Question

Why does Ni not form low spin octahedral complexes?

Something to do with coordination bonding...

Answer 1

Because for a `Ni(II)` complex with octahedral coordination, the `e_g` orbitals are degenerate, and the `t_(2g)` 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 `e_g` orbitals are degenerate. A `d^8` metal centre fills the `t_(2g)` set (`6e`), and the remaining `e_g` pair of orbitals are each singly occupied. A `d^8` 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 `d^4`, `d^5`, `d^6`, and `d^7` configurations give rise to the possibility of high-spin/low-spin electronic configurations.