8 ) , 280
(lo g s 4 .0 7 ) , 318
(lo g s 3 .49)
(53)
N o rb o rn a d ie n e chrom ium tr ic a rb o n y l
C r(C O )zJ
-I
In fra re d s p e c tru m 1913, 1944, 195 8 , 2 033 cm
N u c le a r m a g n e tic r e s o n a n p e 4.4 2 , 3. 73 , I. 30 (54)
26
T a b le III ( c o n t .)
B en z e n e chrom ium tric a rb o n y l
In fra re d s p e c tru m 1 9 1 0 , 1983 cm ^
U ltr a v io le t sp e c tru m 218 (lo g s 4 .4 3 ) ,
264 Uoge 3.92,
316 (lo g s 4 .0 5
(53)
T o lu en e chrom ium tric a rb o n y l
C r(C O ).
-I
In fra re d s p e c tru m 1 9 0 0 , 1971 cm
U ltr a v io le t sp e c tru m 218 (lo g s 4 .0 5 ),
261 (lo g s 3 .9 7 ) ,
318 (logs 4.12)
(53)
M e s ity le n e chrom ium tric a rb o n y l
In fra re d s p e c tru m 1 8 8 9 , 19 63 cm ^
U ltr a v io le t s p e c tru m 215 (lo g e 4 .4 8 ) ,
253 (lo g s 4 .0 2 ) ,
312 (loge 4 .0 8 ) (56)
D ic u m e n e chrom ium
Cr
2
The in fra re d - b a n d s b e tw e e n 1 8 5 0 -2 0 5 0 cm * a re c h a r a c t e r i s t i c o f a ll m e ta l
c a rb o n y ls an d a re a s s ig n e d to th e c a r b o n -o x y g e n s tr e tc h in g fre q u e n c y
(5 7 ).
27
The u ltr a v io le t s p e c tr a a re a ls o v e ry c h a r a c t e r i s t i c o f th e m e ta l
c a r b o n y ls . The 230 m p a n d 2 80 m p b a n d s a re a ttr ib u te d to th e m e ta l to
lig a n d c h a rg e tr a n s f e r (1A -> 1T ) (5 8 ). The b a n d in th e 320 m p re g io n
Ig
Ig
i s d u e to th e d->d tr a n s i t i o n a n d is v e ry d if f ic u lt to lo c a t e s in c e th e
lig a n d to m e ta l c h a rg e tr a n s f e r s a re in te n s e in th is re g io n o f th e u l t r a ­
v i o l e t . The r e a s o n th e d -* d tr a n s itio n s a re in th is re g io n a n d n o t a t
lo n g e r w a v e le n g th s i s th a t th e c a rb o n y ls c a u s e , a la rg e c ry s ta l, fie ld
s p littin g (5 9 ).
The i n i t i a l e x p e rim e n ts w e re to d e te rm in e if th e chrom ium com ­
p le x e s c o u ld a c t a s p h o to c h e m ic a l r e a c t a n t te m p la te s a n d to d e te rm in e
th e p h o to c h e m ic a l p r o d u c t s , if a n y .
P ro c e d u re fo r D e te rm in in g P ro d u c ts a n d P ro d u c t R atio s
The g e n e r a l p ro c e d u re (T ab le IV) w a s to m ake a s o lu tio n o f th e
m e ta l c a rb o n y l in 70 ml o f f r e s h ly d i s t i l l e d n o r b o r n a d ie n e . T h is s o lu tio n
w a s p u t in to th e la rg e r e a c tio n v e s s e l a n d p u rifie d n itr o g e n w a s b u b b le d
th ro u g h th e s o lu tio n fo r 12 h o u r s . The ir r a d ia tio n w a s s ta r te d an d th e
s a m p le ir r a d ia te d u s in g a c o re x f i l t e r fo r a p p ro x im a te ly 24 h o u r s . In fra ­
re d a n d g a s c h ro m a to g ra p h s w e re ru n o n th e to ta l r e a c tio n p ro d u c t. The
r e a c tio n m ix tu re w a s th e n f ilte r e d th ro u g h a c tiv a te d a lu m in a an d w a s h e d
w ith h e x a n e . T his s o lu tio n w a s c o n c e n tr a te d to rem ove th e h e x a n e an d
th e n ru n th ro u g h th e A e ro g ra p h A utoprep a n d s e p a r a te d . In te g ra tio n o f th e
p e a k s u s in g a S a rg e n t M o d el SR re c o rd e r g a v e th e p ro d u c t r a t i o s . F ive
s e p a r a te f r a c tio n s w e re c o lle c te d a n d id e n tif ie d .
th re e c o m p o n e n ts .
F ra c tio n fiv e c o n ta in e d
28
T a b le IV
E x p e rim e n ta l P ro c e d u re fo r P ro d u c t I d e n tif ic a tio n
M (CO) g in n o rb o rn a d ie n e
KL b u b b le d th ro u g h
12 h o u rs
Ir ra d ia tio n (c o re x filte r)
ir r a d ia te d
In fra re d a n d g a s
c h ro m a to g ra p h
S o lu tio n f ilte r e d
a n d th e n c o n c e n tr a te d
I
I n je c tio n in to
A u to p rep
F ra c tio n I
F ra c tio n III
F ra c tio n V
L iq u id
O il
S o lv e n t
N u c le a r M a g n e tic R e s o n a n c e
I
F ra c tio n II
F ra c tio n IV
I
W h ite s o lid
T-
N u c le a r m a g n e tic
re s o n a n c e
M e ltin g p o in t
I
N u c le a r m a g n e tic re s o n a n c e
G as c h ro m a to g ra p h
G a s c h ro m a to g ra p h
T
C o m p o n en t II
W h iti s o lid
M e ltin g "po in t > 3 0 0 °C
M a s s s5jPf
p e c tru m
C om ponent I
In fra re d
W h ite | s o lid
N u c le a r m a g n e tic re s o n a n c e
M a s s sp e c tru m
C o m p o n e n t III
No in v e s tig a tio n
29
F ra c tio n o n e r e p r e s e n te d a ll th e m a te ria l th a t cam e o ff th e 30%
S E -30 co lu m n b e fo re th e f i r s t d im e r, w h ic h w as d e te c te d 88 m in u te s a f te r
th e i n i t i a l in je c tio n .
F ra c tio n o n e w a s sh o w n b y g a s c h ro m a to g ra p h y to
c o n ta in o n ly th e re m a in in g s o lv e n t .
F ra c tio n tw o w a s c o lle c te d a s a
w h ite s o lid w ith a m e ltin g p o in t o f 6 7 - 6 8 ° C . A c o m p a ris o n o f th e n u c le a r
m a g n e tic r e s o n a n c e s p e c tru m (F ig u re 5 ), m e ltin g p o in t, a n d a g a s c h ro ­
m atogram w ith a n a u th e n tic sa m p le o f e x o tra n s e x o p ro v e d th is fr a c tio n
•V
I
JMI
ivvhV>
'
•
‘4
>
•
I
I
I
•
6 (ppm)
F ig . 5 . H1 m a g n e tic r e s o n a n c e s p e c tr a (60 M e.) o f n o rb o rn a d ie n e d im e rs:
to p , ex o tr a n s e x o ; c e n t e r , ex o tr a n s e n d o ; b o tto m , e n d o tr a n s e n d o . (38)
30
w a s th e e x o tr a n s ex o d im e r (V). The th ird fr a c tio n w a s a n o i l . The
n u c le a r m a g e n tic r e s o n a n c e s p e c tru m o f th is s a m p le (F ig u re 5) co m p ared
w ith th e n u c le a r m a g n e tic re s o n a n c e s p e c tru m o f a know n sa m p le o f
h y d ro c a rb o n d im e r ex o tr a n s e n d o s h o w e d th is fr a c tio n w a s th e ex o tr a n s
en d o d im e r (VI). The fo u rth fr a c tio n w a s a ls o c o lle c te d a s a n o i l . A co m ­
p a r is o n o f th e n u c le a r m a g n e tic r e s o n a n c e sp e c tru m (F ig u re 5) an d th e
g a s ch ro m a to g ra m
sh o w e d th is fr a c tio n w a s th e e n d o tr a n s e n d o d im er
(VII) w ith a v e ry s m a ll a m o u n t o f e x o tr a n s en d o d im e r. The fifth fr a c tio n
w a s found to c o n ta in th r e e c o m p o n e n ts . R e c h ro m a to g ra p h y o f th is f r a c ­
tio n on th e A utoprep u n d e r th e sam e c o n d itio n s a s b e fo re p e rm itte d th e
s e p a r a tio n o f th e th r e e c o m p o n e n ts . The f ir s t an d m a jo r c o m p o n e n t o f th e
fifth fr a c tio n w a s c o lle c te d a s a w h ite s o l i d . The n u c le a r m a g n e tic
r e s o n a n c e s p e c tru m (F ig u re 6) w a s c o m p a re d to th e n u c le a r m a g n e tic
r e s o n a n c e s p e c tru m o f th e c a g e co m p o u n d (IX) p ro p o s e d b y K atz and
A cton (44) a n d fo u n d to be i d e n t i c a l . A lth o u g h th e n u c le a r m a g n e tic r e s ­
o n a n c e s p e c tr a a re i d e n t i c a l , it is n e c e s s a r y to p o in t o u t t h a t th e o th e r
c a g e co m pound (X) w o u ld a ls o h a v e o n ly tw o p e a k s in a r a tio o f 3:1 in
6 (ppm)
F ig . 6.
m a g n e tic r e s o n a n c e s p e c tru m (100 M e .) o f n o rb o rn a d ie n e
c a g e d im e r.
31
th e sa m e re g io n o f th e n u c le a r m a g n e tic re s o n a n c e s p e c tru m (40, 41).
S in c e th is i s s o , i t m ay n o t be p o s s ib le to d is tin g u is h b e tw e e n th e tw o
c a g e co m p o u n d s b y th e n u c le a r m a g n e tic re s o n a n c e sp e c tru m , a l o n e .
T hus th e a s s ig n m e n t o f th e c a g e co m p o u n d in c o m p o n e n t o n e o f fr a c tio n
fiv e to s tr u c tu r e IX is o n ly t e n t a t i v e .
The s e c o n d c o m p o n e n t o f th e fifth fr a c tio n w a s a p o ly m e r (5 0 ).
T h is c o m p o u n d , i s o l a t e d in la r g e y ie ld in a l a t e r r e a c tio n d e s c r ib e d in
th e e x p e r im e n ta l s e c t i o n , w a s sh o w n to b e s ta b le to g r e a te r th a n 3 0 0 ° C .
I t w a s a s s ig n e d to b e a c a r b o n y l-c o n ta in in g p o ly m e r b e c a u s e th e in fra re d
s p e c tru m c o n ta in e d a 1715 cm ^ p e a k n o t o b s e r v e d in th e h y d ro c a rb o n
d im e r. The m a s s s p e c tru m sh o w e d p e a k s to a m o le c u la r w e ig h t o f o v e r
1 0 0 0 . The th ir d c o m p o n e n t o f th e fifth f r a c tio n w a s s u c h a m in o r p ro d u c t
i t w a s n o t in v e s t ig a te d fu r th e r .
~~-
I n te g r a tio n o f th e p e a k s o f th e g a s c h ro m a to g ra m s "led to th e p ro ­
d u c t p e r c e n ta g e s l i s t e d in T a b le V. I t is a s s u m e d fo r t h e s e c a lc u la tio n s
t h a t th e th r e e d im e rs a n d th e s in g le c a g e co m pound r e p r e s e n te d th e to ta l
r e a c tio n p ro d u c t. T h is a s s u m p tio n w a s n e c e s s a r y s in c e i t w a s e v id e n t
from th e c o m p a ris o n o f th e g a s ch ro m a to g ra m o f th e to ta l r e a c tio n p ro ­
d u c ts a n d o f th e f ilte r e d sa m p le th a t m o s t o f th e c a r b o n y l- c o n ta in in g
p o ly m e r w a s re m o v e d from th e s a m p le d u rin g th e f iltr a tio n th ro u g h a c t i ­
v a te d a lu m in a . The f iltr a tio n w h ic h w a s u s e d to rem o v e th e s o lid p a r ­
t i c l e s a n d th e c a rb o n y l c o m p o u n d s w a s a c c o m p lis h e d b y filte r in g th e
t o t a l r e a c tio n s a m p le th ro u g h a B u ch n er fu n n e l fille d , w ith a c tiv a te d
32 .
T a b le V
P ro d u c t R a tio s o f N o rb o rn a d ie n e D im ers
Exo tr a n s
exo
Exo tra n s
en d o
Endo tr a n s
endo
C ag e
Cr(CO)G
36
21
29
14
- sX - I - C r ( C o ) 4
52
20
23
5
Cr(CO) g
36
24
33
7
22
22
7
26
26
9
C r(C O )S
Cr(CO),
39
a lu m in a . The h y d ro c a rb o n d im e rs w e re e lu te d o ff th e a lu m in a w ith
■h e x a n e ; som e p o ly m e r w a s a ls o e lu te d b y th e h e x a n e .
33
T h e s e p e r c e n ta g e s a re b a s e d o n o n e s e r ie s o f r e a c tio n s w h ic h w e re
run a n d tr e a te d a s id e n t i c a l l y a s p o s s i b l e . The r e la tiv e v a lu e s b a s e d o n ■
th e in te g r a tio n a re c o n s i s t e n t w ith th e r e la tiv e v a lu e s b a s e d on th e p e a k
h e ig h t o f th e g a s ch ro m a to g ra m ta k e n o f th e to ta l r e a c tio n p ro d u c t.
The v a r ia tio n s in p e r c e n ta g e s a re la r g e r th a n e x p e c te d from s u b s e ­
q u e n t e x p e rim e n ta l r e s u lts d i s c u s s e d l a t e r in th is t h e s i s .
Some o f th e
v a r ia tio n s m ay be d u e to th e c h ro m a to g ra p h ic s e p a r a tio n . In th e c a s e o f
n o rb o rn a d ie n e chrom ium t e tr a c a r b o n y l, w ith tw o id e n tic a l s a m p le s th e re
is a m axim um v a r ia tio n in th e p e r c e n ta g e v a lu e s o f fiv e p e r c e n t in th e
v a lu e for ex o tr a n s e x o .
A n o th er e rro r is p o s s i b l e .
S in c e th e c a g e co m p o u n d is form ed in
s u c h s m a ll a m o u n ts , i t s p e a k on th e g a s c h ro m ato g ram i s o n ly s lig h tly
a b o v e th e b a s e lin e a n d th e re fo re th e s ta r tin g an d f in a l p o in ts o f th e i n ­
te g r a tio n m u s t be e s ti m a te d . In a d d itio n , a c o rre c tio n fo r th e am o u n t o f
c a rb o n y l p o ly m e r m u s t be e s tim a te d .
The f i r s t o b s e r v a tio n b a s e d o n t h e s e e x p e rim e n ta l r e s u lts is th a t
th e c a rb o n y l group m ay h a v e to be p r e s e n t s in c e d ic u m e n e chrom ium d o e s
n o t a c t a s a p h o to c h e m ic a l to g iv e a n y d im e r h y d ro c a rb o n p r o d u c ts .
In a l l c a s e s (e x c e p t d ic u m e n e chrom ium ) id e n tic a l p ro d u c ts a re
form ed a n d s im ila r p e r c e n ta g e s a re o b ta in e d . The f a c t t h a t th e p ro d u c ts
a re id e n tic a l is in te r p r e te d to m ean th a t a ll th e h y d ro c a rb o n d im ers a re
co m in g from a n in te rm e d ia te w h ic h c o n ta in s th e sam e n u m b er o f c a rb o n y l
g r o u p s . I t h a s b e e n sh o w n (45, 51) t h a t th e h y d ro c a rb o n d im e r p ro d u c ts o f
n o rb o rn a d ie n e v a ry w ith th e num b er o f r e p la c e a b le c a rb o n y l g r o u p s .
34
A n o th er c o n c lu s io n d raw n from T a b le V is th a t th e s t e r i c fa c to rs o f
th e o rg a n ic lig a n d s b e n z e n e , to lu e n e -a n d m e s ity le n e do n o t a f f e c t th e
n u m b e r o f fin a l p ro d u c ts o r a f f e c t g r e a tly th e p ro d u c t p e r c e n t a g e s . In
a d d itio n , c o m p arin g chrom ium h e x a c a rb o n y l w ith b e n z e n e o r m e s ity le n e
chrom ium tr ic a rb o n y l in d ic a te s th a t th e s t e r i c e f f e c ts o f th e o rg a n ic
lig a n d c o m p ared to a c a rb o n y l d o e s n o t a f f e c t th e fin a l p ro d u c ts o r a f f e c t
g r e a tly th e p ro d u c t p e r c e n t a g e s . S in c e th e s t e r i c d if f e r e n c e b e tw e e n
c a r b o n y l, b e n z e n e , to lu e n e an d m e s ity le n e a re l a r g e , o n e m ig h t e x p e c t
th e r e to be a la rg e v a r ia tio n in th e n a tu re o f th e p ro d u c ts if th e o rg a n ic
lig a n d w a s p r e s e n t w h en th e a c tu a l d im e riz a tio n o c c u rre d on th e m e ta l,
a s i s b e lie v e d to o c c u r . S in c e th e re i s no v a r ia tio n in th e ty p e o f p ro ­
d u c t s , th e in d ic a tio n is th a t b e n z e n e , to lu e n e a n d m e s ity le n e a re l o s t
p rio r to th e a c tu a l fo rm a tio n o f a ll th e h y d ro c a rb o n d im e r s . It w ill be
p ro p o s e d t h a t th e c a g e d im e r is n o t fo rm ed from th e d im e riz a tio n o f
n o rb o rn a d ie n e a tta c h e d d ir e c tly to th e c h ro m iu m , b u t r a th e r th a t an
in te rm e d ia te s im ila r to d im e r XI is fo rm ed w h ic h th e n r e a c ts to form th e
c a g e c o m p o u n d . T his sa m e d im e r is p ro p o s e d b y K atz an d A cton (44) to
g iv e th e c a g e com pound b y th e r e a c tio n w ith h y d ro io d ic a c id .
I s o la tio n o f In te rm e d ia te s U sin g C hrom ium H e x a c a rb o n y l
A 0 .0 1 4 3 M chrom ium h e x a c a rb o n y l s o lu tio n in n o rb o rn a d ie n e w a s
p u t in to th e p h o to r e a c to r an d p u rifie d n itro g e n w as b u b b le d th ro u g h th e
s o lu tio n fo r 12 h o u r s . An in fra re d s p e c tru m o f th e s o lu tio n w a s ta k e n a n d
th e ir r a d ia tio n , u s in g a p y re x f i l t e r , w a s s t a r t e d . In fra re d s p e c tr a w ere
ta k e n a t h a lf - h o u r in te r v a ls for s e v e n h o u r s . A fter a t o t a l ir r a d ia tio n
35
tim e o f te n h o u rs a n o th e r in fra re d s p e c tru m w a s ta k e n a n d c o m p ared to
th e o n e ta k e n a t s e v e n h o u r s . The c o m p a riso n sh o w e d no fu rth e r c h a n g e
h a d o c c u rre d s o th e ir r a d ia tio n w a s s to p p e d .
In fra re d s p e c tr a a n d g a s c h ro m a to g ra m s ta k e n d u rin g th e c o u rs e o f
th e r e a c tio n s in d ic a te d t h a t th e chrom ium h e x a c a rb o n y l w a s c h a n g e d
r a p id ly to a s e c o n d m e ta l c a r b o n y l. S e c o n d ly , th e h y d ro c a rb o n d im er
p ro d u c ts d id n o t a p p e a r in th e g a s c h ro m a to g ra m s .u n til a f te r th e a p p e a r ­
a n c e o f th e s e c o n d m e ta l c a rb o n y l a n d s to p p e d in c r e a s in g in am o u n t w h en
th e s e c o n d m e ta l c a rb o n y l p e a k w a s no lo n g e r p r e s e n t in th e in fra re d
s p e c tr a (F ig u re 2 7 ). The in fra re d s p e c tr a an d g a s c h ro m a to g ra m s in d i­
c a te d fu rth e r t h a t th e s e c o n d m e ta l c a rb o n y l w a s id e n t i c a l to
n o rb o rn a d ie n e chrom ium t e tr a c a r b o n y l.
A n o th er s o lu tio n , s im ila r in c o m p o s itio n , w a s p re p a re d and
ir r a d ia te d a s d e s c r ib e d a b o v e . A fter tw o h o u rs o f ir r a d ia tio n , th e
c a rb o n y l b a n d o f chrom ium h e x a c a rb o n y l h a d d is a p p e a r e d c o m p le te ly from
th e in fra re d s p e c tru m , a n d th e in fra re d b a n d s o f th e s e c o n d m e ta l c a r ­
b o n y l w e re s t i l l e v id e n t (F ig u re s 7, 8 ). The ir r a d ia tio n w a s c o n tin u e d a n d
th e in fra re d s p e c tru m s h o w e d t h a t a l l th e m e ta l c a rb o n y l w a s a b s e n t a f te r
s ix h o u rs (F ig u re 9 ).
1
A n o th er s o lu tio n w a s ir r a d ia te d fo r tw o h o u r s . T he ir r a d ia tio n w a s
s to p p e d a n d th e r e a c tio n m ix tu re w a s a llo w e d to s ta n d u n d e r n itro g e n fo r
19 h o u rs w ith in fra re d s p e c tr a ta k e n a t 2 - h o u r i n t e r v a l s . A p e a k a t
1988 cm "*■in th e in fra re d s p e c tru m a p p e a re d (chrom ium h e x a c a rb o n y l,
1988 cm *) a f te r ir r a d ia tio n w a s s to p p e d fo r s ix h o u rs a n d g re w to a
WAVENUMBER CM- '
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'?ig . 7.
0 tim e o f ir r a d ia tio n fo r chrom ium h e x a c a rb o n y l.
WAVENUMBER CM
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F ig . 8.
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2 h o u r s o f ir r a d ia tio n for chrom ium h e x a c a r b o n y l.
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F ig . 9 .
6 h o u rs o f ir r a d ia tio n fo r chrom ium h e x a c a r b o n y l.
CO
38
m axim um h e ig h t o f o n e - h a l f i t s o r ig in a l in t e n s i t y a n d th e in fra re d p e a k s
d u e to th e s e c o n d m e ta l c a rb o n y l re m a in e d u n c h a n g e d (F ig u re 10).
The r e a p p e a r a n c e o f th e chrom ium h e x a c a rb o n y l in fr a r e d b an d m ay
be d u e to th e re fo rm a tio n o f chrom ium h e x a c a rb o n y l from chrom ium
p e n ta c a rb o n y l an d from n o rb o rn a d ie n e chrom ium p e n ta c a rb o n y l w h ic h
c o u ld lo s e th e n o rb o rn a d ie n e to form chrom ium p e n ta c a r b o n y l. It h a s
b e e n re p o rte d (60) t h a t chrom ium h e x a c a rb o n y l w h en ir r a d ia te d w ith u l t r a ­
v i o l e t lig h t form s chrom ium p e n ta c a rb o n y l w h ic h is a l s o p ro p o s e d to be
a n in te rm e d ia te in th e fo rm a tio n o f chrom ium h e x a c a rb o n y l d e r iv a tiv e s
form ed th ro u g h th e r e p la c e m e n t o f o n e o r m ore c a rb o n y l g ro u p s by lig a n d s
s u c h a s n itr id e s a n d o l e f i n s . In th e sa m e p a p e r (60) i t w a s a ls o re p o rte d
t h a t w h e n th e ir r a d ia tio n w a s s to p p e d th e chrom ium p e n ta c a rb o n y l r e ­
v e r te d s u b s t a n t i a l l y b a c k to chrom ium h e x a c a r b o n y l. In te rfe rin g p e a k s
from th e n o rb o rn a d ie n e a n d s e c o n d m e ta l c a rb o n y l d id n o t a llo w th e
chrom ium p e n ta c a rb o n y l p e a k to b e id e n tif ie d .
To c h e c k th e s t a b i l i t y o f th e s e c o n d in te rm e d ia te m e ta l c a rb o n y l
fu r th e r , a s o lu tio n o f chrom ium h e x a c a rb o n y l an d n o rb o rn a d ie n e w a s
h e a te d to 7 0 °C fo r fiv e h o u rs w ith o u t a n y c h a n g e s o b s e r v e d in th e in f r a ­
re d s p e c tru m o f e ith e r chrom ium h e x a c a rb o n y l or th e s e c o n d m e ta l c a r ­
b o n y l. T h is s o lu tio n w a s c o o le d to room te m p e ra tu re a n d th e s o lu tio n
ir r a d ia te d fo r a n a d d itio n a l 30 m in u te s . The p e a k a t 1988 cm
in th e
in f r a r e d s p e c tru m a g a in d is a p p e a r e d . The r e a c tio n m ix tu re w a s rem o v ed
from th e r e a c tio n v e s s e l a n d th e s o lv e n t q u ic k ly e v a p o r a te d in a ro to
e v a p o r a to r to a v o lu m e o f 5 m l. T h is c o n c e n tr a te d s o lu tio n w as
WAVENUMBER CM*'
40 0 0 3000
2000
!5 0 0
1300
1100
!000
ICO
90
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IO
0
F ig . 10.
2 h o u rs o f ir r a d ia tio n a n d th e n 6 h o u rs in th e d a rk fo r chrom ium h e x a c a rb o n y l.
40
c h ro m a to g ra p h e d on a n a c ti v a te d s i l i c a g e l c o lu m n . H e x a n e w a s a d d e d to
rem o v e a n y h y d ro c a rb o n d im e rs an d u n til a b rig h t y e llo w b a n d s ta r te d to
b e e lu te d from th e c o lu m n . The h e x a n e fr a c tio n w a s e v a p o r a te d an d
sh o w n by in fra re d s p e c tru m n o t to c o n ta in a n y m e ta l c a r b o n y ls . B en zen e
w a s a d d e d to th e co lu m n a n d th e b rig h t y e llo w b a n d c o l l e c t e d . The
b e n z e n e w a s re m o v e d a n d th e re m a in in g y e llo w s o lid s u b lim e d . In fra re d
a n d n u c le a r m a g n e tic r e s o n a n c e s p e c tr a w e re ta k e n o f th is y e llo w m e ta l
c a rb o n y l ( m .p . 9 2 -9 3 ° C ) an d c o m p ared to th e in fra re d a n d n u c le a r m ag ­
n e tic r e s o n a n c e s p e c tr a o f a n a u th e n tic s a m p le o f n o rb o rn a d ie n e .
chrom ium te tr a c a r b o n y l. The s p e c tr a w e re id e n tic a l a n d th e m e ltin g p o in t
o f th e y e llo w s o lid w a s id e n tic a l to th a t re p o rte d fo r n o rb o rn a d ie n e
chrom ium te tr a c a r b o n y l.
In c o n c lu s io n , th is e x p e rim e n t s h o w e d t h a t chrom ium h e x a c a rb o n y l
c h a n g e d r a p id ly to a s e c o n d m e ta l c a r b o n y l, w h ic h w a s i s o l a t e d and
sh o w n to b e n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l. It w a s in d ic a te d b y
-I
th e re a p p e a r a n c e o f th e chrom ium h e x a c a rb o n y l in fra re d b a n d a t 19 88 cm
th a t a n in te rm e d ia te m e ta l c a r b o n y l, chrom ium p e n ta c a r b o n y l, w as
form ed d u rin g th e r e a c tio n s e q u e n c e o f chrom ium h e x a c a rb o n y l g o in g to
n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l. I t w a s a ls o fo u n d th a t th e h y d ro ­
c a rb o n d im e rs w e re n o t fo u n d u n til n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l
w a s p r e s e n t a n d th e d im e r s to p p e d b e in g form ed w h en n o rb o rn a d ie n e
chrom ium te tr a c a r b o n y l w a s a b s e n t.
B e c a u s e n o rb o rn a d ie n e chrom ium t e tr a c a r b o n y l, w h en u s e d a s th e
r e a c t a n t te m p la te , g iv e s th e sa m e p ro d u c ts a s th e o th e r r e a c ta n t
41
te m p la te s u s e d , a n d b e c a u s e fo rm a tio n o f d im e rs in th e chrom ium h e x a • c a rb o n y l a p p e a rs to d e p e n d upo n th e p r e s e n c e o f n o rb o rn a d ie n e chrom ium
te tr a c a r b o n y l i t w a s d e c id e d to c h e c k i f n o rb o rn a d ie n e chrom ium t e t r a c a rb o n y l w a s th e com m on in te rm e d ia te o f a l l th e r e a c tio n s in d ic a te d by
th e p ro d u c ts an d p e r c e n ta g e p ro d u c ts e x p e r im e n ts .
I s o l a t i o n o f In te rm e d ia te s fo r B e n z e n e , T o lu en e o r M e s ity le n e
C hrom ium T ric a rb o n y l
S o lu tio n s o f b e n z e n e , to lu e n e a n d m e s ity le n e chrom ium tric a rb o n y l
in n o r b o r n a d ie n e , 0 .0 1 4 3 M , w e re p re p a re d an d p u t in to th e p h o to
r e a c to r . N itro g e n w a s b u b b le d th ro u g h th e s o lu tio n s fo r 12 h o u r s . An
in fra re d s p e c tru m w a s th e n ta k e n j u s t b e fo re th e ir r a d ia tio n , w ith a p y re x
f i l t e r , w a s s ta r te d a n d a t h a lf - h o u r in te r v a ls for th re e h o u r s . A fin a l
in fra re d s p e c tru m w a s ta k e n a f te r fiv e a n d o n e - h a lf h o u rs o f to ta l ir r a d i­
a tio n tim e . The i n i t i a l y e llo w s o lu tio n tu rn e d re d im m e d ia te ly a f te r th e
ir r a d ia tio n w a s s t a r t e d .
From a c o m p a riso n o f th e in fra re d s p e c tr a in th e m e ta l c a rb o n y l
re g io n fo r th e b e n z e n e , to lu e n e an d m e s ity le n e chrom ium tric a rb o n y l
r e a c tio n s i t w a s c o n c lu d e d th a t th e re w e re th re e d if f e r e n t m e ta l c a rb o n y ls
p r e s e n t d u rin g th e c o u rs e o f th e .r e a c tio n s (F ig u re 2 8 ), a n d a ls o th a t th e
th r e e r e a c tio n s w e re u n d e rg o in g s im ila r c h a n g e s . The f i r s t m e ta l c a rb o n y l
w a s th e s ta r tin g m a t e r i a l , th e s e c o n d m e ta l c a rb o n y l w a s a re d co m p le x
a n d w a s fo u n d in s m a ll a m o u n ts im m e d ia te ly a f te r th e ir r a d ia tio n w as
s t a r t e d . The th ir d c o m p le x w a s n o t s e e n in th e in fra re d s p e c tru m u n til
th e s o lu tio n h ad b e e n ir r a d ia te d fo r a p p ro x im a te ly 30 m in u te s .
42
The m e s ity le n e chrom ium tric a rb o n y l r e a c tio n w a s re p e a te d to d e ­
te rm in e w h a t m e ta l c a rb o n y ls form ed a f te r th e ir r a d ia tio n w a s s t a r t e d .
The s o lu tio n w a s ir r a d ia te d fo r 30 m in u te s , a t w h ic h tim e th e p e a k in th e
in fra re d s p e c tru m d u e to m e s ity le n e chrom ium tric a rb o n y l h a d v a n is h e d
b u t th e s e c o n d m e ta l c a rb o n y l c o m p le x , th e re d c o m p le x , in fra re d b a n d s
w e re p r e s e n t (F ig u re s 11, 12). The ir r a d ia tio n w a s c o n tin u e d an d th e
p e a k s o f a th ird m e ta l c a rb o n y l a p p e a re d (F ig u re 13). The ir r a d ia tio n w a s
c o n tin u e d a n d a f te r a to ta l o f th re e a n d o n e - h a lf h o u rs o f ir r a d ia tio n th e
m e ta l c a rb o n y l b a n d s w e re a b s e n t (F ig u re 14).
A nother- s im ila r s o lu tio n w a s ir r a d ia te d , a s b e fo re fo r 30 m in u te s .
The ir r a d ia tio n w a s s to p p e d an d h a lf th e s o lu tio n w a s a llo w e d to s ta n d in
th e d a rk fo r 24 h o u r s . An in fra re d s p e c tru m w a s ta k e n a f te r s ix h o u rs a n d
th e s p e c tru m sh o w e d t h a t th e p e a k s d u e to m e s ity le n e chrom ium t r i c a r ­
b o n y l h a d re a p p e a re d a n d th e in fra re d b a n d s due to th e re d c o m p le x h ad
d e c r e a s e d in i n te n s ity (F ig u re 15). An in fra re d s p e c tru m w a s a ls o ta k e n
a f te r 24 h o u r s , an d c o m p a riso n w ith th e o n e ta k e n a t s ix h o u rs (F ig u re 15)
sh o w e d no fu rth e r c h a n g e h a d o c c u r r e d . The s e c o n d h a lf o f th e r e a c tio n
m ix tu re w a s rem o v ed from th e r e a c tio n v e s s e l an d ta k e n r a p id ly to d ry ­
n e s s in a ro to e v a p o r a to r . The w a te r b a th fo r th e ro to e v a p o r a to r w a s
-
k e p t a t room te m p e r a tu r e . The r e s id u e a f te r th e s o lv e n t w a s rem o v ed w a s
a r e d - y e llo w s o lid . The r e d - y e llo w s o lid w a s p u t in to a s u b lim a to r im ­
m e d ia te ly a n d h e a te d to 3 5 ° C . A y e llo w s o lid w a s c o lle c te d on th e
s u b lim a to r c o ld fin g e r a n d th e red s o lid m a te ria l re m a in e d b e h in d . The
re d s o lid w a s h e a te d to 7 0 °C in th e s u b lim a to r b u t i t re m a in e d in th e
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F ig . 11.
0 tim e o f ir r a d ia tio n fo r m e s ity le n e chrom ium tric a rb o n y l
WAVENUMBER CM'1
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F ig . 1 2 .
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30 m in u t e s o f ir r a d ia t io n fo r m e s i t y l e n e ch rom iu m tr ic a r b o n y l
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F ig . 13.
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I h o u r o f ir r a d ia tio n fo r m e s ity le n e chrom ium tr i c a r b o n y l.
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F ig . 14 .
3 V2 h o u r s o f ir r a d ia tio n for m e s i t y l e n e ch rom iu m t r ic a r b o n y l.
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F ig . 15. 30 m in u te s o f ir r a d ia tio n an d th e n 6 h o u rs in th e d a rk fo r m e s ity le n e chrom ium
tr i c a r b o n y l.
46
b o tto m u n c h a n g e d . An in fr a r e d s p e c tru m , a m a s s s p e c tru m (F ig u re 16)
a n d a n u c le a r m a g n e tic r e s o n a n c e s p e c tru m w e re ta k e n o f th e s u b lim e d
y e llo w s o lid m a te ria l a n d a ll w e re id e n t i c a l to th e c o rre s p o n d in g s p e c tr a
o f a n a u th e n tic s a m p le o f n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l. The
in fr a r e d s p e c tru m a l s o w a s id e n tic a l to th e in fra re d s p e c tru m o f th e th ird
m e ta l c o m p le x fo u n d in th e r e a c tio n m ix tu re .
The re d c o m p le x (th e r e s id u e from th e su b lim a to r) w a s v e ry u n ­
s ta b l e a n d d e c o m p o s e d in th e a i r a n d in s o lv e n ts (s u c h a s h e x a n e ,
p e tro le u m e th e r , c a rb o n t e t r a c h l o r i d e , c h lo ro fo rm ,
N , N -d im e th y lfo rm a m id e , d im e th y l s u lf o x id e , b e n z e n e , e th a n o l an d
m e th a n o l) e v e n w h en th e a ir w a s r e p la c e d b y d e o x y g e n a te d n itr o g e n . An
in fr a r e d s p e c tru m o f th e re d s o lid w a s ta k e n u s in g p o ta s s iu m bro m id e
(F ig u re 17) a n d th is s h o w e d th e re d m a te r ia l w a s a m e ta l c a rb o n y l co m ­
p le x a n d id e n tic a l to th e s e c o n d m e ta l c a rb o n y l c o m p le x , th e re d co m ­
p le x , in th e r e a c tio n o f m e s ity le n e chrom ium tric a rb o n y l.. B e c a u se o f i t s
i n s t a b i l i t y in s o l v e n t s , a n u c le a r m a g n e tic r e s o n a n c e s p e c tru m w a s n o t
p o s s i b l e so a m a s s s p e c tru m w a s ta k e n (F ig u re 18). The m a s s sp e c tru m
h a d a p a r e n t p e a k o f 348 a to m ic m a s s u n i t s , w h ic h is c o r r e c t fo r a co m ­
p le x c o n ta in in g m e s i ty le n e , n o rb o rn a d ie n e a n d th re e c a r b o n y ls .
The n e x t m a jo r p e a k b e lo w 3 48 i s 2 5 6 , w h ic h c a n b e a s s ig n e d to
e ith e r n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l o r m e s ity le n e chrom ium
t r i c a r b o n y l. The m a s s s p e c tru m o f th e re d c o m p le x d o e s n o t.h a v e a s i g ­
n if ic a n t p e a k a t 2 2 8 , in c o n tr a s t to th e m a s s s p e c tru m o f n o rb o rn a d ie n e
chrom ium te tr a c a r b o n y l. The m a s s s p e c tru m o f th e re d c o m p le x h a s la rg e
F ig . 16.
M a s s s p e c tru m o f n o rb o rn a d ie n e chrom ium t e t r a c a rb o n y l.
WAVENUMBER CM’1
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co
F ig . 17.
In fra re d sp e c tru m o f re d c o m p le x .
100
90
8070*
w 60+j
_c
Cn
CD
X 50'
CO
CD
a. 404
3020^
F ig . 18.
M a s s s p e c tru m o f re d c o m p le x .
50
p e a k s a t 1 0 5 , 119, 1 7 1 , 172 (T ab le VI) w h ic h a re n o t p r e s e n t a s la rg e
p e a k s in th e m a s s s p e c tru m o f n o rb o r n a d ie n e . T hus th e 2 56 p e a k is
a s s ig n e d to m e s ity le n e chrom ium tr i c a r b o n y l. A fin a l p o in t a b o u t th e
m a s s s p e c tru m o f th e re d c o m p le x i s d e m o n s tra te d in th e p e a k s w h ic h
c o n ta in a m e s ity le n e g r o u p . From th e p e a k h e ig h t i t is e v id e n t .th a t th e
T a b le VI
P e a k A s s ig n m e n ts fo r th e M a s s S p ectru m o f th e Red C o m p lex
CrCO
199
( - 4 4 - Gr(CO)Z
280
" A
s
255
O
2^6
C r(CO),
51
la r g e r p e a k s c o n ta in a m e s ity le n e w h ic h h a s l o s t o n e h y d ro g e n and
fo rm ed p o s s i b l y a d im e th y l tro p y liu m io n . T h is w o u ld c o rre s p o n d to th e
b e n z y l io n lo s in g a h y d ro g e n to form th e tro p y liu m io n , w h ic h i t d o e s b e ­
c a u s e o f in c r e a s e d r e s o n a n c e s t a b i l i t y o f th e to p y liu m io n a s co m p ared
to th e b e n z y l io n . To c h e c k th e th e rm a l s t a b i l i t y o f th e re d c o m p le x a
r e a c tio n w a s run a n d th e re d c o m p le x i s o l a t e d , k e e p in g th e te m p e ra tu re
b e lo w 3 5 ° C . M a s s s p e c tr a w ere th e n ta k e n o f th e s a m p le a t 2 0 o C , 2 5 0 C ,
5 0 ° C , 7 0 ° C , 9 0 ° C , 1 1 5 °C , a n d th e re d c o m p le x sh o w e d no th e rm a l d e ­
c o m p o s itio n .
Both b e n z e n e a n d to lu e n e chrom ium tric a rb o n y l a l s o form ed a red
c o m p le x a n d h a d in fra re d s p e c tr a c h a n g e s s im ila r to th e m e s ity le n e
chrom ium tric a rb o n y l r e a c tio n (F ig u re s 19-2 6 ).
The in fra re d s p e c tr a o f th e b e n z e n e , to lu e n e a n d m e s ity le n e
chrom ium tric a rb o n y l r e a c tio n s d e m o n s tra te s th e p r e s e n c e o f n o rb o rn a d ie n e chrom ium t e t r a c a rb o n y l in a ll c a s e s . In a d d itio n , th e f a c t th a t th e
m e s ity le n e chrom ium tric a rb o n y l in fra re d b a n d s a re c o m p le te ly g o n e in
30 m in u te s b u t r e a p p e a r u p o n s ta n d in g in th e d a rk in d ic a te s th e re m u st b e
a n in te rm e d ia te found on th e p a th o f th e r e a c tio n o f th e m e s ity le n e
chrom ium tr ic a rb o n y l g o in g to n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l.
T h is i s so s in c e n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l w ill n o t re v e rt
b a c k to m e s ity le n e chrom ium tric a rb o n y l in th e p r e s e n c e o f th e
m e s i ty le n e , a s i s in d ic a te d by. th e c o n s ta n t in te n s ity o f th e in fra re d b a n d
d u e to n o rb o rn a d ie n e chrom ium te tr a c a r b o n y l w h en m e s ity le n e is p r e s e n t.
T he in te rm e d ia te th a t r e v e r ts b a c k to th e s ta r tin g m a te ria l i s p ro p o s e d to
WAVENUMBER CM"1
4000 3000
2000
1500
1300
1100
1000
300
800
700
650
100
90
80
70
60
50
40
30
20
10
0
WAVENUMBER CM"1
Cn
N)
4 0 0 0 3000
F ig . 2 0 .
2000
1500
1300
1100
1000
900
800
30 m in u t e s o f ir r a d ia tio n fo r b e n z e n e ch rom iu m t r ic a r b o n y l
700
650
WAVENUMBER CM*1
4000 3000
F ig . 21.
2000
1500
1300
1100
1000
900
800
700
650
800
700
650
I h o u r o f ir r a d ia tio n fo r b e n z e n e chrom ium tr i c a r b o n y l.
WAVENUMBER CM'1
4 0 0 0 3000
2000
1500
1300
1100
1000
SOO
100
90
80
70
60
50
40
30
20
10
0
F ig . 2 2 .
3 V2 h o u r s o f ir r a d ia tio n fo r b e n z e n e ch rom iu m t r ic a r b o n y l.
WAVENUMBER CM"'
4000 3000
2000
1500
1300
1100
1000
SOO
SCO
700
650
!CO
SO
GO
70
GO
50
40
50
20
!0
O
F ig . 23
0 tim e o f ir r a d ia tio n fo r to lu e n e chrom ium tric a rb o n y l
WAVENUMBER CM'
4 0 0 0 3000
2000
1500
1500
IIOO
IOOO
900
800
700
650
IOO
SO
SO
70
60
50
40
30
20
IO
O
F ig . 2 4 .
30 m in u te s o f ir r a d ia tio n for t o lu e n e ch rom iu m t r ic a r b o n y l.
WAVENUMBER CM"1
4000 3000
F ig . 2 5 .
2000
1500
1300
1100
1000
900
800
700
650
100
90
SO
70
60
50
40
30
20
10
0
I h o u r o f ir r a d ia tio n fo r to lu e n e chrom ium tric a rb o n y l
WAVENUMBER CM
4 0 0 0 3000
F ig . 2 6 .
2000
1500
1300
1100
!000
Cn
Cn
900
800
31/2 h o u r s o f ir r a d ia t io n for t o lu e n e ch rom iu m t r ic a r b o n y l.
700
650
ICO
90
80
70
60
50
40
30
20
IO
0
56
b e th e re d c o m p le x . The in t e r m e d i a t e c o n t a i n s e i t h e r b e n z e n e , to lu e n e
o r m e s i t y l e n e a n d n o rb o r n a d ie n e chrom ium t r i c a r b o n y l .
O th e r I n v e s t i g a t i o n s
In th e c a s e o f th e chrom ium r e a c t i o n w ith n o r b o r n a d ie n e , th e l a s t
t r a c e s o f n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l a re n o t g o n e from th e
i n f r a r e d s p e c tru m u n til a t o t a l r e a c t i o n tim e o f s i x h o u r s , In th e c a s e o f
b e n z e n e , t o l u e n e o r m e s i t y l e n e , th e l a s t i n d i c a t i o n s o f n o r b o r n a d ie n e
chrom ium t e t r a c a r b o n y l a r e g o n e in th r e e a n d o n e - h a l f h o u r s . T aken by
i t s e l f t h i s w o u ld i n d i c a t e t h a t chrom ium h e x a c a r b o n y l r e a c t s s lo w e r th a n
b e n z e n e , to l u e n e o r m e s i t y l e n e chrom ium t r i carbonyl.. H o w e v e r, e a c h
chrom ium h e x a c a r b o n y l c a n form o n e n o r b o r n a d ie n e chrom ium t e t r a c a r ­
b o n y l , b u t t h i s o n e - t o - o n e ra tio i s n o t p o s s i b l e for th e b e n z e n e , to lu e n e
a n d m e s i t y l e n e chrom ium tr i c a r b o n y l s i n c e t h e y m u s t g a in a c a rb o n y l
w h ic h m u s t co m e from th e d e c o m p o s itio n o f th e s t a r t i n g m a t e r i a l . Thus
th e r e i s l e s s chrom ium t e t r a c a r b o n y l form ed in th e a r e n e chrom ium
tr i c a r b o n y l s i f e q u a l m o la r s o l u t i o n s a r e u s e d in e a c h c a s e a s th e y w e re
in t h e s e e x p e r i m e n t s . To c h e c k th e tim e s o f th e r e a c t i o n s more c a r e f u l ly
a tim e s tu d y w a s c a r r i e d o u t.
For th e tim e s tu d y t h e p ro c e d u re w a s to m ak e a 7 0 - m l s o lu tio n o f
t h e m e ta l c a r b o n y l in n o r b o r n a d i e n e . N itr o g e n w a s b u b b le d th ro u g h th e
s o l u t i o n fo r 12 h o u rs a n d t h e s a m p le i r r a d i a t e d u s in g a c o r e x f ilte r .. A
s a m p le w a s re m o v e d j u s t b e fo re th e i r r a d i a t i o n w a s s t a r t e d a n d a t o n e h o u r i n t e r v a l s t h e r e a f t e r u n til no c h a n g e a p p e a r e d to h e o c c u r r in g by th e
57
g a s c h ro m a to g r a p h ic a n a l y s i s , a f te r w h ic h tim e s a m p l e s w e re re m o v e d a t
lo n g e r i n t e r v a l s .
A p lo t s h o w in g th e tim e v e r s u s h y d ro c a rb o n d im e r p r o d u c ts found
a s d e te r m in e d s o l e l y b y p e a k h e ig h t i n d i c a t e s th e m e s i t y l e n e chromium
tr i c a r b o n y l d o e s r e a c t f a s t e r th a n chrom ium h e x a c a r b o n y l (F ig u re s 2 7, 2 8).
E q u a lly a s im p o r ta n t, th e d a ta i n d i c a t e a n in d u c tio n p e r i o d , a n d th u s
s u g g e s t t h a t th e a c t u a l r e a c t a n t t e m p la te fo r th e d im e r iz a tio n is form ed
a f t e r th e s a m p le h a s b e e n i r r a d i a t e d . The i d e a . o f a n in d u c tio n p e rio d i s
s u p p o r te d b y th e B e e r's Law a n d in f r a r e d s p e c t r a s t u d i e s d e s c r i b e d
b e lo w .
In t h e B e e r's Law e x p e r im e n t th e u l t r a v i o l e t s p e c tru m o f chromium
h e x a c a r b o n y l in a 1:100 s o lu tio n o f n o r b o m a d ie n e a n d c y c lo h e x a n e w a s
c o m p a re d w ith th e u l t r a v i o l e t s p e c tru m o f a s a t u r a t e d s o l u t i o n of
chrom ium h e x a c a r b o n y l in h e x a n e . The o b j e c t w a s to s e e i f th ere, w e re
a n y c h a n g e s in th e a b s o r p tio n s p e c tru m o f chrom ium h e x a c a r b o n y l t h a t
w o u ld i n d i c a t e th e r e w a s a b o n d b e tw e e n th e chrom ium h e x a c a r b o n y l a n d
th e n o r b o m a d i e n e p rio r to i r r a d i a t i o n . From c o m p a r is o n o f th e u l t r a v i o l e t
s p e c t r a , i t w a s c o n c lu d e d t h a t n o r b o m a d ie n e and chrom ium h e x a c a r b o n y l
e i t h e r d id n o t form a g ro u n d s t a t e c o m p le x or formed a c o m p le x in v e ry
lo w c o n c e n t r a t i o n .
A n o th e r e x p e r im e n t u s e d to s h o w ,there w a s n o g ro u n d s t a t e c o m ­
p l e x w a s a n in f r a r e d s p e c tru m s t u d y . In t h i s s tu d y tw o s o l u t i o n s of
n o r b o m a d i e n e a n d chrom ium h e x a c a r b o n y l w e re c o m p a re d to th e in fr a r e d
s p e c tr u m o f chrom ium h e x a c a r b o n y l in c a r b o n te t r a c h l o r i d e a n d an
58
CD
100
80
H*
t
0
H)
CO
9
1DJ
f t
O
CTQ
10 S
Time (h o u rs )
F ig . 27. P lo t o f p e a k h e ig h ts o f p r o d u c ts v e r s u s tim e a n d p lo t of in fr a r e d
b a n d s i n t e n s i t y o f th e m e ta l c a r b o n y ls v e r s u s tim e: I) chrom ium
h e x a c a r b o n y l , II) n o r b o r n a d ie n e chrom ium t e t r a c a r b o n y l , III) e x o tr a n s
e x o d im e r , IV) e n d o t r a n s e n d o d im e r, V) e x o tr a n s e n d o d im e r, VI) c a g e
d im e r.
>tj
CD
F ig . 2 8 . Plo t o f p e a k
b a n d s i n t e n s i t y o f th e
chrom ium t r i c a r b o n y l ,
t e t r a c a r b o n y l , IV) e x o
VII) c a g e d im e r.
h e i g h t s o f p r o d u c ts v e r s u s tim e a n d p lo t o f in fra re d
m e ta l c a r b o n y ls v e r s u s tim e: I) m e s i ty le n e
II) re d c o m p le x , III) n o rb o r n a d ie n e chromium
tr a n s e x o , V) e n d o tr a n s e n d o , VI) e x o tr a n s e n d o ,
59
in f r a r e d s p e c tru m o f p u re n o r b o r n a d i e n e . The r e a s o n for th e c o m p a ris o n
w a s to s e e i f th e r e w a s a n y s h i f t o f th e chrom ium h e x a c a r b o n y l bond due
to b o n d in g w ith n o r b o r n a d ie n e . A c o m p a r is o n s h o w e d no s h i f t a n d i t w a s
c o n c lu d e d t h a t th e r e w a s no b o n d in g b e t w e e n n o r b o r n a d ie n e a n d
chro m iu m h e x a c a r b o n y l in th e g ro u n d s t a t e o r i f th e r e w a s a n y i t w a s in
v e r y lo w c o n c e n t r a t i o n s .
F u rth e rm o re , to e x a m in e th e th e r m a l r e a c t i o n a s o l u t i o n o f n o rb o rn ­
a d i e n e a n d chrom ium h e x a c a r b o n y l w a s h e a t e d to v a r io u s te m p e r a t u r e s
( 5 7 ° C , 8 3 ° C , 8 9 °C ) for. 24 h o u rs a t e a c h te m p e r a t u r e . The s o l u t i o n s w e re
a n a l y z e d b y g a s c h ro m a to g ra p h y a t 2 4 - h o u r i n t e r v a l s to s e e i f th e r e w a s
a th e rm a l r e a c t i o n from a g ro u n d s t a t e c o m p le x . The g a s ch ro m ato g ram
d id n o t s h o w a n y d im e rs o v e r th e 3 - d a y p e r io d a n d th e in f r a r e d p e a k o f
-I
chrom ium h e x a c a r b o n y l a t 1988 cm
i n d i c a t e s a l l th e s t a r t i n g m a te r ia l
w as reco v ered .
A n o th e r p o i n t d e m o n s t r a t e d b y th e tim e s tu d y w a s th e n e c e s s i t y o f
th e p r e s e n c e o f a m e ta l c a r b o n y l. T h is i s sh o w n by t h e c u rv e b e c o m in g a
h o r i z o n t a l l i n e , i n d i c a t i n g no i n c r e a s e in d im e r p r o d u c ts a t a tim e c o r ­
r e s p o n d i n g to th e d i s a p p e a r a n c e o f t h e m e ta l c a rb o n y l b o n d s in th e i n f r a ­
re d s p e c tr u m (F ig u re s 2 7, 2 8).
To s u b s t a n t i a t e th e i d e a o f t h e n e c e s s i t y o f th e p r e s e n c e o f a
m e ta l c a r b o n y l , n o r b o r n a d ie n e w a s i r r a d i a t e d w ith >2 80 m p l i g h t a n d a l s o
w ith l i g h t o f < 2 8 0 mp. a n d no h y d ro c a rb o n d im e r p r o d u c ts w e re d e t e c t e d
b y t h e g a s c h r o m a to g r a p h .
CONCLUSION
Thus fa r th e i n t e r p r e t a t i o n o f th e d a t a h a s i n d i c a t e d th e p r e s e n c e
o f a com m on i n t e r m e d i a t e w h ic h i s form ed a f t e r th e s o l u t i o n h a s b e e n
irra d ia te d .
T his com m on in t e r m e d i a t e i s p r o p o s e d to b e n o rb o r n a d ie n e
chrom ium t e t r a c a r b o n y l s i n c e t h i s is. th e o n ly m e ta l c a r b o n y l i s o l a t e d
from a l l th e r e a c t i o n s w h e re p r o d u c ts a re fo rm ed . In a d d i t i o n , th e a p ­
p e a r a n c e o f th e d im e r c o r r e s p o n d s to th e a p p e a r a n c e o f n o rb o r n a d ie n e
chro m iu m t e t r a c a r b o n y l a n d w h e n n o rb o r n a d ie n e chrom ium t e tr a c a r b o n y l
i s a b s e n t no d im e r p r o d u c ts a re f o r m e d .
I t i s n e c e s s a r y a t t h i s p o in t to d i g r e s s for a m o m en t to d i s c u s s
h o w t h e n o rb o r n a d ie n e c o u ld be a t t a c h e d to th e chrom ium in th e d im e r i­
z a t i o n r e a c t i o n . There a re s e v e r a l p o s s i b i l i t i e s .
It c a n e i t h e r b e b o n d e d
e x o o r e n d o w h e n i t i s a s i n g l e b o n d a n d m u s t be e n d o w h e n b o th b o n d s
a r e b o n d e d to th e s a m e m e ta l (F ig u re 2 9 ).
endo
F ig . 2 9 .
exo
endo endo
P o s s i b l e w a y s fo r chrom ium to b o n d to n o r b o r n a d i e n e .
E l e c t r o p h i l i c a t t a c k on th e n o r b o r n a d ie n e i s u s u a l l y e x o (60) a n d in
t h e s i l v e r c o m p le x , C 7H g (AgNO3) 2 (3 0 ), th e s i l v e r h a s b e e n sh o w n by
X - r a y c r y s t a l s t r u c t u r e to e x i s t o n t h e e x o s i d e . Thus i t w o u ld s e e m
t h a t th e e x o s i d e is th e p r e f e r r e d s i d e .
61
I f th e n o r b o r n a d ie n e s h o u ld b o n d o n ly e x o to chrom ium i t i s d if f i­
c u l t to r a t i o n a l i z e h o w n o r b o r n a d ie n e chrom ium te t r a c a r b o n y l c o u ld e x i s t
s i n c e a l l th e n o r b o r n a d ie n e chrom ium b o n d s a re e n d o to n o r b o r n a d ie n e .
On th e o t h e r h a n d , i f n o rb o r n a d ie n e w o u ld b o n d o n ly e n d o to chrom ium i t
w o u ld be d i f f i c u l t to r a t i o n a l i z e h o w th e e x o tr a n s e n d o d im e r i s fo rm ed ,
e s p e c i a l l y s i n c e th e e x o t r a n s e n d o d im e r i s found in la r g e a m o u n ts in
a l l th e chrom ium c a s e s . A n o th er p o s s i b i l i t y i s t h a t n e i t h e r o f th e
n o r b o r n a d i e n e s i s b o n d e d to th e m e ta l w h e n th e d im e r iz a tio n o c c u r s , b u t
t h i s i s t e n t a t i v e l y e x c lu d e d b e c a u s e t h e p r o d u c ts v a r y w ith d if f e r e n t
m e ta ls.
Thus i f th e o n ly p u r p o s e o f th e m e ta l w a s to e x c i t e a n o n --
a t t a c h e d n o r b o r n a d ie n e , a l l th e c a s e s w h e re n o r b o r n a d ie n e w a s e x c i t e d ,
th e n o rb o r n a d ie n e w o u ld b e s im i l a r a n d o n e c o u ld e x p e c t i d e n t i c a l p r o ­
d u c ts b u t , a s a l r e a d y s t a t e d , th e p r o d u c ts do v a ry w ith d if f e r e n t m e t a l s .
■ A n o th er p o s s i b i l i t y is t h a t o n ly o n e n o rb o r n a d ie n e i s b o n d e d to th e
m e ta l w ith o n ly o n e d o u b le b o n d a n d t h e d im e r iz a tio n m a y th e n o c c u r b e ­
tw e e n th e d o u b le b o n d n o t a t t a c h e d to th e m e ta l a n d a n o rb o r n a d ie n e from
t h e s o l u t i o n . T h is i d e a h a s b e e n p r o p o s e d (51) a n d i s c u r r e n tly u n d e r I n i.
v e s t i g a t i o n . In th e c a s e o f chrom ium c a r b o n y l s , i t i s d i f f i c u l t to s e e
h o w t h i s s i n g l e b o n d e d n o r b o r n a d ie n e m e c h a n is m i s o c c u r r in g s i n c e i t
w o u ld b e n e c e s s a r y to form n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l ( i s o ­
l a te d ) a n d t h e n h a v e t h i s n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l re v e r t
b a c k to n o r b o r n a d ie n e chrom ium p e n t a c a r b o n y l b e fo re th e r e a c t i o n w o u ld •
go to p r o d u c t s .
62
O n e re m a in in g p o s s i b i l i t y i s t h a t b o th n o r b o r n a d ie n e s a re a t t a c h e d
to th e m e ta l a n d t h e y c a n b e a t t a c h e d e i t h e r e x o o r e n d o a n d c a n c h a n g e
from e x o to e n d o o r from e n d o to e x o . The v a l i d i t y o f t h i s s t a t e m e n t i s
sh o w n by th e fo llo w in g c a s e . A r e a c t i o n o f n e a t n o rb o r n a d ie n e w ith
n o r b o r n a d ie n e chrom ium te tr a c a r b o n y l a n d th e r e a c t i o n w ith th e v a r io u s
m e ta l c a r b o n y ls y ie ld i d e n t i c a l p r o d u c ts a n d in s im i l a r r a t i o s . T h u s ,
u n l e s s i t i s p r o p o s e d t h a t th e n o rb o r n a d ie n e c am e off c o m p le te ly a n d tw o
o t h e r n o r b o r n a d i e n e s r e p l a c e i t a n d w e n t on o n ly e x o , a t l e a s t o n e o f th e
n o r b o r n a d ie n e s a t t a c h e d to th e chrom ium w ill be b o n d e d e n d o s i n c e t h i s
n o rb o r n a d ie n e c am e from th e en d o b o n d e d n o rb o r n a d ie n e chrom ium
te tra c a rb o n y l.
But th e r e a c t i o n y i e l d e d th e e x o t r a n s exo d im e r in th e l a r g e s t
y i e l d , w h ic h i n d i c a t e s t h a t b o th th e n o r b o r n a d ie n e s w e re e x o b o n d e d to
th e c h ro m iu m . Thus w e m u s t c o n c lu d e e i t h e r th e e x o t r a n s e x o c a n b e
form ed from tw o n o r b o r n a d i e n e s , o n e o f w h ic h m u st b e b o n d ed , e n d o , o r
t h a t th e r e is so m e ty p e o f m e c h a n is m t h a t a llo w s th e n o rb o r n a d ie n e
w hich, is b o n d e d to th e chrom ium to c h a n g e from e n d o to e x o . A nother
p o in t fa v o rin g the. m e c h a n is m o f h a v in g b o th th e n o r b o r n a d ie n e s b o n d e d
to th e chrom ium i s t h a t th e m e ta l o r b i t a l c a n be u s e d to lo w e r th e s y m ­
m e try r e s t r i c t i o n s a n d th e a c t i v a t i o n e n e r g y (46, 47, 4 8 ).
The a u th o r h a s c h o s e n to i n t e r p r e t th e d a ta u s i n g th e l a s t p o s s i ­
b i l i t y a n d th e m e c h a n i s t i c c o n s e q u e n c e s a re d i s c u s s e d b e lo w .
63
In th e c a s e o f chrom ium h e x a c a r b o n y l , th e fo rm atio n o f n o r b o r n a d ie n e chrom ium t e t r a c a r b o n y l i s p r o p o s e d to b e form ed by th e r e a c t i o n
s e q u e n c e sh o w n in Fig u re 31.
C r(C O
C r(C O
)6
F ig . 3 0 .
)6
C r(C O
)5
+
C O
F o rm atio n o f n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l from
chrom ium h e x a c a r b o n y l .
The p h o to c h e m ic a l r e a c t i o n o f chrom ium h e x a c a r b o n y l g o in g to chromium
p e n t a c a r b o n y l is w e ll k n ow n a n d th e r e v e r s e p r o c e s s h a s b e e n sh o w n to
o c c u r w h en th e i r r a d i a t i o n is s t o p p e d . In th e e x p e r im e n t d e m o n s tra tin g
t h i s , th e o n ly c a r b o n m o n o x id e p r e s e n t w a s w h a t w a s g iv e n up by th e
chrom ium h e x a c a r b o n y l (61, 62). C hrom ium p e n ta c a r b o n y l i s re p o rte d to
h a v e th e c h a r a c t e r i s t i c s o f a n e l e c t r o n d e f i c i e n t m o le c u le a n d w ill th u s
bond to m an y m o le c u le s w h ic h w ill d o n a t e e l e c t r o n s to t h i s e le c tr o n d e ­
f i c i e n t s y s t e m (61, 62). S in c e a ll t h e r e a c t i o n s a re run in n e a t n o rb o r n a ­
d i e n e , w h ic h i s know n to b e a b l e to d o n a t e i t s pi e l e c t r o n s to m e ta l
s p e c i e s (T ab le I ) , i t i s r e a s o n a b l e t h a t n o rb o r n a d ie n e w ill a c t a s an
e l e c t r o n d o n o r a n d n o rb o r n a d ie n e chro m iu m p e n ta c a r b o n y l w ill be f o r m e d .
64
The s e c o n d p i b o n d o f th e a t t a c h e d n o r b o r n a d ie n e w ill th e n d i s p l a c e
a n o t h e r c a r b o n y l (45) a n d th e s t a b l e n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l w ill b e fo rm ed . T h is d i s p l a c e m e n t o f a c a r b o n y l b y a d o u b le bond
i s sh o w n to o c c u r g e n e r a l l y in m e ta l c a r b o n y ls (4 5 ). The f a c t th a t
n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l c a n b e form ed th e r m a lly from
chrom ium p e n t a c a r b o n y l a s in th e l a s t r e a c t i o n s t e p i s d e m o n s t r a t e d by
th e r e a c t i o n o f N - p y r i d i n e chrom ium p e n t a c a r b o n y l . W h e n N - p y r id in e
chrom ium p e n t a c a r b o n y l i s h e a t e d to r e f lu x w ith n o rb o r n a d ie n e a n d
m e th y l io d id e in te tr a h y d r o f u r a n t h e p r o d u c ts a re n o r b o r n a d ie n e chrom ium
t e t r a c a r b o n y l a n d N - m e th y l p y rid in iu m io d id e s a l t .
Even in th e c a s e o f
d i - N - d i p y r i d i n e chrom ium t e t r a c a r b o n y l , run u n d e r s i m i l a r c o n d i t i o n s ,
th e o n ly p r o d u c ts o f t h i s r e a c t i o n a r e n o rb o r n a d ie n e chrom ium t e t r a c a r ­
b o n y l a n d N - m e th y l p y rid in iu m i o d i d e .
In th e b e n z e n e , t o l u e n e a n d m e s i t y l e n e chrom ium tr i c a r b o n y l
r e a c t i o n s th e in f r a r e d s p e c t r a a n d m a s s s p e c t r a i n d i c a t e w h a t th e i n t e r ­
m e d ia te i s p r io r to th e fo rm a tio n o f n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l
a n d t h e p r o p o s e d m e c h a n is m i s s h o w n in Fig u re 3 1 . L ig h t i s a b s o r b e d
a n d a b e n z e n e rin g to chrom ium m e ta l b o n d i s b r o k e n . A gain w e h a v e a n
e l e c t r o n - d e f i c i e n t m e ta l c a r b o n y l in n e a t n o r b o r n a d ie n e . The n o rb o r n a ­
d ie n e d o n a t e s i t s p i e l e c t r o n from o n e d o u b le b o n d , form ing n o rb o r n a d ie n e
b e n z e n e chrom ium t r i c a r b o n y l , w h ic h i s th e n i s o l a t e d a s th e re d c o m p le x .
The re d c o m p le x i s t e n t a t i v e l y a s s i g n e d t h i s s tr u c tu r e i n s t e a d of th e
s t r u c t u r e w h e re th e n o r b o r n a d ie n e i s d o u b ly bonded; a n d t h e b e n z e n e rin g
s i n g l y b o n d e d b e c a u s e t h e m a s s s p e c tr u m i n d i c a t e s t h a t m o s t o f th e
65
F ig . 31.
F o rm atio n o f n o r b o r n a d ie n e chrom ium t e t r a c a r b o n y l from a re n e
chrom ium t r i c a r b o n y l .
la r g e r p e a k s c o n ta i n th e b e n z e n e r i n g , i n d i c a t i n g it is h e ld b e t t e r th a n
th e n o r b o r n a d ie n e . T his m o le c u le w o u ld t h e n , w h en i r r a d i a t e d , c h a n g e
to h a v in g th e n o r b o r n a d ie n e d o u b ly b o n d e d a n d th e b e n z e n e rin g s i n g ly
b o n d e d . The b e n z e n e rin g c o u ld th e n com e o ff a n d th e n o rb o r n a d ie n e
chro m iu m t r i c a r b o n y l re m a in in g w ill form n o r b o r n a d ie n e chrom ium
t e t r a c a r b o n y l by p ic k in g up a c a r b o n y l from th e s o l u t i o n .
C arb o n
m o n o x id e is s o lu b le in w a t e r to 2.3 v o lu m e s p e r 100 ml o f w a te r (6 3 ),
w h ic h is a p p r o x im a te ly 0.001 M . It i s a p p r e c i a b l y more s o l u b l e in o r ­
g a n i c s o l v e n t s (6 3 ). T his c a r b o n y l , w h ic h i s p ic k e d from th e s o l u t i o n ,
c a n com e from th e d e c o m p o s itio n o f s t a r t i n g m a te r ia l a n d a l s o from th e
m e ta l c a r b o n y l l e f t a f t e r d im e rs a re fo rm e d . The n o rb o r n a d ie n e chrom ium
tr i c a r b o n y l c o u ld a l s o form d in o r b o r n a d ie n e chrom ium tr i c a r b o n y l if th e
66
n o r b o m a d i e n e chrom ium t r i c a r b o n y l p i c k e d a n o th e r n o rb o r n a d ie n e m o le ­
c u le from th e s o l u t i o n i n s t e a d o f a c a r b o n y l .
B e c a u s e th e n o r b o r n a d ie n e i s p r e s e n t in s u c h la r g e a m o u n ts i t
w o u ld s e e m r e a s o n a b l e t h a t th e n o r b o r n a d ie n e chrom ium tr ic a f b o n y l
w o u ld b o n d w ith n o r b o r n a d ie n e i n s t e a d o f th e c a r b o n m o n o x id e , b u t th e
r e s u l t s i n d i c a t e n o r b o r n a d ie n e chrom ium te t r a c a r b o h y l i s fo rm ed . One
p o s s i b l e e x p l a n a t i o n i s t h a t s i n c e c a r b o n y l i s m uch s m a l l e r s t e r i c a l l y i t
i s f a v o r e d . In a d d i t i o n , i f n o r b o r n a d ie n e d o e s a t t a c h i t s e l f to th e
n o rb o r n a d ie n e chrom ium tr i c a r b o n y l t h e r e s u l t i s a s t a b l e m o l e c u l e ,
n o rb o r n a d ie n e chrom ium t e t r a c a r b o n y l , w h e r e a s i f a n o rb o r n a d ie n e
a t t a c h e s i t s e l f to n o rb o r n a d ie n e chrom ium t r i c a r b o n y l t h e p r o d u c t,
d in o r b o r n a d ie n e chrom ium t r i c a r b o n y l , h a s n o t b e e n i s o l a t e d a n d i s o n ly
p o stu la ted a s a tra n s ie n t in te rm e d ia te .
O n c e th e s t a b l e n o r b o r n a d ie n e chrom ium t e t r a c a r b o n y l i s fo r m e d ,
l i g h t m u s t b e a b s o r b e d to c a u s e t h e r e a c t i o n to c o n t i n u e . T hat i r r a d i a ­
t io n i s n e c e s s a r y i s s h o w n b y th e th e r m a l r e a c t i o n o f n o rb o r n a d ie n e
chrom ium t e t r a c a r b o n y l in n e a t n o r b o r n a d ie n e a t 6 5 ° C for 12 h o u r s , w h ic h
d o e s n o t g iv e a n y d im e r p r o d u c t , a n d th e s t a r t i n g m a t e r i a l c a n b e r e ­
c o v e r e d from th e s o l u t i o n . Thus i t i s p r o p o s e d t h a t a b s o r p t i o n o f lig h t
c a u s e s th e chrom ium to l o s e a n o t h e r c a r b o n y l a n d form a t r a n s i e n t
d in o r b o r n a d ie n e chrom ium t r i c a r b o n y l , o r th e a b s o r p tio n o f li g h t w ill
b re a k a n o r b o r n a d ie n e chrom ium b o n d , r e s u l t i n g in th e fo rm a tio n o f a
d in o r b o r n a d ie n e chrom ium t e t r a c a r b o n y l w h ic h w ill a c t a s a t r a n s i e n t
in te rm e d ia te .
67
In th e l a t t e r c a s e (F ig u re 3 2 ), u s i n g d in o rb o r n a d ie n e chromium
t e t r a c a r b o n y l , th e tw o n o r b o r n a d ie n e s w o u ld be s i t u a t e d s o a s to g iv e a s
p r o d u c ts V, VI a n d VII s i m i l a r to th e p r o d u c ts from th e th e rm a l r e a c t i o n o f
iro n d i c a r b o n y l , d in i t r o s y l a n d n o r b o r n a d ie n e (4 5 ). T h e s e p r o d u c ts a re
v i s u a l i z e d a s b e in g form ed w h e n th e 2 prr o r b i t a l s o f n o r b o r n a d ie n e a re
m ix e d w ith th e chrom ium d o r b i t a l s . O n c e t h i s m ix in g h a s o c c u r r e d th e
th e rm a l r e s t r i c t i o n r u le s p r o p o s e d by W o o d w ard a n d H offm an no lo n g e r
a p p ly (46, 47, 48), a n d th e d im e r iz a tio n w ill p r o c e e d to p r o d u c t th e rm a lly .
The m e ta l th u s h a s a d u a l ro le o f re m o v in g th e sy m m e try r e s t r i c t i o n a n d
lo w e rin g th e a c t i v a t i o n e n e r g y (46, 47, 4 8 ). It s h o u ld be p o in te d o u t h e re
t h a t in th e th e rm a l d im e r iz a tio n o f n o r b o r n a d ie n e u s in g m e ta l c a r b o n y ls
i t i s p o s t u l a t e d (45) t h a t o n e pi b o n d from e a c h n o rb o r n a d ie n e is fo rm ally
i n v o l v e d , b u t i t h a s a l s o b e e n s u g g e s t e d t h a t th e s e c o n d pi bond o f th e
n o r b o r n a d ie n e a l s o c o n t r i b u t e s to th e t r a n s i t i o n s t a t e (4 5 ). A p h o to ­
c h e m i c a l r e a c t i o n u s in g chrom ium h e x a c a r b o n y l a n d n o rb o r n e n e d i s s o l v e d
(V)
exo trans exo
F ig . 3 2 .
(VI)
exo trans endo
(VII)
endo trans endo
F o rm atio n o f d im e rs u s in g d in o r b o r n a d ie n e chrom ium
te tra ca rb o n y l.
68
in h e x a n e w a s run a n d no d im e r p r o d u c ts w e re d e t e c t e d in th e g a s c h r o ­
m a to g ra m , i n d i c a t i n g th e s e c o n d bond i s n e c e s s a r y e i t h e r to form th e
n o r b o r n a d ie n e chrom ium te t r a c a r b o n y l or in fo rm atio n o f th e f i r s t bond o f
n o rb o r n a d ie n e to th e m e ta l c a r b o n y l.
In th e fo rm er c a s e , w h e re a c a r b o n y l i s l o s t a n d r e p l a c e d b y a
n o rb o r n a d ie n e form ing d in o r b o r n a d ie n e chrom ium t r i c a r b o n y l , th e p r o d u c t
r e s u l t i n g from t h i s in te r m e d ia te i s th o u g h t to be a D i e l s - A l d e r ty p e d im e r
XIII s i m i l a r to c o b a l t t r i c a r b o n y l n i t r o s y l a n d n o r b o r n a d ie n e . The D i e l s A lder ty p e d im e r s h o u ld t h e n c l o s e p h o to c h e m ic a lly to form th e c a g e c o m ­
p o u n d found in s m a ll y i e l d in a l l th e r e a c t i o n s (F ig u re 3 3 ).
hv
cage
F ig . 3 3 .
F o rm atio n o f d im e r u s in g d in o rb o r n a d ie n e chrom ium t r i c a r b o n y l.
I t s h o u ld be p o in te d o u t t h a t , a lth o u g h it is p o s s i b l e to form th e
tw o d in o rb o r n a d ie n e s p e c i e s w ith o u t h a v in g to form n o rb o r n a d ie n e
chrom ium t e t r a c a r b o n y l , t h e e x p e r im e n t a l r e s u l t s s h o w n o rb o r n a d ie n e
chrom ium t e t r a c a r b o n y l is fo rm ed . In a d d i t i o n , w h en n o rb o r n a d ie n e
69
chrom ium t e t r a c a r b o n y l i s u s e d a s th e s t a r t i n g r e a c t a n t t e m p la te i t g iv e s
th e e x p e c t e d p r o d u c ts in a s im i l a r r a tio to th e o th e r r e a c t a n t t e m p l a t e s .
F u r th e r m o r e , d im e rs a r e n o t s e e n in th e g a s c h ro m a to g ra m u n til n o r b o r n a d i e n e chrom ium t e t r a c a r b o n y l is p r e s e n t in in fr a r e d s p e c t r a a n d th e y s to p
w hen it is a b se n t.
EXPERIMENTAL
R e a g e n ts
C hrom ium h e x a c a r b o n y l , b e n z e n e chrom ium t r i c a r b o n y l , to lu e n e
chrom ium t r i c a r b o n y l , m e s i t y l e n e chrom ium tr ic a r b o n y l a n d d ic u m e n e
ch ro m iu m w e re o b t a i n e d from Alfa I n o r g a n i c s , I n c . , a n d e x c e p t for
d ic u m e n e c h ro m iu m , w e re u s e d w ith o u t fu rth e r p u r i f i c a t i o n . D ic u m e n e
c h ro m iu m , a b l a c k v i s c o u s l i q u i d , w a s d i s t i l l e d u n d e r vacuum- (1 3 0 1 3 3 ^ /0 .1 -0 .2 mm) a n d u s e d im m e d ia te ly .
N o r b o r n a d ie n e chrom ium te t r a c a r b o n y l w a s p r e p a r e d a s d e s c r i b e d
b y B e n n e tt, P r a tt a n d W ilk in s o n (-64) b y tr e a tm e n t o f chrom ium .
h e x a c a r b o n y l w ith n o rb o r n a d ie n e a t e l e v a t e d t e m p e r a t u r e s . It w a s found
to b e form ed in h ig h e r y ie ld (50%) w h e n n o rb o r n a d ie n e a n d chrom ium
h e x a c a r b o n y l w e re i r r a d i a t e d for 24 hours. (> 2 8 0 mp) in a s e a l e d tu b e from
w h ic h th e a i r w a s re m o v e d . In b o th m e th o d s th e p r o d u c t w a s p u rifie d by
su b lim a tio n .
. . .
The n itr o g e n u s e d in a l l r e a c t i o n s in th e d e o x y g e n a tin g p ro c e d u re
w a s p u r if ie d by p a s s i n g i t th ro u g h BSTS c a t a l y s t (BASF C o lo rs & C h e m i­
c a l s , I n c . ) , w h ic h re m o v e d th e o x y g e n a n d w a t e r .
'
N o rb o rn a d ie n e w a s o b ta in e d from F rin to n L a b o r a t o r i e s . P u r if ic a tio n
w a s a c c o m p l i s h e d b y s itr r i n g i t o v e r a c t i v a t e d n e u tr a l a lu m in a for s e v ­
e r a l h o u rs a n d t h e n d i s t i l l i n g i t j u s t p rio r to u s in g i t .
N o rb o rn e n e w a s o b t a i n e d from A ld rich C h e m ic a l C o m p a n y , I n c . ,
and w as used as re c eiv e d .
71
I n s tr u m e n ts
In f ra r e d s p e c t r a w e re o b ta in e d u s in g e i t h e r a B eckm an IR -4 o r a
B eckm an I R - 5 -A in f r a r e d s p e c t r o p h o t o m e t e r . S p e c tra w e re ru n in s o lu tio n
u s i n g m a tc h e d liq u id in f r a r e d c e l l s w ith s o d iu m c h lo r id e w in d o w s . E a c h
s p e c tr u m w a s s t a n d a r d i z e d w ith th e p o l y s t y r e n e a b s o r p tio n p e a k a t
16 0 1 .8 c m \ .
N u c l e a r m a g n e t ic r e s o n a n c e s p e c t r a w e re o b ta in e d in s o lu tio n
u s i n g a V a ria n m o d el A - 6 0 , e x c e p t fo r th e c a g e c o m p o u n d w h ic h w a s run
u s i n g a V arian m o d e l A H - 100.
U l t r a v i o l e t s p e c t r a w e re o b t a i n e d in s o lu tio n u s in g m a tc h e d q u a rtz
c e l l s o n a C a ry M o d e l 14.
The g a s c h ro m a to g ra p h u s e d for p r o d u c t i d e n t i f i c a t i o n w a s a n F & M
M o d e l 400 g a s c h r o m a to g r a p h . The co lu m n w a s a g l a s s , 4 ' , 5% SE-30 on
G a s C h ro m -Z (1 0 0 -1 2 0 m e s h ) . The te m p e r a t u r e p rogram o f 7 5 ° C to 2 0 0 ° C
(7. ScVmin) w ith a flo w r a te o f 40 ml h e liu m p e r m in u te w a s u s e d for b e s t
s e p a r a t i o n . The th r e e d im e r c o m p o u n d s a n d s i n g le c a g e com p o u n d w e re
d e t e c t e d b e tw e e n 1 2 0 - 1 3 5 ° C a n d th e c a r b o n y l p r o d u c t w a s d e t e c t e d b e ­
tw e e n 1 5 8 - 1 6 0 ° C .
For p r o d u c t i s o l a t i o n a n A e ro g ra p h m o d e l A -700 A utoprep w a s u s e d .
A I/4 - i n c h o u t e r d ia m e te r 2 0 - f o o t alu m in u m co lu m n p a c k e d w ith 3 0 % SE -30
o n G a s C h ro m -Z (1 0 0 - 1 2 0 m esh ) w a s u s e d . The c h ro m a to g ra p h ic c o n d i ­
t i o n s w e re: c o lu m n , 1 8 0 °C ; c o l l e c t o r , 2 2 5 °C ; d e t e c t o r , 2 6 0 °C ; i n j e c t o r ,
2 5 0 °C ; flo w r a t e , 300 ml h e liu m p e r m in u te . U n d e r t h e s e c o n d itio n s th e
f i r s t d im e r a p p e a r e d in 88 m i n u t e s .
72
The s a m p l e s to he c h r o m a to g ra p h e d on th e A e ro g ra p h A utoprep w e re
f i l t e r e d th ro u g h a B u ch n er f u n n e l f il le d w ith a c t i v a t e d n e u t r a l a lu m in a to
re m o v e s o l i d p a r t i c l e s a n d c a r b o n y l p o l y m e r s . The a lu m in a w a s w a s h e d
w ith h e x a n e to e l u t e a l l th e d im e r a n d c a g e c o m p o u n d s , l e a v i n g b e h in d
th e chrom ium o x id e a n d m o s t o f th e c a r b o n y l i n s e r t i o n p r o d u c t. The
s o l u t i o n s w e re c o n c e n t r a t e d a n d i n j e c t e d in to th e A e ro g ra p h . P ro d u c ts
w e re e a s i l y s e p a r a t e d a n d i n t e g r a t i o n o f p e a k a r e a s u s in g a S a rg e n t
m o d e l SR r e c o r d e r a ffo rd e d a m e th o d to d e te r m in e d im e r p r o d u c t p e r c e n t ­
ages.
M a s s s p e c t r a w e re o b t a i n e d fo r th e c a g e c o m p o u n d from Purdue
U n i v e r s i t y on a H ila c h i R M U -GA. All o t h e r m a s s s p e c t r a d a t a w e re o b ­
t a i n e d on t h e V a ria n M a t C H 5 .
L ig h t a n d R e a c tio n S y s te m s
In a l l c a s e s th e l i g h t s o u r c e for t h e p h o to c h e m ic a l r e a c t i o n w a s a
H a n o v ia Type A 4 5 0 - w a t t h ig h p r e s s u r e m e rc u ry a r c . ■
S a m p le s w e re i r r a d i a t e d in a r e a c t i o n v e s s e l c o n s t r u c t e d of a P y re x
g l a s s v e s s e l t h a t w o u ld a c c o m m o d a te a q u a r tz or P y rex w a t e r - c o o l e d im ­
m e rs io n w e ll s u i t a b l e for h o ld in g th e lam p a n d a c i r c u l a r f i l t e r . The
b o tto m o f th e r e a c t i o n v e s s e l h a d a f i l t e r e d d i s k to a l l o w n itr o g e n to
b u b b le th ro u g h th e r e a c t i o n m ix tu re o u t a c o n d e n s e r c o n n e c t e d to a s id e
arm a n d th ro u g h a n itr o g e n b u b b le r . N itr o g e n w a s b u b b le d th ro u g h th e
r e a c t i o n mixture. 12 h o u rs b e fo re th e i r r a d i a t i o n w a s s t a r t e d to rem ove
d isso lv e d oxygen.
I m m e r s io n W e ll
R e a c tio n V e s s e l
Lamp
P h o to r e a c tio n fo r D e te rm in in g P ro d u c ts a n d P ro d u ct R a tio s
C hrom ium H e x a c a r b o n y l
To 70 ml o f p u r if ie d n o rb o r n a d ie n e 0.7 4 8 3 g (0 .0 0 3 5 mole) of
chrom ium h e x a c a r b o n y l w a s a d d e d . T his s o lu tio n w a s p l a c e d in th e
p h o to r e a c t o r a n d p u rif ie d n itr o g e n w a s b u b b le d th ro u g h th e s o lu tio n for
12 h o u r s . The l i g h t , w ith a c o r e x f i l t e r , w a s th e n tu rn e d o n a n d th e
i r r a d i a t i o n w a s run for 33 h o u r s . The n itr o g e n w a s b u b b le d th ro u g h th e
s o l u t i o n d u rin g th e c o m p le te r e a c t i o n . A g a s c h ro m a to g ra m w a s t a k e n o f
t h e t o t a l r e a c t i o n p r o d u c t , w h ic h w a s t h e n f il te r e d th ro u g h a Buchner
fu n n e ll f il le d w ith a c t i v a t e d n e u tr a l a lu m in a to rem o v e t h e s o lid m a te r ia l
( d e c o m p o s itio n p ro d u c t) a n d m o s t o f th e c a r b o n y l p o ly m e r. The a lu m in a
w a s w a s h e d w ith h e x a n e u n til no d im e rs w e re in th e f i l t r a t e . The h e x a n e
s o lu tio n w a s th e n c o n c e n t r a t e d to a v i s c o u s li q u i d . The v i s c o u s liq u id
w a s i n j e c t e d in to th e A ero g rap h A utoprep a n d fiv e f r a c t i o n s w ere
74
c o l l e c t e d . The fif th f r a c tio n c o n t a i n e d th r e e c o m p o n e n t s . The i n t e g r a ­
tio n o f th e p e a k s o f t h e g a s c h ro m a to g ra m w e re r e c o r d e d u s in g a S a rg e n t
m o d e l SR r e c o r d e r .
F r a c tio n I — I d e n tif i e d a s th e u n re m o v e d s o l v e n t .
F r a c tio n 2 — N u c l e a r m a g n e t ic r e s o n a n c e 1.23 , 1.32 , 1.69 , 2.62 ,
5.97.
G a s c h ro m a to g ra m
p e a k p e r c e n t a g e 36%
M e ltin g p o in t 6 7 - 6 8 ° C .
F r a c tio n 3 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .1 3 , 2 . 0 0 , 2 .5 4 , 2 .8 0 ,
5.82 , 6 .2 0 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 21%
F r a c tio n 4 — N u c l e a r m a g n e t ic r e s o n a n c e 1 . 0 2 , 1 . 5 5 , 1 .8 5 , 2.72 ,
6 .3 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 29%
F r a c tio n 5 — C o m p o n e n t I
N u c l e a r m a g n e t ic r e s o n a n c e 1.79 , 2 .4 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 14%
Com ponent 2
M e ltin g p o in t > 3 0 0 OC .
Com ponent 3
Not in v e stig ate d .
N o r b o r n a d ie n e C hrom ium T e tr a c a r b o n y l
To 70 ml o f p u r if ie d n o r b o r n a d ie n e 0 .2 4 4 6 g (0.0009 mole) of
n o r b o r n a d ie n e chrom ium te t r a c a r b o n y l w a s a d d e d . This s o lu tio n w a s .
75
p l a c e d in th e p h o to r e a c t o r a n d p u r if ie d n itr o g e n w a s b u b b le d th ro u g h th e
s o l u t i o n fo r 12 h o u r s .
The l i g h t , , w ith a co'rex f i l t e r , w a s t h e n tu rn e d .o n
a n d th e i r r a d i a t i o n w a s run fo r 24 h o u r s . The n itr o g e n w a s b u b b le d
th ro u g h th e s o lu tio n d u rin g th e c o m p le te r e a c t i o n . A g a s c h ro m ato g ram
w a s t a k e n o f th e t o t a l r e a c t i o n p r o d u c t, w h ic h w a s th e n f i l t e r e d th ro u g h
a B u ch n e r fu n n e l f i l l e d w ith a c t i v a t e d n e u t r a l a lu m in a to re m o v e th e s o lid
m a te r ia l ( d e c o m p o s itio n p ro d u c t) a n d m o s t o f th e c a r b o n y l p o ly m e r. The
a lu m in a w a s w a s h e d w ith h e x a n e u n til no d im e rs w e re in th e f i l t r a t e .
The h e x a n e s o l u t i o n w a s th e n c o n c e n t r a t e d to a v i s c o u s l i q u i d . The
v i s c o u s liq u i d w a s i n j e c t e d in to th e A e ro g ra p h A utoprep a n d fiv e f r a c ­
t i o n s w e re c o l l e c t e d .
The fif th f r a c tio n c o n ta i n e d th r e e c o m p o n e n t s . The
i n t e g r a t i o n o f th e p e a k s o f th e g a s c h ro m a to g ra m w e re r e c o r d e d u s in g a
S a r g e n t m o d e l SR r e c o r d e r .
F r a c tio n I — I d e n t i f i e d a s t h e u n re m o v e d s o l v e n t .
F r a c tio n 2 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .2 3 , 1 . 3 2 , 1 . 6 9 , 2 . 6 2 ,
5.97.
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 52%
M e lt in g p o in t 6 7 - 6 8 ° C .
F r a c tio n 3 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .1 3 , 2 . 0 0 , 2 .5 4 , 2 .8 0 ,
5 . 8 2 , 6 .2 0 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 20%
F r a c tio n 4 — N u c l e a r m a g n e t ic r e s o n a n c e 1.02 , 1 .5 5 , I. 8 5 , 2.72 ,
6 .3 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 20%
76
F r a c tio n 5 — C o m p o n e n t I
N u c l e a r m a g n e t ic r e s o n a n c e 1 .7 9 , 2 .4 5 .
G a s c h ro m ato g ram ' p e a k p e r c e n t a g e 5%.
Com ponent 2
M e ltin g p o in t > 3 0 0 ° C .
Com ponent 3
Not in v e s tig a te d .
B e n z e n e C hrom ium T ric a rb o n y l
To 70 ml o f p u r if ie d n o r b o r n a d ie n e 0.5842 g (0 .0 0 2 7 mole) of
b e n z e n e chrom ium tr i c a r b o n y l- w a s a d d e d . This s o lu tio n w a s p l a c e d in
t h e p h o to r e a c t o r a n d p u r if ie d n itr o g e n w a s b u b b le d th ro u g h th e s o lu tio n
for 12 h o u r s . The l i g h t , w ith a c o r e x f i l t e r , w a s th e n tu r n e d on a n d th e
i r r a d i a t i o n w a s run fo r 24 h o u r s . The n itr o g e n w a s b u b b le d th ro u g h th e
s o l u t i o n d u rin g th e c o m p le te r e a c t i o n . A g a s c h ro m a to g ra m w a s t a k e n o f
th e t o t a l r e a c t i o n p r o d u c t , w h ic h w a s t h e n f il te r e d th ro u g h a B uchner
fu n n e l f i l l e d w ith a c t i v a t e d n e u t r a l a lu m in a to rem ove th e s o lid m a te r ia l
( d e c o m p o s it io n p ro d u c t) a n d m o s t o f th e c a r b o n y l p o ly m e r. The a lu m in a
w a s c o m b in e d w ith h e x a n e u n til no d im e rs w e re in th e f i l t r a t e . The
h e x a n e s o l u t i o n w a s th e n c o n c e n t r a t e d to a v i s c o u s l i q u i d .
The v i s c o u s
li q u i d w a s i n j e c t e d in to th e A ero g rap h A utoprep a n d fiv e f r a c tio n s w e re
c o l l e c t e d . The fifth f r a c tio n c o n ta i n e d th r e e c o m p o n e n t s . The i n t e g r a ­
tio n o f th e p e a k s o f th e g a s c h ro m a to g ra m w e re r e c o r d e d u s in g a S a rg e n t
m o d e l SR r e c o r d e r .
77
F r a c tio n I — I d e n t i f ie d a s th e un’r e m o v e d s o l v e n t .
F r a c tio n 2 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .2 3 , 1.32 , 1 .6 9 , 2. 62 ,
5.97.
• G a s c h ro m a to g ra m p e a k p e r c e n t a g e 36%.
M e lt in g p o in t 6 7 - 6 8 ° C .
F r a c tio n 3 — N u c l e a r m a g n e tic r e s o n a n c e 1 .1 3 , 2 . 0 0 , 2 .5 4 , 2 .8 0 ,
5 . 8 2 , 6 .2 0 .
' G a s c h ro m a to g ra m p e a k p e r c e n t a g e 2 4%.
F r a c tio n 4 — N u c l e a r m a g n e t ic r e s o n a n c e I. 02 , 1.55 , 1.85 , 2.72 , ■
6 .3 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 33%.
F r a c tio n 5 — C o m p o n e n t I
N u c l e a r m a g n e t ic r e s o n a n c e 1 .7 9 , 2 .4 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 7%.
Com ponent 2
M e ltin g p o in t > 3 0 0 ° C .
Com ponent 3
N ot in v e stig a te d .
T o lu e n e C hrom ium T ric a rb o n y l
To 70 ml o f p u r if ie d n o r b o r n a d ie n e 0.1123 g (0 .0 0 0 4 mole), o f t o l u e n e
chrom ium tr i c a r b o n y l w a s a d d e d . T h is s o lu tio n w a s p l a c e d in th e p h o to
r e a c t o r a n d p u r if ie d n itr o g e n w a s b u b b le d th ro u g h th e s o l u t i o n for 12
h o u r s . The l i g h t , w ith a c o r e x f i l t e r , - w a s then, tu rn e d o n a n d th e i r r a d i tio n w a s run for 24 h o u r s . The n itr o g e n w a s b u b b le d th ro u g h th e s o lu tio n
78
d u rin g th e c o m p le te r e a c t i o n . A g a s c h ro m a to g ra m w a s t a k e n o f th e t o t a l
r e a c t i o n p r o d u c t , w h ic h w a s th e n f i l t e r e d th ro u g h a B u ch n e r fu n n e l f i l l e d
w ith a c t i v a t e d n e u t r a l a lu m in a to re m o v e th e s o lid m a t e r i a l ( d e c o m p o s i­
t io n p ro d u c t) a n d m o s t o f th e c a r b o n y l p o ly m e r. The a lu m in a w a s w a s h e d
w ith h e x a n e u n til no d im e rs w e re in. th e f i l t r a t e . The h e x a n e s o lu tio n w a s
t h e n c o n c e n t r a t e d to a v i s c o u s l i q u i d . The v i s c o u s li q u i d w a s i n j e c t e d
in to th e A ero g rap h A utoprep a n d fiv e f r a c t i o n s w e re c o l l e c t e d . The fifth
f r a c tio n c o n t a i n e d t h r e e c o m p o n e n t s . The i n t e g r a t i o n o f th e p e a k s o f th e
g a s c h ro m a to g ra m w e re r e c o r d e d u s in g a S a rg e n t m o d el SR r e c o r d e r .
F r a c tio n I — I d e n t i f i e d a s t h e u n re m o v e d s o l v e n t .
F r a c tio n 2 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .2 3 , 1 .3 2 , 1.69 , 2 .6 2 ,
5.9 7.
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 49%.
M e ltin g p o in t 6 7 - 6 8 ° C .
F r a c tio n 3 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .1 3 , 2 .0 0 , 2 .5 4 , 2 .8 0 ,
5.82 , 6 .2 0 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 22%.
F r a c tio n 4 — N u c l e a r m a g n e t ic r e s o n a n c e 1.02 , 1 .5 5 , 1 .8 5 , 2 .7 2 ,
6 .3 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 22%.
79
F r a c tio n 5 — C o m p o n e n t I
N u c l e a r m a g n e t ic .r e s o n a n c e 1 .7 9 , 2 .4 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 7%.
Com ponent 2
M e lt in g p o in t > 3 0 0 ° C .
Com ponent 3
N ot in v e stig a te d .
M e s i t y l e n e C hrom ium T ric a rb o n y l
To 70 ml o f p u r if ie d n o r b o r n a d ie n e 0.1045 g . (0 .0 0 0 4 mole) of
m e s i t y l e n e chrom ium tr i c a r b o n y l w a s a d d e d . The s o l u t i o n w a s p l a c e d in
th e p h o to r e a c t o r a n d p u r if ie d n itr o g e n w a s b u b b le d th ro u g h th e s o lu tio n
for 12 h o u r s . The l i g h t , w ith a c o r e x f i l t e r , w a s th e n tu rn e d on a n d th e
i r r a d i a t i o n w a s run fo r 24 h o u r s . The n itr o g e n w a s b u b b le d th ro u g h th e
s o l u t i o n d u rin g th e c o m p le te r e a c t i o n . A g a s c h ro m a to g ra m w a s t a k e n o f
th e t o t a l r e a c t i o n p r o d u c t , w h ic h w a s t h e n f il te r e d th r o u g h a B uchner
fu n n e l f i l l e d w ith a c t i v a t e d n e u t r a l a lu m in a to rem ove t h e s o lid m a te r ia l
( d e c o m p o s it io n p ro d u c t) a n d m o st o f th e c a r b o n y l p o ly m e r.
The a lu m in a
w a s w a s h e d w ith h e x a n e u n til no d im e rs w e re in th e f i l t r a t e . The h e x a n e
s o l u t i o n w a s th e n c o n c e n t r a t e d to a v i s c o u s l i q u i d . The liq u id o il w a s
i n j e c t e d in to th e A e ro g ra p h A utoprep a n d fiv e f r a c t i o n s w e re c o l l e c t e d .
The fifth f r a c tio n c o n t a i n e d th r e e c o m p o n e n t s . The i n t e g r a t i o n o f th e
p e a k s o f th e g a s c h ro m a to g ra m w e re r e c o r d e d u s in g a S a rg e n t m odel SR
recorder.
80
F r a c tio n I — I d e n t i f ie d a s th e u n r e m o v e d s o l v e n t .
F r a c tio n 2 — .N u c le a r m a g n e t ic r e s o n a n c e 1 .2 3 , 1.32 , 1 .6 9 , 2.62 ,
5.97.
G a s ch ro m a to g ra m p e a k p e r c e n t a g e 39%
M e ltin g p o in t 6 7 - 6 8 ° C .
F r a c tio n 3 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .1 3 , 2 . 0 0 , 2 .5 4 , 2 .8 0 , .
5 . 8 2 , 6. 2 0 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 2 6%.
F r a c tio n 4 — N u c l e a r m a g n e t ic r e s o n a n c e 1 .0 2 , 1 .5 5 , 1 .8 5 , 2 .7 2 ,
6 .3 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 26%.
F r a c tio n 5 — C o m p o n e n t I
N u c l e a r m a g n e tic r e s o n a n c e 1 .7 9 , 2 .4 5 .
G a s c h ro m a to g ra m p e a k p e r c e n t a g e 9%.
Com ponent 2
M e ltin g p o in t > 3 0 0 ° C .
Com ponent 3
Not in v e stig a te d .
D ic u m e n e C hromium
To 70 ml o f p u r if ie d n o rb o r n a d ie n e 0.4 ml (= 0.0012 m ole) of
d ic u m e n e chrom ium w a s a d d e d . This s o lu tio n w a s p l a c e d in th e p h o to
r e a c t o r a n d p u r if ie d n itr o g e n w a s b u b b le d th ro u g h th e s o l u t i o n for 12
h o u r s . The l i g h t , w ith a c o r e x f i l t e r , w a s t h e n tu rn e d on a n d th e i r r a d i ­
a tio n w a s run for 24 h o u r s . The n itr o g e n w a s b u b b le d th ro u g h th e
81
s o l u t i o n d u rin g th e c o m p le te r e a c t i o n . A g a s c h ro m a to g ra m w a s ta k e n of.
th e r e a c t i o n m ix tu re a f t e r 24 h o u r s , a n d s h o w e d no h y d ro c a rb o n d im e r s .
I s o l a t i o n o f P h o to r e a c tio n I n te r m e d ia te s
C hrom ium H e x a c a r b o n y l
To 70 ml o f p u r if ie d n o rb o r n a d ie n e 0.1 9 2 0 g (0.0009 m ole) of
chrom ium h e x a c a r b o n y l w a s a d d e d a n d th e s o lu tio n w a s p u t in to th e
p h o to r e a c t o r . • P u rifie d n itr o g e n w a s b u b b le d th ro u g h th e s o lu tio n for 12
-I
h o u r s . An in f r a r e d s p e c tru m w a s t h e n t a k e n (in fra re d s p e c tru m 1988 cm ,
F ig u re 7) a n d th e l i g h t , w ith a p y re x f i l t e r , w a s tu r n e d o n . In fra re d
s p e c t r a w e re t a k e n a t o n e - h a l f h o u r i n t e r v a l s for s e v e n h o u rs (in fra re d '
s p e c t r a a f t e r tw o h o u rs 2 0 3 3 , 1 9 5 9 , 1 9 4 4 , 1913 cm \ F ig u re 8) . After a
t o t a l i r r a d i a t i o n tim e o f t e n h o u rs a n o t h e r in f r a r e d s p e c tr u m w a s ta k e n
a n d c o m p a re d to th e o n e t a k e n a t s i x h o u r s . The c o m p a r is o n s h o w e d no
c h a n g e s o th e i r r a d i a t i o n w a s s t o p p e d (in fra re d s p e c tru m a f t e r s ix h o u r s ,
no m e ta l c a r b o n y l b a n d s . F ig u re 9 ).
A n o th er r e a c t i o n s o l u t i o n , in w h ic h 0.2 0 0 7 g (0 .0 0 0 9 mole) o f
chro m iu m h e x a c a r b o n y l w a s a d d e d to 70 ml o f p u rif ie d n o r b o r n a d ie n e , h a d
p u r if ie d n itr o g e n b u b b l e d 't h r o u g h a s b e f o r e . An in f r a r e d s p e c tru m w a s
t a k e n (in fra re d s p e c tru m a t z e ro tim e 1988 c m / ) a n d t h e l i g h t , w ith a
p y re x filte r,, w a s tu rn e d o n . The r e a c t i o n w a s run fo r tw o h o u r s , th e n th e
i r r a d i a t i o n w a s s to p p e d a n d a n i n f r a r e d s p e c tru m t a k e n (in fra re d s p e c tru m
a f t e r tw o h o u rs 2 0 3 3 , 1 9 5 9 , 1 9 4 4 , 1913 cm *). The r e a c t i o n s o lu tio n w a s
a l l o w e d to s t a n d u n d e r n itr o g e n for 19 h o u r s . I n f r a r e d s p e c t r a w e re t a k e n
a t t w o - h o u r i n t e r v a l s a n d r e a c h e d a m axim um c h a n g e in s i x h o u rs a f t e r
82
i r r a d i a t i o n w a s s to p p e d (in fra re d .sp ectru m a f t e r s i x h o u rs 2 0 3 3 , 1 9 8 8 ,
1 9 5 9 , 1 9 4 4 , 1913 cm \ F ig u re 10). A fter th e s o lu tio n s a t for 19 h o u rs i t
w a s h e a t e d to 7 0 ° C fo r fiv e h o u rs w ith h o a p p a r e n t c h a n g e o c c u r rin g in
th e in fr a r e d s p e c tr u m . The s o lu tio n w a s th e n c o o le d to room te m p e ra tu re
a n d th e l i g h t , w ith a p y re x f i l t e r , tu r n e d oh for 30 m in u te s b e fo re an
in f r a r e d s p e c tru m w a s t a k e n (in fra re d s p e c tru m a f te r 30 m in u te s 2 0 3 3 ,
-I
1 9 5 9 , 1 9 4 4 , 1913 cm ) . The r e a c t i o n m ix tu re w a s re m o v e d from th e p h o to
r e a c t o r a n d ro to e v a p o r a t e d to a v o lu m e o f 5 m l. The 5 -m l c o n c e n tr a te
w a s c h ro m a to g ra p h e d o n a n a c t i v a t e d s i l i c a g e l c o lu m n .
H exane was
a d d e d to re m o v e a n y h y d ro c a rb o n d im e rs a n d u n til a b r ig h t y e llo w -b a n d
s t a r t e d to be e l u t e d . An in f r a r e d s p e c tr u m w a s t a k e n o f a l l th e h e x a n e
f r a c t i o n s a f t e r th e y w e re c o m b in e d a n d c o n c e n t r a t e d , b u t t h e in fra re d
s p e c tru m s h o w e d no m e ta l c a r b o n y l b a n d s . B en z e n e w a s a d d e d to th e
s i l i c a g e l co lu m n a n d th e b rig h t y e llo w b a n d c o l l e c t e d . The b e n z e n e w a s
re m o v e d a n d ro to e v a p o r a t e d . The r e s i d u e w a s s u b lim e d a n d an in fr a r e d
s p e c tr u m (in fra re d s p e c tru m 2 0 3 3 , 1959 , 1 9 4 4 , 1913 cm ) a n d n u c l e a r
m a g n e t ic r e s o n a n c e s p e c tr u m ( n u c l e a r m a g n e t ic r e s o n a n c e s p e c tru m
4.42 [ 4 H ] , 3.63 [ 2 H ] , 1.30 [2 H ]) w e re t a k e n .
B en z e n e Chrom ium T ric a rb o n y l
To 70 ml o f p u r if ie d n o r b o r n a d ie n e 0.2135 g (0 .0 0 1 0 m ole) o f
b e n z e n e chrom ium tr i c a r b o n y l w a s a d d e d a n d th e s o l u t i o n w a s p u t intoth e p h o to r e a c t o r . P u rifie d n itr o g e n w a s b u b b le d th ro u g h th e s o lu tio n for
-I
12 h o u r s . An in f r a r e d s p e c tru m t a k e n (in f ra re d s p e c tru m 1 9 7 6 , 1905 cm ,
F ig u re 19), a n d th e l i g h t , w ith a p y r e x f i l t e r , w a s tu r n e d o n . In fra re d
83
s p e c t r a o f th e r e a c t i o n s o l u t i o n w e re t a k e n a t h a l f - h o u r i n t e r v a l s for 3 Vz
h o u rs ( in f ra re d s p e c tru m a f t e r 30 m in u te s 2 0 3 0 , I 9 6 0 , 1 9 4 4 , 1905,
_i
1861 cm , F ig u re 20; in f r a r e d s p e c tr u m a f t e r o n e h o u r 2 0 3 0 , 1 9 6 0 , 1 9 4 4 ,
-I
1907, 1961 cm , F ig u re 21). After a t o t a l r e a c t i o n tim e o f 5 Yz h o u rs an
in f r a r e d s p e c tru m w a s t a k e n a n d c o m p a re d to th e in f r a r e d s p e c tru m t a k e n
a t 3 ]/z h o u r s . No c h a n g e w a s o b s e r v e d . The i r r a d i a t i o n w a s s to p p e d '
(in f ra re d s p e c tr u m a f t e r 3 Yz h o u r s , no m e ta l c a rb o n y l b a n d s , Fig u re 2 2 ).
T o lu e n e C hromium T ric a rb o n y l
To 70 ml o f p u r if ie d n o rb o r n a d ie n e 0.22 73 g (0 .0 0 1 0 mole) o f t o l u e n e
chrom ium tr i c a r b o n y l w a s a d d e d a n d t h e s o l u t i o n w a s p u t in to th e p h o to
r e a c t o r . P u rifie d n itr o g e n w a s b u b b le d th ro u g h th e s o l u t i o n for 12 h o u r s . ■
An in f r a r e d s p e c tru m w a s t a k e n (in f ra re d s p e c tru m 1971 , 1900 cm \ Fig u re
2 3 ), a n d t h e l i g h t , w ith a p y r e x f i l t e r , w a s tu rn e d o n . In f ra r e d s p e c t r a
o f th e r e a c t i o n s o l u t i o n w e re t a k e n a t h a l f - h o u r i n t e r v a l s for 3 Yz h o u rs
(in f ra re d s p e c tr u m a f t e r 30 m in u te s 2 0 3 0 , 1 9 7 1 , 19 6 0 , 1 9 4 4 , 1907,
1860 cm \ Fig u re 24; i n f r a r e d s p e c tr u m a f t e r o n e h o u r 2 0 3 0 , 19 60, 1942 ,
1 9 1 0 / 1 8 6 0 cm \ F ig u re 2 5 ). A fter a t o t a l r e a c t i o n tim e o f 5 Y l h o u rs a n
in f r a r e d s p e c tr u m w a s t a k e n a n d c o m p a re d to th e in f r a r e d s p e c tru m t a k e n
a t 3 Y l h o u r s . No c h a n g e w a s o b s e r v e d a n d th e i r r a d i a t i o n w a s s to p p e d
(in f ra re d s p e c tr u m a f t e r 3 Yz h o u r s , n o m e ta l c a rb o n y l b a n d s . Figure 2 6 ).
M e s i t y l e n e Chrom ium T ric a rb o n y l
To 70 ml o f p u r if ie d n o rb o r n a d ie n e 0 .2 5 8 8 g (0 .0 0 1 0 mole) o f .
m e s i t y l e n e chrom ium t r i c a r b o n y l w a s a d d e d a n d t h i s s o l u t i o n w a s p u t
in to th e p h o to r e a c t o r . P u rifie d n itr o g e n w a s b u b b le d th ro u g h th e
94
s o l u t i o n for 12 h o u r s . .An in f r a r e d s p e c tr u m w a s th e n t a k e n (in fra re d s p e c trum 1 9 6 3 , 1889 cm , F ig u re 11) a n d t h e l i g h t , w ith a p y re x f i l t e r , w a s
tu r n e d o n . In f ra r e d s p e c t r a w e re t a k e n o f th e r e a c t i o n s o l u t i o n a t o n e h a l f i n t e r v a l s (in fra re d s p e c tr u m a f t e r 30 m in u te s 1 9 0 8 , 1860 cm- *. Fig u re
12; in f r a r e d s p e c tru m a f t e r tw o h o u rs 2 0 3 0 , 19 60, 1 9 4 0 , 1 9 0 9 , 1860 cm *,
F ig u re 13). A fter a t o t a l i r r a d i a t i o n tim e o f 5 1/2 h o u rs a n in f r a r e d s p e c tru m
w a s t a k e n a n d c o m p a re d to th e in f r a r e d s p e c tru m t a k e n a f t e r 3 I/2 h o u r s .
The c o m p a r is o n s h o w e d no c h a n g e in th e m e ta l c a r b o n y l re g io n o f th e
in f r a r e d s p e c t r a s o th e i r r a d i a t i o n w a s s to p p e d ..(infrared s p e c tru m a f te r
3 I/2 h o u rs , no m e ta l c a r b o n y l b a n d s , F ig u re 14).
A n o th er r e a c t i o n s o l u t i o n o f 0 .2 2 4 7 g (0.0009 mole) o f m e s i ty le n e
chrom ium tr i c a r b o n y l w a s run a s b e f o r e . A fter a t o t a l i r r a d i a t i o n tim e o f
S O m in u tes th e i r r a d i a t i o n w a s s to p p e d a n d th e s o lu tio n w a s d iv id e d in to
tw o p a r t s . O n e p a r t w a s a llo w e d to s t a n d in th e d a r k . An in fr a r e d s p e c ­
tru m w a s t a k e n a f t e r s i x h o u rs (in fra re d s p e c tru m 1 9 6 3 , 1 9 1 0 , 1889,
19 60 cm *, F ig u re 15). The o th e r h a l f o f th e r e a c t i o n m ix tu re w a s t a k e n to
d r y n e s s in a ro to e v a p o r a to r u s in g w a t e r a t room te m p e r a t u r e for th e
w a t e r b a t h . The r e s i d u e a f t e r th e s o l v e n t w a s re m o v e d w a s a r e d - y e l l o w
s o l i d . The r e d - y e l l o w s o lid w a s p u t in to a s u b lim a to r a n d h e a t e d to
3 5 ° C . A y e llo w s o l i d w a s c o l l e c t e d a n d th e red s o lid re m a in e d a t th e
b o tto m o f th e s u b lim a to r . The re d s o l i d w a s h e a te d to 7 0 ° C in th e s u b ­
lim a to r b u t re m a in e d u n c h a n g e d in th e b o tto m o f th e s u b lim a to r .
. The r e a c t i o n w a s re ru n a n d m ore o f th e y e llo w s o l i d c o l l e c t e d . A
n u c l e a r m a g n e t ic r e s o n a n c e s p e c tru m ( n u c l e a r m a g n e t ic r e s o n a n c e
85
s p e c tru m 4.42 [ 4 H ] , 3.73 [2 H ], 1 .3.0 [2 H J ), an in f r a r e d s p e c tru m ( in f r a —1
re d s p e c tru m 2 0 3 3 , 1959 , 1 9 4 4 , 1913 cm ) , a n d a m a s s s p e c tr u m (m a s s
• s p e c tru m . F ig u re 16) w e re t a k e n o f th e y e llo w s o l i d .
The re d c o m p le x w a s a l s o c o l l e c t e d a n d an in f r a r e d s p e c tru m
(in f ra re d s p e c tr u m 1 8 7 0 , 182 0 cm *, F ig u re 17) w a s t a k e n o f th e re d c o m ­
p l e x u s in g a p o t a s s i u m b ro m id e p e l l e t .
The re d c o m p le x d e c o m p o s e d in
m an y s o l v e n t s e v e n w h e n th e o x y g e n w a s re m o v e d b y b u b b lin g n itr o g e n
th ro u g h th e s o l v e n t . The s o l v e n t s w e re h e x a n e , p e tro le u m e t h e r , c a rb o n
t e t r a c h l o r i d e , c h lo r o f o r m , d im e th y l fo rm a m id e , d im e th y l s u l f o x i d e ,
b e n z e n e , e th a n o l a n d m e th a n o l.
A n o th er s i m i l a r r e a c t i o n w a s run a n d t h e re d s o lid c o l l e c t e d a n d
p u r if ie d w ith o u t h e a t i n g a b o v e 3 5 ° C . I t w a s p u rif ie d b y s u b lim in g th e
y e llo w s o l i d a w a y a t 3 5 ° C . To c h e c k th e re d c o m p le x for th e rm a l s t a ­
b i l i t y , a m a s s s p e c tr u m w a s run a t 2 0 o C , 2 5 ° C , 50o C , 7 0 ° C , 9 0 ° C a n d
115°C .
P h o to c h e m ic a l Time S tu d y
For th e tim e s t u d i e s s o l u t i o n s o f n o rb o r n a d ie n e a n d e i t h e r
chrom ium h e .x ac a rb o n y l 0 .2 7 0 7 g (0.0 0 1 2 m ole) or m e s i t y l e n e chromium
t r i c a r b o n y l 0 .2 7 7 6 g (0.0011 mole) w e re u s e d . In e a c h o f t h e s e s t u d i e s
p u rif ie d n itr o g e n w a s b u b b le d th ro u g h th e s o lu tio n fo r 12 h o u rs and th e n
t h e l i g h t , u s i n g a c o re x f i l t e r , w a s tu rn e d o n . ,
In t h e c a s e o f chrom ium h e x a c a r b o n y l , g a s c h ro m a to g ra m s of
s a m p l e s o f th e r e a c t i o n s o lu tio n w e re t a k e n a t o n e - h o u r in t e r v a l s for 14
h o u rs a n d t h e n a t lo n g e r i n t e r v a l s for a t o t a l tim e o f th r e e d a y s . A p lo t
86
s h o w in g p e a k h e i g h t s o f th e h y d ro c a rb o n d im e r v e r s u s tim e is sh o w n in
F ig u re 27.
In th e c a s e o f m e s i t y l e n e chrom ium t r i c a r b o n y l , g a s c h ro m a to g ra m s
w e re t a k e n e v e r y h a l f - h o u r for 2 1/2 h o u rs a n d th e n a t lo n g e r in t e r v a l s for
a t o t a l o f th r e e d a y s . A p l o t s h o w in g p e a k h e ig h ts v e r s u s tim e is sh o w n
in F ig u re 2 8 .
B e e r's Law
For th e s tu d y a s o l u t i o n o f I ml o f n o rb o r n a d ie n e in 99 ml of
c y c l o h e x a n e w a s p r e p a r e d . To t h i s chrom ium h e x a c a r b o n y l w a s a d d e d
u n til a s a t u r a t e d s o lu tio n w a s m a d e . A n o th e r s a t u r a t e d s o lu tio n o f
chro m iu m h e x a c a r b o n y l w a s a l s o p r e p a r e d in c y c lo h e x a n e b u t no n o rb o rn ­
a d i e n e w a s a d d e d . The u l t r a v i o l e t s p e c t r a w e re ru n o n t h e s e tw o s o l u ­
tio n s and com pared.
In fra re d S tu d y
Two s o l u t i o n s o f chrom ium h e x a c a r b o n y l in n o r b o r n a d ie n e w e re
p r e p a r e d . O ne s o l u t i o n c o n t a i n e d 0 .0 3 7 8 g (0.0017 mole) chromium
h e x a c a r b o n y l in 10 ml o f n o rb o r n a d ie n e a n d o n e c o n t a i n e d 0.0 5 3 7 g (0 .0 0 2 4
m ole) chrom ium h e x a c a r b o n y l in 10 ml o f n o r b o r n a d i e n e . The in fra re d
s p e c t r a o f t h e s e s o l u t i o n s w e re c o m p a re d in th e m e ta l c a r b o n y l re g io n to
th e in f r a r e d s p e c tru m o f chrom ium h e x a c a r b o n y l in c a r b o n t e t r a c h l o r i d e . •
T herm al R e a c tio n o f C hrom ium H e x a c a r b o n y l a n d N o rb o rn a d ie n e ■
For t h i s s tu d y 0 .0 2 6 2 5 g (0 .0 0 1 2 m ole)' of chrom ium h e x a c a r b o n y l
w a s p l a c e d in th e la r g e p h o t o r e a c t o r w ith 70 ml o f n o r b o r n a d ie n e .
87
P u rifie d n itr o g e n w a s b u b b le d th ro u g h th e s o l u t i o n . The s o lu tio n w a s
th e n h e a t e d , b y m e a n s o f a h e a t i n g ta p e w ra p p e d a ro u n d th e r e a c tio n
v e s s e l , to 5 7 ° C for 24 h o u r s . The s a m e s o lu tio n w a s t h e n h e a te d to
8 3 ° C for 24 h o u rs a n d f i n a l l y i t w a s h e a t e d to 8 9 ° C for 24 h o u r s . In fra re d
s p e c t r a w e re t a k e n e v e r y 24 h o u rs (in f ra re d s p e c tru m a t z e r o tim e
-I
-I
1988 cm ; in f r a r e d s p e c tru m o f th e fin a l s o lu tio n 1988 cm ) . A g a s
c h ro m a to g ra m w a s t a k e n e v e r y 2 4 h o u rs .
I r r a d i a tio n o f N o rb o rn a d ie n e W ith o u t M e ta l C arb o n y l
For t h i s s tu d y 70 ml o f p u rif ie d n o rb o r n a d ie n e w h ic h h a d n itr o g e n
b u b b le d th ro u g h i t w a s i r r a d i a t e d w ith l i g h t , u s in g a q u a r tz f i l t e r , for s i x
h o u r s . A g a s c h ro m a to g ra m w a s t a k e n a f t e r t h i s s i x h o u rs a n d s h o w e d no
h y d ro c a rb o n d im e rs p r e s e n t .
The s a m e s a m p le w a s t h e n i r r a d ia te d w ith
l i g h t , u s i n g a c o r e x f i l t e r , for 12 more h o u r s . A g a s c h ro m a to g ra m w a s
t h e n t a k e n a n d s h o w e d no h y d ro c a rb o n d i m e r s .
P h o to r e a c tio n o f N o rb o rn e n e
In t h i s s tu d y 6.984 g (0.0 7 4 3 mole) o f n o rb o rn e n e w a s d i s s o l v e d in
70 ml o f c y c l o h e x a n e a n d 0.2 7 2 3 g (0.0 0 1 2 mole) o f chrom ium h e x a c a r b o n y l
w a s a d d e d . N itro g e n w a s b u b b le d th ro u g h th e s o l u t i o n fo r s e v e n h o u r s .
Then th e s o lu tio n w a s i r r a d i a t e d , u s in g a c o re x f i l t e r , for 24 h o u r s . A
g a s c h ro m a to g ra m w a s t a k e n a n d s h o w e d no h y d ro c a rb o n d im e rs h ad b e e n
fo rm e d .
T h erm al R e a c tio n o f P y rid in e C hromium P e n ta c a r b o n y l a n d N o rb o rn a d ie n e
For t h i s r e a c t i o n , 0.2 3 0 3 g (0 .0 0 0 8 mole) o f p y rid in e -c h ro m iu m
p e n t a c a r b o n y l (65) w a s a d d e d to a s o l u t i o n m ade o f 5 ml n o r b o r n a d ie n e .
88
5 ml m e t h y l i o d i d e a n d 15 ml t e t r a h y d r o f u r a n . N i t r o g e n w a s b u b b l e d
th r o u g h t h e s o l u t i o n for s e v e r a l h o u r s , t h e n th e s o l u t i o n w a s h e a t e d to
r e f l u x for 12 h o u r s . An i n f r a r e d s p e c t r u m ( i n f ra re d s p e c t r u m 2 0 3 0 , 1 960,
1 9 4 0 , 1910 cm *) w a s t h e n t a k e n o f t h e s o l u t i o n . The t o t a l r e a c t i o n m i x ­
tu re w a s t h e n f i l t e r e d .
The r e s i d u e w a s a t a n s o l i d ( N - m e t h y l p y ri d i n iu m
i o d i d e s a l t ) . The y e l l o w f i l t r a t e w a s c o n c e n t r a t e d a n d a g a s c h r o m a t o ­
gram t a k e n , w h i c h s h o w e d no hydrocarbon, d i m e r s . The f i l t r a t e w a s ' t h e n
t a k e n to d r y n e s s a n d t h e r e s i d u e o f t h e f i l t r a t e s u b l i m e d . An in f r a r e d
s p e c t r u m (i n f r a r e d s p e c t r u m 2 0 3 0 , 19 6 0, 1 9 4 0 , 1910 cm *), n u c l e a r m a g ­
n e t i c r e s o n a n c e s p e c t r u m ( n u c l e a r m a g n e t i c r e s o n a n c e s p e c t r u m 4.42
[ 4 H ] , 3.73 [ 2 H ] , 1.30 [ 2 H ] ) , a n d a m a s s s p e c t r u m ( m a s s s p e c t r u m ,
F ig ure 16) w e r e t a k e n o f t h e y e l l o w s u b l i m e d r e s i d u e .
Therm al R e a c t i o n of D i p y r i d i n e Chromium T e t r a c a r b o n y l a n d
Norbornadiene
To 10 ml o f n o r b o r n a d i e n e , 5 ml o f m e t h y l i o d i d e a n d 15 ml of
t e t r a h y d r o f u r a n , 0.1039 g (0. 0003 mole) of d i p y r i d i n e chromiu m
t e t r a c a r b o n y l (65) w e r e a d d e d . N i t r o g e n w a s b u b b l e d t h r o u g h t h e s o l u t i o n
for s e v e r a l h o u r s a n d t h e n t h e s o l u t i o n w a s h e a t e d to r e f l u x for 12 h o u r s .
The r e a c t i o n s o l u t i o n w a s t h e n f i l t e r e d .
The r e s i d u e w a s a t a n s o l i d
( N - m e t h y l p y r i d i n i u m .i o d i d e s a l t ) . The f i l t r a t e w a s t a k e n to d r y n e s s andt h e y e l l o w s o l i d r e m a i n i n g w a s s u b l i m e d . An i n f r a r e d s p e c t r u m w a s t a k e n
(i n f r a r e d s p e c t r u m 2 0 3 0 , 19 60, 1 9 4 0 , 1908 cm *) o f t h e y e l l o w s u b l i m e d
solid.
89
I s o l a t i o n o f C a r b o n y l Po ly m er
R e a c t i o n s o f b e n z e n e , m e s i t y l e n e chromium t r i c a r b o n y l and
c hr om iu m h e x a c a r b o n y l w e r e run a s d e s c r i b e d in th e i s o l a t i o n of r e a c t i o n
i n t e r m e d i a t e s . The t o t a l r e a c t i o n p r o d u c t s w e re c o m b i n e d and" c o n c e n t
t r a t e d to l e s s t h a n 5 m l. This c o n c e n t r a t e d s o l u t i o n w a s c h r o m a t o g r a p h e d
on a c tiv a te d neutral alum ina.
H e x a n e w a s a d d e d u n t i l no more h y d r o ­
c a r b o n d i m e r s w e r e l e f t on t h e c o l u m n . The co lum n w a s t h e n w a s h e d .
w i t h 50% h e x a n e - 5 0 % b e n z e n e u n t i l a d u l l y e l l o w b a n d s t a r t e d to be
e l u t e d . Then 50% b e n z e n e a n d 50% e t h e r s o l u t i o n s w e r e a d d e d to th e
c o lu m n a n d th e d u l l y e l l o w b a n d c o l l e c t e d .
The 50% b e n z e n e , a n d 50%
e t h e r f r a c t i o n w a s c o n c e n t r a t e d to a y e l l o w v i s c o u s l i q u i d . The y e l l o w
o i l w a s r e d i s s o l v e d in 100% e t h e r a n d t h e n m e t h a n o l w a s a d d e d u n t i l a
white p re c ip ita te a p p eared .
An i n f r a r e d s p e c t r u m w a s t a k e n o f t h e d r ie d w h i t e s o l i d . The d i s ­
tin g u ish in g feature of th is infrared spectrum was a strong peak at
1715 cm \
A g a s c h r o m a to g r a m w a s t a k e n on th e F&M a n d t h e o nly p e a k
came at 1 5 8 -1 60°C.
Then a m a s s s p e c t r u m w a s t a k e n a n d i t s h o w e d t h e
w h i t e s o l i d h a d a m a s s p e a k of a t l e a s t 1 000. F i n a l l y a m e l t i n g p o i n t
w a s t a k e n a n d i t s h o w e d t h e c o m po und w a s s t a b l e to a t l e a s t 3 0 0 ° C .
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