1. Hybridization vs. MO for Methane

2. Coordinate Covalent Bonds

3. Coordinate Covalent Compounds
CoCl3•6NH3 vs. CoCl3•5NH3
CoCl3•6NH3 + excess Ag+  3 moles of AgCl
CoCl3•5NH3 + excess Ag+  2 moles of AgCl
CoCl3•6NH3 = [Co(NH3)6]Cl3; [Co(NH3)6]3+; Co(III)
CoCl3•5NH3 = [Co(NH3)5Cl]Cl2; [Co(NH3)5Cl]2+; Co(III)

4. Structure of a Complex Ion

5. Coordination Compounds
Two spheres, or valences:
Primary: oxidation state (charge of metal ion)
Secondary: coordination number (number of ligands, often 2, 4, 6)
Counter ions: used to balance charge
Ligands
Neutral molecule or ion.
Lone pair that can be used to bond to the metal ion.
Different models are used to describe bonding (as always!).

6. The Localized Electron Model
The cobalt(III) ion possesses empty hybrid orbitals which can accept electrons.
The metal ion is considered a Lewis Acid.
The ligands possess lone pairs of electrons which can be donated to form coordinate covalent bonds.
The ligands are considered Lewis Bases.

7. MO Diagram (octahedral)
Orbitals with lone pairs on the ligands overlap with the metal ion orbitals.
Only sigma bonds are considered here.
The 3d is lower in energy than the 4s for transition metal ions.
For reference we have kept the d-orbital labels on this diagram.
Note the non-bonding d-orbitals.

8. MO Energy Diagram for [Co(NH3)6]3+
If ligands are “lone pairs”, with 6 lone pairs (octahedral) we always have 12 electrons from the ligands.
Thus, the number of electrons in the “d-orbital” range of the MO = the number of electrons in the metal ion.

9. MOs: What Do We Notice?

11. EDTA: Polydentate

12. Naming Rules: be familiar with them
[Cr(H2O)5Br]Br2.
Name will end with “bromide”.
Metal ion part of complex cation (+), so just use its name and charge (chromium(III) – why 3+?)
Five (penta) water (aqua) ligands: pentaaqua
One bromide ligand: bromo
pentaaquabromochromium(III) bromide
Na3[Co(CN)6].
Name will begin with “sodium”.
Metal ion part of complex anion (–), so add “ate” and charge (cobaltate(III))
sodium hexacyanocobaltate(III)

13. Isomerism: two main kinds

14. Structural Isomers: Coordination Isomerism

15. Structural Isomers: Linkage Isomerism

16. Stereo Isomers: Geometric (cis-trans)
square planar
octahedral

17. Stereo Isomers: Geometric (cis-trans)

18. Stereo Isomers: Optical
Optical activity: opposite effects on plane-polarized light. Molecules have nonsuperimposable mirror images.

19. Stereo Isomers: Optical

20. Stereo Isomers: Optical