1. Synthesis How do I make it? Modeling How do I explain it?
Chemistry
Analysis What is this?
Synthesis How do I make it?
Three central goals
Modeling How do I explain it?

2. A Chemist’s View- How we think Three different perspectives
Macroscopic
Microscopic or
Particulate
Three different perspectives
Symbolic
NaCl

3. The Period 4 transition metals

4. Colors of representative compounds of the Period 4 transition metals
nickel(II) nitrate hexahydrate
sodium chromate
zinc sulfate heptahydrate
potassium ferricyanide
titanium oxide
scandium oxide
manganese(II) chloride tetrahydrate
copper(II) sulfate pentahydrate
vanadyl sulfate dihydrate
cobalt(II) chloride hexahydrate
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5. Aqueous oxoanions of transition elements
Mn(II)
Mn(VI)
Mn(VII)
One of the most characteristic chemical properties of these elements is the occurrence of multiple oxidation states.
V(V)
Cr(VI)
Mn(VII)
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6. Effects of the metal oxidation state and of ligand identity on color
[V(H2O)6]3+
[V(H2O)6]2+
[Cr(NH3)6]3+
[Cr(NH3)5Cl ]2+
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7. Linkage isomers

8. An artist’s wheel

10. Splitting of d-orbital energies by an octahedral field of ligands
D is the splitting energy

11. The effect of ligand on splitting energy

12. The spectrochemical series
For a given ligand, the color depends on the oxidation state of the metal ion.
For a given metal ion, the color depends on the ligand.
I- < Cl- < F- < OH- < H2O < SCN- < NH3 < en < NO2- < CN- < CO
WEAKER FIELD
STRONGER FIELD
LARGER D
SMALLER D
LONGER 
SHORTER 
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13. The color of [Ti(H2O)6]3+
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14. High-spin and low-spin complex ions of Mn2+
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15. high spin: weak-field ligand low spin: strong-field ligand
Orbital occupancy for high- and low-spin complexes of d4 through d7 metal ions
high spin: weak-field ligand
low spin: strong-field ligand
high spin: weak-field ligand
low spin: strong-field ligand
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16. What is electronic spectroscopy?
Absorption of radiation leading to electronic transitions within a molecule or complex
Absorption
Absorption
[Ru(bpy)3]2+
[Ni(H2O)6]2+
104 10
~14 000
25 000
50 000
200
400
700
visible UV UV
visible
n / cm-1 (frequency) -
l / nm (wavelength)
UV = higher energy transitions - between ligand orbitals
visible = lower energy transitions - between d-orbitals of transition metals
- between metal and ligand orbitals

17. Absorption maxima in a visible spectrum have three important characteristics
number (how many there are)
This depends on the electron configuration of the metal centre
2. position (what wavelength/energy)
This depends on the ligand field splitting parameter, Doct or Dtet and on the degree of inter-electron repulsion
intensity
This depends on the "allowedness" of the transitions which is described by two selection rules

18. [Ti(OH2)6]3+ lmax = 510 nm Do is  243 kJ mol-1 20 300 cm-1
The energy of the absorption by [Ti(OH2)6]3+ is the ligand-field splitting, Do ES ES eg eg hn Do GS GS
t2g
t2g
d-d transition
complex in electronic
Ground State (GS)
complex in electronic
excited state (ES)
[Ti(OH2)6]3+ lmax = 510 nm Do is  243 kJ mol-1
cm-1
An electron changes orbital; the ion changes energy state

19. Degenerate electronic ground state: T or E
The Jahn-Teller Distortion: Any non-linear molecule in a degenerate electronic state will undergo distortion to lower it's symmetry and lift the degeneracy
Degenerate electronic ground state: T or E
Non-degenerate ground state: A
d3 4A2g
d5 (high spin) 6A1g
d6 (low spin) 1A1g
d8 3A2g
2B1g A
2Eg
[Ti(H2O)6]3+, d1
2A1g
2T2g
n / cm-1 -
10 000
20 000
30 000

20. Limitations of ligand field theory
[Ni(OH2)6]2+ = d8 ion
3 absorption bands 2+ Ni eg A
t2g
25 000
15 000
n / cm-1 -
LFT assumes there is no inter-electron repulsion
Repulsion between electrons in d-orbitals has an effect on the energy of the whole ion

21. d2 ion
Electron-electron repulsion eg eg z2
x2-y2 z2
x2-y2
t2g
t2g xy xz yz xy xz yz
xy + z2
xz + z2 z z y y x x
lobes overlap, large electron repulsion
lobes far apart, small electron repulsion
These two electron configurations do not have the same energy

22. The Nephelauxetic Effect
cloud expanding
some covalency in M-L bonds – M and L share electrons
effective size of metal orbitals increases
electron-electron repulsion decreases
Nephelauxetic series of ligands
F- < H2O < NH3 < en < [oxalate]2- < [NCS]- < Cl- < Br- < I-
Nephelauxetic series of metal ions
Mn(II) < Ni(II) Co(II) < Mo(II) > Re (IV) < Fe(III) < Ir(III) < Co(III) < Mn(IV)

23. Transition e complexes
Selection Rules
Transition e complexes
Spin forbidden 10-3 – 1 Many d5 Oh cxs
Laporte forbidden [Mn(OH2)6]2+
Spin allowed
Laporte forbidden 1 – 10 Many Oh cxs
[Ni(OH2)6]2+
10 – 100 Some square planar cxs
[PdCl4]2-
100 – coordinate complexes of low symmetry, many square planar cxs particularly with organic ligands
Spin allowed 102 – 103 Some MLCT bands in cxs with unsaturated ligands
Laporte allowed
102 – 104 Acentric complexes with ligands such as acac, or with P donor atoms
103 – 106 Many CT bands, transitions in organic species