Transition Metal Complex Bonding and Spectroscopy Review

1. Transition Metal ComplexBonding and SpectroscopyReview

2. Bonding:Donor-Acceptor Interactions Roles of metal and ligands Making MO Diagrams for Complexes Counting d-electrons Filling in the MO Diagram High spin/Low spin cases Comparing structures for bond strength

3. Donor Acceptor MO Interactions

4. Roles: Metal d-orbitals = acceptors Ligands = donorsMO Diagram in general:

5. Specific Interactions for each d orbital based on ligand position Use Angular Overlap parameters: --for each d-orbital, add up the interactions for all the ligands -- the total for that orbital determines how much higher its energy gets

7. Example: Linear shape: ligands at positions 1 and 6dz2 dx2-y2dxydxzdyz1+1 0 0 0 0 MO Diagram:

8. Example: Square pyramid shape: ligands at positions 1, 2, 3, 4, 5dz2 dx2-y2dxydxzdyz1+4(1/4) 4(3/4) 0 0 0 MO Diagram:

9. Counting d electrons: Count over from Group 1A – size of positive chargeTi2+:V+:Co3+:

10. Filling in Electrons If gap is >=2, then need to consider high/low spin. If gap is <2, then it is always high spin. MO Diagram examples:

11. Comparing Overall Bond Order: Low spin case Square pyramid d6 case: Oh d6 case:

12. Comparing Overall Bond Order: High spin case Square pyramid d6 case: Oh d6 case:

13. Spectroscopy: 3 types of transitions 1. d-d transitions wavelength vs. bond strength 2. LMCT 3. MLCT

14. Sigma Interaction Strength

15. LMCT with Pi Donor Ligands: Mainly oxides and halides

16. MLCT with Pi Acceptor Ligands and spectroscopy: CO, CN-, pyridine