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 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

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Th Pa U Np Pu Am Cm Bk Cf 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 elements

*Lanthanides Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

† Actinides Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
 20_435

0.2
La
1st series (3d)
Y 2nd series (4d)
Hf 3rd series (5d)
Atomic radii (n m)

Zr
Sc Ta
Au
Nb W Ag
0.15 Re
Mo Os Pt
Ti Tc Ru Ir
V Rh Pd
Cr Fe Cu
Mn Co Ni

0.1
Atomic number
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: Lewis acid

Ligands: 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 Stereoisomers
isomers (same bonds, different
(different bonds) spatial arrangements)

Geometric
Coordination Linkage Optical
(cis-trans)
isomerism isomerism isomerism
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) Pentaamminenitritocobalt(III)
chloride 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 NH 3
H3N NH3
Co Co

H3N NH3 H3N Cl

Cl NH 3

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
Unpolarized
sample
light 
Polarized
light

Rotated
polarized light
20_448

Mirror image
of right hand
Left hand Right hand
20_449

N N
Mirror image
Co
N N of Isomer I

N
N N

N N N N
Co Co
N N N N
Isomer I Isomer II
N N
20_450

Cl The trans isomer and Cl Isomer II cannot be

its mirror image are superimposed exactly
N N identical. They are not N N on isomer I. They are
Co isomers of each other. Co not identical structures.
N N N Cl
Cl Cl Cl
Cl N
N N N Cl N N
trans Co cis Co Co
N N N N N Cl

Cl Isomer I N Isomer II N

Isomer II has the same

structure as the mirror
(a) (b) image of isomer I.
 Crystal Field Theory
Focus: energies of the d orbitals

Assumptions
1.Ligands: negative point charges
2.Metal-ligand bonding: 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)

D = 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

– dz 2 dx2 – y2
– –
– –– –
– –
–

dxy dxz dyz

(a) (b)
20_461

Square Planar & Linear Complexes

dx2 - y2
dz2

E
E dxy dxz dyz
dz2
dxy dx2 - y2
dxz dyz
Free metal ion Complex
Free metal ion Complex

M
M z
y
(a) (b)

Approach along x-and y-axes Approach along z-axis

Hemoglobin & Oxyhemoglobin