The expected values should be compared to the following rough guide.
For M2+ complexes, expect Δoct =
7500 - 12500 cm-1 or ν = 800 - 1350 nm.
For M3+ complexes, expect Δoct =
14000 - 25000 cm-1 or ν = 400 - 720 nm.
Δtet ~ 4/9 Δoct.
B for first-row transition metal free ions is around 1000 cm-1.
Depending on the position of the ligand in the nephelauxetic series, this
can be reduced to as low as 60% in the complex.
Extinction coefficients for octahedral complexes are expected to be around
50-100 times smaller than for tetrahedral complexes. For a typical spin-allowed
but Laporte (orbitally) forbidden transition in an octahedral complex, expect
ε < 10 m2mol-1.