CHM 401

Crystal Field Theory or Ligand Field Theory

An ionic approach to understanding bonding in transition metal complexes

Consider the O_h case : what is the effect of the negative electron density from the ligands on the energies of the valence (d) orbitals

Δ_o = 10Dq = Crystal Field Splitting parameter or Ligand Field parameter

Occupation of the t_2g orbitals gives a little extra stabilization of the complex

Ligand Field Stabilization Energy (LFSE)

d electron
configuration Crystal Field
configuration LFSE number of
unpaired spins

d¹ t_2g¹ –4D_q 1

d² t_2g² –8D_q 2

d³ t_2g³ –12D_q 3

d⁴ t_2g⁴ –16D_q+ P 2 (ls)

d⁴ t_2g³e_g¹ –6D_q 4 (hs)

d⁵ t_2g⁵ –20D_q+ 2P 1 (ls)

d⁵ t_2g³e_g² 0 5 (hs)

d⁶ t_2g⁶ –24D_q+ 2P 0 (ls)

d⁶ t_2g⁴e_g² –4D_q 4 (hs)

d⁷ t_2g⁶e_g¹ –18D_q+ P 1 (ls)

d⁷ t_2g⁵e_g² –8D_q 3 (hs)

d⁸ t_2g⁶e_g² –12D_q 2

d⁹ t_2g⁶e_g³ –6D_q 1

d¹⁰ t_2g⁶e_g⁴ 0 0

P = spin pairing energy

hs = high spin

ls = low spin

d electron configuration	Crystal Field configuration	LFSE	number of unpaired spins
d¹	t_2g¹	–4D_q	1
d²	t_2g²	–8D_q	2
d³	t_2g³	–12D_q	3
d⁴	t_2g⁴	–16D_q+ P	2 (ls)
d⁴	t_2g³e_g¹	–6D_q	4 (hs)
d⁵	t_2g⁵	–20D_q+ 2P	1 (ls)
d⁵	t_2g³e_g²	0	5 (hs)
d⁶	t_2g⁶	–24D_q+ 2P	0 (ls)
d⁶	t_2g⁴e_g²	–4D_q	4 (hs)
d⁷	t_2g⁶e_g¹	–18D_q+ P	1 (ls)
d⁷	t_2g⁵e_g²	–8D_q	3 (hs)
d⁸	t_2g⁶e_g²	–12D_q	2
d⁹	t_2g⁶e_g³	–6D_q	1
d¹⁰	t_2g⁶e_g⁴	0	0