User:Benjah-bmm27/degree/2/CAR

"Coordination Chemistry of the Transition Metals, Part 1"

Revision of crystal field theory, which does not explain the spectrochemical series
Ligand field theory (application of molecular orbital theory to bonding in complexes)
- e_g* orbitals are antibonding, so when occupied, metal-ligand bonds weaken and lengthen (and substitution rxns happen faster)
- Stronger metal-ligand interaction raises e_g* (and lowers e_g), while t_2g is unaffected → greater Δ_o
- Pi bonding: by symmetry, t_2g can and e_g and e_g* cannot do π bonding, π backbonding
  - π donor ligands – Δ_o ↓ (weak field ligands)
  - π acceptor ligands – Δ_o ↑ (strong field ligands)
  - good σ donors – Δ_o ↑
  - poor σ donors – Δ_o ↓
Metal ligand multiple bonds, such as imido ligands
Structural consequences of particular d electron counts
- Jahn-Teller effect: J-T theorem
  - "any non-linear molecule in a degenerate electronic ground state will undergo a geometrical distortion that removes that degeneracy"
  - for symmetry reasons, tend to get elongation of bonds along z-axis and shortening of bonds in xy plane, so in Cu²⁺, d⁹, get (d_z²)²(d_x²−y²)¹
- Planar-octahedral and planar-tetrahedral equilibria in d⁸ complexes
  - Lifschitz salts: [Ni(L-L)₂]X₂ vs. [Ni(L-L)₂X₂]
  - [NiBr₂PEtPh₂] brown, square planar, diamagnetic vs. green, tetrahedral, paramagnetic: Acta Cryst. (1992). C48, 406-408
Stability constants of complexes