Ab initio calculation of the electronic structure of the Ni(CN)4 ion

The electronic structure of the ion Ni(CN)₄²⁻ in its ground and first excited states is described by an ab initio SCF MO calculation. Formation of the complex in its ground state implies a large charge transfer corresponding to σ-bonding, but only a very small charge transfer due to π back-donation. The transitions of lowest energy are found to be d-d transitions which would appear as rather unfavourable on the basis of orbital energy considerations.