Transition Metals and Coordination
Chemistry
Transition Metals
Similarities within a given period
and within a given group.
Last electrons added are inner electrons (d’s, f’s).
20_431
Sc
Ti
V
Cr Mn Fe Co Ni
Y
Zr
Nb Mo Tc
La
Hf
Ta
W
Cu Zn
Ru Rh Pd Ag Cd
Re Os
Ir
Pt Au Hg
Ac Unq Unp Unh Uns Uno Une Uun Uuu
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho
Th
Pa
U
Np Pu Am Cm Bk
Cf
Er Tm Yb
Lu
Es Fm Md No
Lr
20_432
d-block transition elements
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
La*
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Ac† Unq Unp Unh Uns Uno Une Uun Uuu
f-block transition elemen ts
*Lanthanides
Ce
Pr
Nd
Pm Sm
† Actinides
Th
Pa
U
Np
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Pu Am Cm Bk
Cf
Es
Fm Md
No
Lr
20_435
0.2
La
1st series (3d)
Atomic radii (nm)
Y
2nd series (4d)
Hf
Zr
Sc
0.15
3rd series (5d)
Ta
Nb
Ti
W
Mo
Re
Tc
Os
Ru
V
Cr
Mn
Fe
0.1
Atomic number
Au
Ag
Ir
Pt
Rh
Pd
Co
Ni
Cu
Multiple Oxidation States
Metallic Behavior/Reducing Strength
Lower oxidation state = more metallic
Color and Magnetism
e- in partially filled d sublevel absorbs visible light
moves to slightly higher energy d orbital
Magnetic properties due to unpaired electrons
Electronegativity increases down column
Chromium
Chemical properties reflect oxidation state
Valence-State Electronegativity
Electronegativity, EN:
electron “pulling power”
Valence-state EN:
metal in higher oxidation state
is more positive
has stronger pull on electrons
is more electronegative
“Effective EN”
Manganese
Silver
Weak Reducing Agent, H2Q
Mercury
Coordination Compound
Consist of a complex ion and necessary counter ions
[Co(NH3)5Cl]Cl2
Complex ion:
[Co(NH3)5Cl]2+
Co3+ + 5 NH3 + Cl= 1(3+) + 5 (0) + 1(1-)
= 2+
Counter ions:
2 Cl-
[Co(NH3)6]Cl3
[Pt(NH3)4]Br2
Complex ion remains intact upon dissolution in water
Complex Ion
Species where transition metal ion is surrounded
by a certain number of ligands.
Transition metal ion:
Ligands:
Lewis acid
Lewis bases
Co(NH3)63+
Pt(NH3)3Br+
Ligands
Molecule or ion having a lone electron pair that
can be used to form a bond to a metal ion
(Lewis base).
coordinate covalent bond: metal-ligand bond
monodentate: one bond to metal ion
bidentate:
two bond to metal ion
polydentate: more than two bonds to a metal
ion possible
Formulas of Coordination Compounds
1. Cation then anion
2. Total charges must balance to zero
3. Complex ion in brackets
K2[Co(NH3)2Cl4]
[Co(NH3)4Cl2]Cl
Names of Coordination Compounds
1. Cation then anion
2. Ligands
in alphabetical order before metal ion
neutral:
molecule name*
anionic:
-ide  -o
prefix indicates number of each
3. Oxidation state of metal ion in () only if more
than one possible
4. If complex ion = anion, metal ending  -ate
Examples
K2[Co(NH3)2Cl4]
potassium diamminetetrachlorocobaltate(II)
[Co(NH3)4Cl2]Cl
tetraamminedichlorocobalt(III) chloride
20_441
Isomers
(same formula but different properties)
Structural
isomers
(different bonds)
Coordination
isomerism
Linkage
isomerism
Stereoisomers
(same bonds, different
spatial arrangements)
Geometric
(cis-trans)
isomerism
Optical
isomerism
Structural Isomerism 1
Coordination isomerism:
Composition of the complex ion varies.
[Cr(NH3)5SO4]Br
and [Cr(NH3)5Br]SO4
Structural Isomerism 2
Ligand isomerism:
Same complex ion structure but point of
attachment of at least one of the ligands differs.
[Co(NH3)4(NO2)Cl]Cl
and [Co(NH3)4(ONO)Cl]Cl
Linkage Isomers
[Co(NH3)5(NO2)]Cl2
[Co(NH3)5(ONO)]Cl2
Pentaamminenitrocobalt(III)
chloride
Pentaamminenitritocobalt(III)
chloride
Stereoisomerism 1
Geometric isomerism (cis-trans):
Atoms or groups arranged differently spatially
relative to metal ion
Pt(NH3)2Cl2
20_444
Cl
Cl
H3N
H3N
NH3
Co
Co
H3N
NH 3
NH 3
H3N
Cl
NH 3
Cl
Cl
Cl
Co
Co
Cl
Cl
(a)
(b)
Stereoisomerism 2
Optical isomerism:
20_446
Have opposite effects on plane-polarized light
(no superimposable mirror images)
Polarizing
filter
Tube
containing
sample
Unpolarized
light

Polarized
light
Rotated
polarized light
20_448
Mirror image
of right hand
Left hand
Right hand
20_449
N
N
N
Co
N
N
N
N
Mirror image
of Isomer I
N
N
N
N
Co
N
Co
N
N
Isomer I
N
N
N
Isomer II
N
20_450
Cl
N
N
Co
N
N
N
N
Co
N
Co
N
cis
N
N
N
Isomer II cannot be
superimposed exactly
on isomer I. They are
not identical structures.
Cl
Cl
Cl
N
Cl
(a)
Cl
N
Cl
trans
The trans isomer and
its mirror image are
identical. They are not
isomers of each other.
Co
Cl
N
Cl
N
N
N
N
Co
Cl
Isomer I N
Isomer II N
(b)
Isomer II has the same
structure as the mirror
image of isomer I.
Crystal Field Theory
Focus:
energies of the d orbitals
Assumptions
1. Ligands:
2. Metal-ligand bonding:
negative point charges
entirely ionic
strong-field (low-spin): large splitting of d orbitals
weak-field (high-spin): small splitting of d orbitals
20_454
eg(d z2, d x 2 – y2)

t2g (d xz, d yz, d xy)
E
 = crystal field splitting
Free metal ion
3d orbital
energies
High spin
Low spin
[V(H2O)6]2+
[V(H2O)6]3+
[Cr(NH3)6]3+
[Cr(NH3)5Cl]2+s
20_459
Tetrahedral Complexes
–
–
–
(a)
–
dz 2
–
– –– –
–
dxy
(b)
dx2 – y2
dxz
dyz
20_461
Square Planar & Linear Complexes
dx2 - y2
dz2
E
E
dxy
dz2
dxz
Free metal ion
dyz
Free metal ion
Complex
dxz
dyz
dxy
dx2 - y2
Complex
x
M
M
z
y
(a)
Approach along x-and y-axes
(b)
Approach along z-axis
Hemoglobin & Oxyhemoglobin