Ch 19. d-Block Metals
DHvap (in kJ/mol) for Metals
Tm
Ba
W
Au
725°C
3410°C
1064°C
2
Tm across TM
3
Quick Review of Redox Rxns
To balance a half-reaction:
1.
2.
3.
4.
Identify and balance redox atoms
Add e as needed
Add H+ or OH- to balance charge
Add H2O as needed
Ex:
Balance HMnO4  Mn2+ in acidic soln
5e
+
HMnO4 + 7H+ 
Mn2+ + 4 H2O
Balance VO43  V2O3 in basic solution
4e + 2VO43 + 5H2O  V2O3 + 10 OH
E = 1.37V at pH = 14
4
Quick Review of Redox Rxns
Nernst relation
E = E - (0.059V / n) log Q
What is E (VO43 / V2O3) at pH = 12 ?
E = E - (0.059V / 4) log [OH]10
= E + (10) (0.059V / 4) (D pOH)
= +1.37 V + (0.148) (2)
= +1.66 V
produced)
(E increases with decr pH because OH is
5
Quick Review of Redox Rxns
Latimer diagrams
1.
Reverse direction, reverse sign
2.
n E are additive, not E
1.5
-1.18
Mn3+  Mn2+  Mn
E = (1) (1.5V) + 2(1.18V) / 3 = 0.28V
3.
E is independent of stoichiometry
6
Quick Review of Redox Rxns
e- + Fe3+ → Fe2+
E = 0.77 V
e- + Fe(OH)3 + 3H+ → Fe2+ + 3 H2O
E = E0 - 3(0.059) pH
e- + Fe(OH)3 → Fe(OH)2 + OHE = E0 - 0.059 pH
7
TM redox trends
TM Frost diagrams
at pH=0
Electronegativity increases for
TM going across the rows,
therefore elements become
more difficult to oxidize. A
different way of stating this is
that later TM elements are
stronger oxidants at a given
oxidation state.
This is shown by the
increasing upward slope for
oxidation reactions in Frost
diagrams.
8
TM Pourbaix diagrams
Pourbaix diagrams show increasing E for M/M2+ and M2+/M3+ equilibria
9
Early vs late TMs
2 e + CoO2

Co2+
E = 1.66V
2 e + TiO2+

Ti 2+
E = - 0.14V
Note that CoO2 is unstable in H2O because:
2 e + 4 H+ + CoO2
2 H2O
2 CoO2 + 4 H+


Co2+ + 2 H2O
O2 + 4 e + 4 H+
 2 Co2+ + O2 + 2 H2O
E = 1.66
E = -1.23
E = +0.43
10
TM redox trends
More valence e- going across the rows means higher oxidation states are possible,
but later TM are too electronegative to be oxidized to their group number.
3
4
5
6
7
8
9
10
11
12
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
+3
+4
+5
+6
+7
+6
+4
+2,3
+2,3
+2
Highest oxidation states
accessible in aqueous solution
11
TM redox trends
Within a triad, 2nd and 3rd row TM are usually
similar.
Example:
Group 6 = Cr, Mo, W triad
Cr3+ is v. stable, unlike Mo3+ and W3+
Cr6+ is a strong oxidizer, unlike Mo6+ and W6+
Generally can get higher ox states for 2nd and
3rd row TMs
Larger ions can have higher CN; CN = 6 is
generally the max in 1st row TM complexes,
but CN = 7-9 common for 2nd and 3rd row TM
[Cr(CN)6]3 (Oh) vs [Mo(CN)8]3 (D4d
square anti-prism)
12
Polyoxometallates
Metal atoms linked via shared ligands, usually corner or edge-shared
Td or Oh
Common for groups 5 (V Nb Ta) and 6 (Cr Mo W)
pH dependence:
high pH
Al(OH)4
VO43
MoO42
no M-O-M
decr pH,
polyoxometallates
decr chg / vol
lower pH
Al2O3 (s)
V2O5(s)
MoO3(s)
extensive M-O-M
13
Vanadates
2 H2VO4- + H+ 
H3V2O7- + H2O
metavanadate chains, (VO3)
pKa ~ 4
NaVO3
14
Polyoxometallates
decavanadate
has edge-sharing Oh
6 MoO42 + 10 H+  Mo6O192 + 5 H2O
M6O19n ; M = Nb,Ta (group 5); Mo,W (group 6)
There are 6 edge-sharing Oh, each Oh has 1 unique O
1
4 shared O
4x½
1 center O
1 x 1/6
total O / M
3 1/6 = M6O19
15
Keggin structure
[PMo12O40]3
Keggin structures
Td site at cluster center, can also be As,Si,B,Te,Ti
PO43- + 12 WO42- + 27 H+  H3PW12O40 + 12 H2O
http://en.wikipedia.org/wiki/Keggin_structure (ref Fig below)
X2M18O62n−
Dawson structure
16
Ferrodoxins
17
Clusters (M-M bonding)
“NaReCl4” is
royal blue,
diamagnetic
[Mo2(CH3CO2)4]
Mo-Mo = 2.11 Å
[Re2Cl8]2- D4h
Re-Re = 2.24 Å
< ClReRe = 104°
2 Mo(CO)6 + 4 CH3COOH

[Mo2(O2CCH3)4] + 4 H2 + 12 CO
Re(m) has Re-Re = 2.74 Å and Tm=3180°C ; Mo(m) Mo-Mo = 2.80Å
18
M-M bonding interactions
[M2X8]n common in groups 6-9 (Mo, W, Re, Ru, Rh)
19
Electronic configurations
Cluster
ions
config
b.o.
b.l.
[Mo2(SO4)4]4
Mo(II) d4
σ242
4
2.11 Å
[Mo2(SO4)4]3
Mo(II) d4
σ241
3.5
2.17 Å
Mo(III) d3
20
Electronic configurations
Cluster
ions
config
b.o. b.l.
[Mo2(HPO4)4]2
Mo(III) d3
σ24
3
2.22 Å
[Ru2Cl2(O2CCl)4] Ru(II) d6
Ru(III) d5
σ242**2 2.5 2.27 Å
21
Electronic Configurations
22
Larger Metal Clusters
[Re3Cl12]3-
D
3 Zr(s) + ZrCl4(g)  4 ZrCl (s)
ZrCl
Zr-Zr bondlengths
intrasheet 3.03 Å
Intersheet 3.42 Å
In Zr (m)
3.19 Å
23
MoCl2 and [Mo6Cl14]2[Mo6Cl14
]2-
HCl (aqu)
MoCl2
4 of the 6 Cl bridge to other Mo6
clusters
For each Mo6:
8 Cl
capping faces
4 (½ Cl)
bridging
2 Cl
unique
12 Cl / Mo6 cluster
Similar for M = Mo, W, Nb,Ta
24
Groups 8-11
Noble metals : groups 8 – 11 except Fe, Co, Ni
metallic forms can exist under environment conditions (see Pourbaix diagrams)
Group 11 metals (Cu, Ag, Au) can even exist in strong acid, for example Au
does not react with HCl (conc)
NO3 oxidant, Cl forms stable complex
Au (s)
3 HCl / 1 HNO3

[AuCl4]- (aq) + NO (g)
“aqua regia”
[Au(CN)2]- (aq)
O2 / CN
25
Group 11
+1 state = d10
no LFSE
- usually CN = 2 linear (VSEPR)
- often disproportionate
2 Cu+  Cu (s) + Cu2+
AuCl
E = +0.36 at pH = 0
1.2
- soft LA
Kf
at pH = 14
I > Br > F
R3P > R3N
S2- > O2
sometimes Td
+3 state = d8
- usually D4h square planar (ex AuCl4-)
AuF3
Ni(II)
Cu(III)
Rh(I)
Pd(II)
Ag(III)
Ir(I)
Pt(II)
Au(III)
26
Group 12 (Zn, Cd, Hg)
Not noble metals; Zn, Cd are readily oxidized
pH = 0
Fe/Fe2+
E0 =
+ 0.44V
Cu/Cu2+
E0 =
 0.34V
Zn/Zn2+
E0 =
+ 0.76V
Zn(m) is used for
anodic protection
(sacrificial anode)
www.boatzincs.com/shaft.html
Why the aperiodic change from group 11 to 12 ?
B–H approach:
Cu
Zn
M (s)  M (g)
+ 338
+131 kJ/mol
M (g)  M2+ (g) + 2 e
+2704
+2639
M (s)  M2+ (g) + 2 e
+3012
+2770
27
Group 12
Group 12 has d10s2 filled orbitals, much weaker M–M bonding, and lower IE
MP
Cu 1080°C Zn
420 C
Cd
320
Hg
- 39
Zn2+
common CN = 4 (6)
Cd2+
common CN = 6 (4)
Hg2+
common CN = 2 (linear)
Hg2+ is stable in aqu solution
HgCl – mercurous chloride (calomel) is [Hg2]2+ 2Cl
bondlengths
Raman band at 171cm1 Hg–Hg stretch
Hg (m)
300 pm
Diamagnetic (Hg+ would be d10s1)
Hg22+
250-270 pm
XRD
28
Hg catenation
Hg32+ linear ion (catenation)
SO2(l)
(6-x) Hg + 3 AsF5  2 Hg3 x/2 AsF6 + AsF3
Superconductor Tc ~ 4 K
Hg3NbF6 2D hex Hg plane
Gray = Hg, white = F, black = Nb
29
f-block elements
Relatively constant electroneg across block (shielding keeps Z* = Z-σ
nearly constant), so chemistry is very consistent across f-block
Ions – have only f valence e
Ce = [Xe]4f2 6s2
Ce3+ = [Xe]4f1
Ce4+ = [Xe]
All Ln have 3+ as their most stable oxidation state
Ce4+ is relatively stable (f)
Eu2+
“
“
“
(f7)
E0 (Ce4+/ Ce3+) = +1.76V strong oxidant
E0 (Eu2+/ Eu3+) = + 0.35V mild reductant
30
Actinide
Frost
Diagrams
31
Pourbaix fblock
32
Ligand interactions
f-block metal – ligand interactions:
Ligands have less influence on f orbitals
f–f electronic transitions are sharp, relatively independent of
ligand type, and long-lived (slow non-radiative energy
transfer)  luminescence
d–d transition forbidden
(Laporte selection rules)
Eu(III) 1 % gives bright
orange-red luminescence
Gd2O2S: Pr
Gd(III) = f7 colorless (spin forbidden
transitions)
Pr(III) = f2 green
33
Actinides
actinides +3 oxidation state common, but high ox states also:
Th4+
(f);
U3+
U6+
all common
ThO2
ArO22+ linear cation for U, Np, Pu, Am
UO22+ uranyl cation (bright yellow)
High CN common (8-10)
ThCl4
[UO2(NO3)2(OH2)4]
34