1. Some Coordination Compounds of Cobalt Studied by Werner
Werner’s Data*
Traditional Total Free Modern Charge of
Formula Ions Cl Formula Complex Ion .
CoCl3 6 NH [Co(NH3)6]Cl
CoCl3 5 NH [Co(NH3)5Cl]Cl
CoCl3 4 NH [Co(NH3)4Cl2]Cl
CoCl3 3 NH [Co(NH3)3Cl3] . . .
Table (p. 1020)

2. Hybrid Orbitals and Bonding in the Octahedral [Cr(NH3)6]3+ Ion
Valence Bond Theory
Hybrid Orbitals and Bonding in the Octahedral [Cr(NH3)6]3+ Ion
Fig

3. Hybrid Orbitals and Bonding in the Square Planar [Ni(CN)4]2- Ion
Valence Bond Theory
Hybrid Orbitals and Bonding in the Square Planar [Ni(CN)4]2- Ion
Fig

4. Hybrid Orbitals and Bonding in the Tetrahedral [Zn(OH)4]2- ion
Valence Bond Theory
Hybrid Orbitals and Bonding in the Tetrahedral [Zn(OH)4]2- ion
Fig

5. Isomerism

6. Isomerism
Isomers: two compounds with the same formulas but different arrangements of atoms.
Coordination-sphere isomers and linkage isomers: have different structures (i.e. different bonds).
Geometrical isomers and optical isomers are stereoisomers (i.e. have the same bonds, but different spatial arrangements of atoms).
Structural isomers have different connectivity of atoms.
Stereoisomers have the same connectivity but different spatial arrangements of atoms.

7. Isomerism Diastereomers Enantiomers (Chiral: Non-superimposable
Mirror Images)

8. Isomerism
Structural Isomerism

9. Fig

10. Stereoisomerism

11. Fig

12. Stereoisomerism
Enantiomers are chiral: I.e. They are non-superimposable mirror images.
Enantiomers are “optical isomers.” eg. (+) and (-) carvone
Most physical and chemical properties of enantiomers are identical.
Therefore, enantiomers are very difficult to separate eg. Tartaric acid…ask Louis Pasteur.
Enzymes are catalysts that are very specific, acting on only one enantiomer.
Enantiomers can have very different physiological effects: eg. (+) and (-) carvone

13. Chirality

14. Optical Activity

15. Optical Activity (+) dextrorotatory (-) levorotatory
The mirror image of an enantiomer will rotate the plane of polarized
light by the same amount in the opposite direction. Eg (+) d-carvone +62o and (-) l-carvone -62o…. What about a 50:50 (racemic) mixture?

16. Color and Magnetism
Color of a complex depends on: (i) the metal and (ii) its oxidation state.
Pale blue [Cu(H2O)6]2+ can be converted into dark blue [Cu(NH3)6]2+ by adding NH3(aq).
A partially filled d orbital is usually required for a complex to be colored.
So, d 0 metal ions are usually colorless. Exceptions: MnO4- and CrO42-.
Colored compounds absorb visible light.
The color our eye perceives is the sum of the light not absorbed by the complex.

17. Color and Magnetism
Color

18. An Artist’s
Wheel
Fig

19. Relation Between Absorbed and Observed Colors
Absorbed Observed
Color  (nm) Color  (nm)
Violet Green-yellow
Blue Yellow
Blue-green Red
Yellow-green Violet
Yellow Dark blue
Orange Blue
Red Green
Table (p. 1027)

20. Color & Visible Spectra

21. Color& Spectra
The plot of absorbance versus wavelength is the absorption spectrum.
For example, the absorption spectrum for [Ti(H2O)6]3+ has a maximum absorption occurs at 510 nm (green and yellow).
So, the complex transmits all light except green and yellow.
Therefore, the complex appears to be purple.

22. Color and Magnetism Magnetism
Many transition metal complexes are paramagnetic (i.e. they have unpaired electrons).
There are some interesting observations. Consider a d6 metal ion:
[Co(NH3)6]3+ has no unpaired electrons, but [CoF6]3- has four unpaired electrons per ion.
We need to develop a bonding theory to account for both color and magnetism in transition metal complexes.

23. Crystal-Field Theory