Why does Ni not form low spin octahedral complexes?

Something to do with coordination bonding...

1 Answer
Feb 1, 2016

Because for a Ni(II) complex with octahedral coordination, the eg orbitals are degenerate, and the t2g orbitals must be completely filled.

Explanation:

There are some few octahedral Ni(II) complexes. When the axial and non-axial metal d orbitals are split by a ligand field, the eg orbitals are degenerate. A d8 metal centre fills the t2g set (6e), and the remaining eg pair of orbitals are each singly occupied. A d8 configuration can only fill the mtal d orbitals the 1 way: high-spin/low-spin configurations ARE NOT an option.

For an octahedral complex, only d4, d5, d6, and d7 configurations give rise to the possibility of high-spin/low-spin electronic configurations.