Molecular and Gold Nanoparticles
Supported N-Heterocyclic Carbene Silver(I)
Complexes – Synthesis, Characterization and
Catalytic Applications
學
生 :王趙增
指導老師 : 于淑君 博士
2009 / 07 / 20
Department of Chemistry & Biochemistry
Chung Cheng University
1
N-Heterocyclic Carbenes (NHC)
L-type two electrons
 NHCs are strongerσ-donors than the most electron rich phosphine
- less likely to dissociate from the metal during the reaction
 NHCs have come to replace phosphines in many organometallic
and organic reactions
 NHCs can be useful spectator ligands, tunable electronically and
sterically
 NHCs are most frequently prepared via deprotonation of the
corresponding azolium salts
2
N-Heterocyclic Carbenes as Ligands
- In the early 90's NHC were found to have bonding properties similar
to trialklyphosphanes( -PR3 ) and alkylphosphinates( -OP(OR)R2 ).
Herrmann, W. A.; Öfele, K; Elison, M.; Kühn, F. E.; Roesky, P. W. J. Organomet. Chem. 1994, 480, C7-C9.
- compatible with both high and low oxidation state metals
- examples:
- reaction employing NHC's as ligands:
Herrmann, W. Angew. Chem. Int. Ed. 2002, 41, 1290-1309.
3
The Applications of Ag(I) NHC
 Silver(I)-carbene complexes as carbene transfer agents
 Addition of arenes to imines
Ar
MeO
MeO
NHTs
AuCl3/AgOTf
OMe + ArCH=NTs
OMe
CH2Cl2
MeO
MeO
 Aza-Diels-Alder reaction
N
OMe
10 mol%, AgOTf
Ph
+
Ph
Ph
N
Ph
THF
Me3SiO
O
 Asymmetric aldol reaction
O
+ CNCH2SO2Tol-p
1 mol%, AgOTf
CH2Cl2
H
SO2Tol-p
O
N
 Barbier-Grignard-type reaction
O
+
H
NH2
+
I
In/AgI/ZnCl2
RT, H2O
H
N
4
The First Silver(I)-Carbene Complexes and
Carbene-Copper(I) Complexes
N
KOtBu
N
thf
N
H
N
Cl
Linear di-coordination
M+-O3SCF3
N
N
M+
thf
N
N
CF3SO3-
M = Cu, Ag
Arduengo A.J. et al. Organometallics 1993, 21, 3405-3409
5
Silver(I)-Carbene Complexes as Carbene
Transfer Agents
Wang, H. M. J. ; Lin, I. J. B. Organometallics 1998, 17, 972-975
6
Quantum Chemical Calculations for the
N-Heterocyclic Carbene Complexes
of MCl (M = Cu, Ag, Au)
The trend of the bond energies for the metal fragments is AuCl > CuCl > AgCl
Boehme, C. and Frenking, G. Organometallics 1998, 17, 5801-5809
7
Motivation
 Using NHCs ligand to replace phosphine ligand in
organomatallic catalysis.
 In comparison with other transition metals (Cu, Au), silver has
been virtually untouched as a catalyst for coupling reactions.
 To promote silver-catalyzed three-component coupling of
aldehyde, alkyne, and amine.
 Easy recovered effectivetly recycled
Immobilization of NHC-Ag(I) complexs onto Au Nanoparticles.
8
Experimental
Preparation of [Ag(hmim)2]PF6 Complex
N
Br
N
65 oC, 12h
95 % yield
Br
N
N
[Hmim]Br
PF6
KPF6
DI
o
40 C/1h
75 % yield
N
N
[Hmim]PF6
Ag2O, t-BuOK
CH2Cl2 r.t / 4 h
N
75%
N
N
PF6 Ag
N
syn-
N
N
Ag PF6
N
N
anti-
9
Experimental
Preparation of Au NPs-Ag(I)(NHC)2(PF6)
Space linker synthesis
N
N
+
Br
Br
DMF / 80oC
N
Br
N
80%
12 h
Br
1. CS(NH2)2 / ethanol
N
2. reflux , 16 hr
3. NaOH / 5 min
4. HCl /20 min
SH
+ KPF6
N
Br
75%
o
DI/40 C
1h
N
SH
N
PF6
70%
10
Experimental
Preparation of Au NPs-Ag(I)(NHC)2(PF6)
S S S
S Au S
S SS
SH
N N
N
N
Ag N
N
PF6
N
N
PF6
THF
PF6
N N
S
S
S
S Au
S
S
S
S
Ag2O, t-BuOK
S
Au S
S
S
S
PF6
N
Ag
N N
N
PF6
CH3CN
N
PF6
N
PF6
N
N
S
S Au S
S S
11
1H
NMR Spectra of [Hmim]HPF6 and
[Ag(hmim)2]PF6
2H
12
13C
N
H
C
NMR Spectra of [Hmim]HPF6 and
[Ag(hmim)2]PF6
PF6
*DMSO
N
C
*DMSO
N
N
C
Ag PF6
C
N
N
Cc
13
ESI-MS Spectrum of [Ag(hmim)2]PF6
Experimental MS Data
Calculated MS Data
N N
Ag
N N
14
IR Spectra of [Hmim]HPF6 and [Ag(hmim)2]PF6
1225 cm-1
NHC H-C-C & H-C-N bending
[Ag(hmim)2]PF6 a
(hmim)HPF6
b
1168 cm-1
4000
3500
3000
2500
2000
1500
wavenumber (cm-1)
1000
500
15
UV Spectra of [Hmim]HPF6 and
[Ag(hmim)2] PF6
3.0
π
b
[Ag(hmim)2]PF6 a
a
2.5
π* 210 nm
abs.
2.0
(hmim)2PF6
b
400
600
1.5
1.0
0.5
0.0
200
300
500
wavelength (cm-1)
700
800
16
Single-Crystal X-ray Structure of
[Ag(hmim)2]PF6
π π interaction
Dihedral Angle
1.802o(221)
bond lengths [Å]
bond angles [deg]
Ag(1)-C(1)
2.083(3)
C(2)-Ag(1)-C(11)
177.16
Ag(1)-C(11)
2.083(3)
N(1)- C(1)-N(2)
104.06
N(3)- C(11)-N(4)
104.67
17
1H, 31P,
and 19F Spextra of Au-NPsNHC Ligand
PF6
N
SH
N
-CH2SH
*DMSO
-SH
PF6
Au
31P
NMR
S
N
*
N
19F
NMR
18
Synthesis of Au NPs-Ag(I)-(NHC) Complex
N
PF6
N
H
N
S
PF6
N
N
S
S Au S
S S
S
S
N
PF6
N
Au
CH3CN
r.t./ 4h
PF6
H
N
N
H
H
N
PF6
Au
S
H
S
Au
N
S
H
N
H
H
PF6
N
H
S
Au
N
Ag PF
6
N
Ag
N
N
S
H
N
N
Ag
S
Ag2O& t-BuOK
H
Cross-link network structure
N
H
19
1H, 31P,
and 19F of Au NPs-Ag(I)-NHC Complex
H
Au
S
N
H
2H
1H
N
*DMSO
H
PF6
*
H
N
S
N
Ag
S
Au
H
N
H
31P
NMR
19F
NMR
PF6
N
20
H
1H
NMR Spectra of Ligand, Molcular and Au
Nanoparticles
*DMSO
*
*
*
21
Synthesis of Octanethiol Protected
Au-SR NPs
+
HAuCl44H2O
-
CH3(CH2)7]4N Br CH3(CH2)7SH /CHCl3
CHCl3
NaBH4 / H2O
S S S
S Au S
S SS
Particle size 2.1 ± 1.12 nm
22
TEM Image and UV Spectrum of Au
NPs-Immobilized (NHC) Ligand
230 nm Ligand centered
π
N
PF6
N
π*
1.6
S
1.4
PF6
1.2
N
N
abs.
1.0
Particle size 3.1 ± 1.3 nm
N
S
S Au S
S S
S
S
N
PF6
0.8
0.6
PF6
0.4
N
N
0.2
0.0
-0.2
200
300
400
500
600
wavelength (nm)
700
800
23
TEM Image and EDS of Au NPs-Ag(I) Complex
3.5
3.0
245 nm
2.5
Particle size: 2.1 ± 0.7 nm
abs.
S
Au S
S
S
S
2.0
N
N
Ag N
N
PF6
1.5
1.0
N
Ag
N N
N
PF6
S
S Au S
S S
0.5
0.0
200
300
400
500
600
wavelength (nm)
700
800
24
IR Spectra of Ligand & Au Nanoparticles series
HS(CH2)6-NHCPF6 (7)
Au-SR (8)
Au-IL (9)
Au-(NHC)2Ag(I)PF6 (10)
3000
2500
NHC H-C-C & H-C-N bending
1229 cm-1
2000
wavenumber (cm-1)
4000
SH stretching
3500
3000
2500
1169 cm-1
2000
1500
wavenumber (cm-1)
1000
500
25
Aldehyde, Amine, and Alkyne-coupling
Reactions (A3-Coupling)
Have attracted much attention from organic chemists for the
coupling products, propargylamines, which are major skeletons or
synthetically versatile building blocks for the preparation of many
nitrogen-containing biologically active compounds
N
Li
N
N
N
NH
O
N
O
MeO
MeO
J. Org. Chem. 1995, 60, 1590-1594
26
The First Silver-Catalyzed
Three-Component Coupling of Aldehyde,
Alkyne, and Amine
n
R -CHO +
1
2
+ R
n
1.5-3 mol% AgI
H2O, 100oC, N2
N
R2
R1
R1= aryl, alkyl n=0,1,2
Entry
Catalyst (3 mol%)
Time (h)
Conversion
(%)
1
AgOTf
14
40
2
AgBF4
14
35
3
Ag2O
14
40
4
Ag2SO4
14
42
5
AgNO3
14
40
6
AgF
14
40
7
AgBr
14
55
8
AgCl
14
60
9
AgI
14
75
Chao J. L. et. al. Org. Lett., Vol. 5, No. 23, 2003,4473-4475
27
Proposed Mechanism
for the Three –Component Coupling
2
R
Ag +
RCHO
n
H
n
N
H
N
OH
1
R
C-H
activation
n
R2
H
Ag
N
R1
R2
Chao J. L. et. al. Org. Lett., Vol. 5, No. 23, 2003,4473-4475
28
Ag(I)-Catalyzed A3-Coupling Reactions
O
+
H
Cat. 3 (3 mol%)
+
N
H
N
N2, Solvent, 100oC
Entry
Solvent, Temperature
Time
Conversion (%)a
1
Propionitrile (97oC)
1hr
91
2
Acetonitril
(83oC)
1hr
73
3
(hmim)Br
1hr
29
4
(hmim)PF6
1hr
78
5
1,4-dioxane (105 oC)
1hr
20
6
DMF
(154oC)
1hr
38
Reaction conditions: catalyst loading = 3 mol%; Benzaldehyde = 1.00 mmol; Pyperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol solvent = 1.0 mL
29
Ag(I)-Catalyzed A3-Coupling Reactions
R3-CHO
+
R2
NH
R1
Cat. 3, 1.5 ~3.0 mol%
R4
+
R2
reflux, Propionitrile
R1
N
R4
R3
Br
Alkyne
Si
O
N
H
Amine
H
N
H
N
N
H
N
H
H
N
H
N
N
H
H
O
O
O
O
H
H
H
Aldehyde
Cl
O
O
O
OMe
H
H
O
Me
H
O
Cl
H
H
30
A3-Coupling Reactions of Aliphaticaldehyde,
Amine, and Alkyne
O
+
R
H
Cat.(3) (1.5 mol%)
+
N
H
reflux, Propionitrile
O
Entry
R
H
N
R
Time (h)
Yielda (%)
0.5
93
0.5
92
0.5
95
0.5
95
0.5
93
H
1
O
O
2
H
O
3
4
H
O
H
O
5
H
H
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
31
A3-Coupling Reactions of Aromaticaldehyde,
Amine, and Alkyne
O
+
R
H
+
N
H
Cat. (3) (3 mol%)
N
reflux, propionitrile
R
R
Time (h)
Yielda (%)
H
0.5
1
2
91
95
98
2
p-OMe
0.5
1
2
2.5
35
51
65
85
3
p-Me
2
65
4
p-Cl
2
2.5
73
88
o-Cl
2
2.5
3
68
75
83
Entry
1
5
Reaction conditions: catalyst loading = 3 mol%; Benzaldehyde = 1.00 mmol; Pyperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol solvent = 1.0 mL
32
A3-Coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
R2
O
+
H
H
Entry
NH
R1
Cat.(3) (1.5 mol%)
+
R1
N R2
reflux, Propionitrile
R2
NH
R1
Time (min)
Yielda (%)
1
H
N
30
93
2
H
N
30
95
3
O
30
80
30
93
4
N
H
N
H
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
33
A3-Coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
R2
O
+
H
H
Entry
NH
R1
Cat.(3) (1.5 mol%)
+
R1
N R2
reflux, Propionitrile
R2
NH
R1
5
N
H
6
N
H
7
N
H
8
H
N
Time (min)
Yielda (%)
30
60
75
90
30
60
90
63
75
89
30
60
80
88
30
60
90
71
89
94
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
34
A3-coupling Reactions of Benzaldehyde,
Amine, and Alkyne
O
Cat. (3) 1.5 mol%
+
H
Entry
pKa
1
2
3
+
R
N
H
N
R
reflux, Propionitrile
Time (h)
Yielda (%)
19.9
0.5
92
26.5
0.5
4
12
24
0
2
6
10
0.5
4
12
10
15
18
24
R
Si
Br
Reaction conditions: catalyst loading = 3 mol%; Benzaldehyde = 1.00 mmol; Pyperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol solvent = 1.0 mL
35
Thermal v.s. Microwave Heating
microwave
thermal
Convection transition
Kappe, C. O. Angew. Chem. Int. Ed. 2004, 43, 6250-6284.
36
A3-Coupling Reactions of Aliphaticaldehyde,
Amine, and Alkyne
O
+
R
H
Cat.(3) (1.5 mol%)
+
N
H
reflux, Propionitrile
O
Entry
R
H
H
1
N
R
Time (sec)
Yielda (%)
40
89
40
95
30
85
40
92
O
O
2
H
O
3
H
O
4
H
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
37
A3-coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
R2
O
+
H
H
Entry
NH
R1
Cat.(3) (1.5 mol%)
+
R1
N R2
reflux, Propionitrile
R2
NH
R1
Time (sec)
Yielda (%)
1
H
N
20
89
2
H
N
20
92
3
O
40
90
20
93
4
N
H
N
H
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
38
A3-Coupling Reactions of para-Formaldehyde,
Amine, and Alkyne
R2
O
+
H
H
Entry
NH
R1
Cat.(3) (1.5 mol%)
+
R1
N R2
reflux, Propionitrile
R2
NH
R1
5
Time (sec)
Yielda (%)
30
90
40
85
20
80
30
83
N
H
6
N
H
7
8
N
H
H
N
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
39
A3-Coupling Reactions of Benzaldehyde,
Amine, and Alkyne
O
+
H
Entry
1
2
3
R2
Cat. (3) 3 mol% R2 N
0.5 mL (Hmim)PF6
NH +
R1
R1
Microwave, 600 w
R2
NH
R1
H
N
H
N
O
Time (sec)
Yielda (%)
60
89
60
83
60
78
N
H
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
40
Proposed Mechanism for the A3-Coupling
Reaction
H
O
H
H
N
NH
H
O
HO
OH
O
N
H
H
OH
-H2O, OH
-H2O
N
enamine ion
N
C
N
Ag
CH +
N
N
PF6
N
Ag C C
N
N
N
Cat.3
H
N
+
N
PF6
N
Ag
N
N
PF6
Cat.3
H2O
N
N
enamine ion resonance form
N
N
41
A3-Coupling Reactions Catalyzed by a
Reusable PS-supported Ag(I)-NHC complex
1.Structure indefinite
2.Quantitative NHC-Silver (I)
by ICP-Mass
24 h
42
Wang, Li. P.; Zhang, Y. L.; Wang M. Tetrahedron Letters 49 2008 6650–6654
H
N
S
N
Ag
S
Au
H
N
H
PF6
N
H
4H
2H
1,2,4,5-tetramethylbenzene
d6-DMSO
Au-[hmim]2AgPF6: 9 mg
0.25 : 0.13 = X : 0.03725
X = 0. 07164 mmol – lignad
0.07164×0.5 = 0.0358 mmol- metal center
0.0358/9 = 0.004 mol/g
Quantitative by NMR
1,2,4,5-tetramethylbenzene: 5 mg
AA analysis: 0.0038 mol/g
需時 2 天
10 min
ICP-Mass anlysis: 0.0039 mol/g
送校外
43
Reusable Au NPs-Ag(I)(NHC)2PF6
Catalyst for A3-Coupling Reaction
O
H
Cat. (10)
+
+
H
neat
N
H
Recycle
No.
Time (h)
Yield (%)
1
2
93
2
2
97
3
2
96
4
2
95
5
2
93
6
2
94
7
2
92
8
2
93
9
2
91
10
2
90
11
2
90
12
2
91
H2
C N
Reaction conditions: Catalyst loading = 20 mol%; para-formaldehyde = 1.00 mmol; pyperidine = 1.10 mmol;
phenylacetylene = 1.50 mmol propionitrile = 1.0 mL
44
Reactivity Comparision Between Au NPsAg(I)(NHC)(PF6) and [Ag(hmim)2]PF6
Cat. (3) & Cat. (10)
1.5 mol%
O
+
R
H
+
N
H
Propionitrile, reflux 97oC
O
Entry
R
H
O
1
H
H
2
O
O
3
H
O
4
N
H
R
Time
(min)
Cat. 3
Yield (%)
Cat. 10
Yield (%)
10
20
30
65
83
95
83
92
> 99
10
20
30
52
78
93
44
67
88
10
20
30
68
81
93
61
77
91
10
20
30
69
82
92
58
74
93
Reaction conditions: catalyst loading = 1.5 mol%; Benzaldehyde = 1.00 mmol; Piperidine = 1.20 mmol; Phenylacetylene
= 1.50 mmol; Propionitrile = 1.0 mL
45
Conclusions
1.The air- and water-stable catalyst [Ag(hmim)2]PF6 was
synthesized and characterized by 1H- and 13C-NMR, ESI-MS, IR,
UV, X-ray.
2.We have developed a methodology to successfully immobilize
[Ag(hmim)2]PF6 onto surfaces of Au NPs. The structure of the
supported Ag(I)-NHC complex catalyst was characterized
by 1H-NMR, IR, TEM, UV, EDS, AA, ICP-Mass.
3.Since the Au NPs- Ag(I) hybrid catalysts are highly soluble in
organic solvents, their structures and reactions were studied by
simple solution NMR technique.
4. We have successfully demonstrated the catalytic activity of
the Ag(I) complex for the three-component coupling reactions of
aldehyde, alkyne, and amine.
5. The Au NPs- Ag(I) catalyst can be quantitatively recovered and
effectively reused for many times without any loss of reactivity. 46