Coordination chemistry

1. Transition Metals and Coordination
Chemistry
Chapter 23

2. Transition Metals
Similarities within a given period
and within a given group.
Last electrons added are inner electrons ( d’s, f’s).

4. 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

5. 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

10. 20_435
0.2
La
1st series (3d)
Y 2nd series (4d)
Hf 3rd series (5d)
Atomic radii (nm)
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

11. Multiple Oxidation States

12. Metallic Behavior/Reducing Strength
Lower oxidation state = more metallic

13. 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

14. Electronegativity increases down column

15. Chromium
Chemical properties reflect oxidation state

16. 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”

17. Manganese

18. Silver

19. Weak Reducing Agent, H2Q

20. Mercury

21. 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-

22. [Co(NH3)6]Cl3 [Pt(NH3)4]Br2
Complex ion remains intact upon dissolution in water

23. 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+

25. 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

28. 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

29. 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

32. Examples
K2[Co(NH3)2Cl4]
potassium diamminetetrachlorocobaltate(II)
[Co(NH3)4Cl2]Cl
tetraamminedichlorocobalt(III) chloride

35. 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

36. Structural Isomerism 1
Coordination isomerism:
Composition of the complex ion varies.
[Cr(NH3)5SO4]Br
and [Cr(NH3)5Br]SO4

37. 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

38. Linkage Isomers
[Co(NH3)5(NO2)]Cl2 [Co(NH3)5(ONO)]Cl2
Pentaamminenitrocobalt(III) Pentaamminenitritocobalt(III)
chloride chloride

39. Stereoisomerism 1
Geometric isomerism (cis-trans):
Atoms or groups arranged differently spatially
relative to metal ion
Pt(NH3)2Cl2

41. 20_444
Cl
Cl
H3N NH 3
H3N NH3
Co Co
H3N NH 3 H3N Cl
Cl NH 3
Cl Cl
Co Co
Cl
Cl
(a) (b)

42. Stereoisomerism 2
Optical isomerism:
20_446
Have opposite effects on plane-polarized light
(no superimposable mirror images)
Polarizing
filter
Tube
containing
Unpolarized
sample
light θ
Polarized
light
Rotated
polarized light

43. 20_448
Mirror image
of right hand
Left hand Right hand

45. 20_449
N
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

46. 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.

50. 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

53. 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

54. High spin Low spin

58. [V(H2O)6]2+ [V(H2O)6]3+
[Cr(NH3)6]3+ [Cr(NH3)5Cl]2+s

62. 20_459
Tetrahedral Complexes
– dz 2 dx2 – y2
– –
– –– –
– –
–
dxy dxz dyz
(a) (b)

64. 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
x
M
M z
y
(a) (b)
Approach along x-and y-axes Approach along z-axis

67. Hemoglobin & Oxyhemoglobin