An INDO MO Study on the Ground State and the Cationic States of Cyclopentadienyl Nickel Nitrosyl

Abstract

The electronic structure of cyclopentadienyl nickel nitrosyl (1) in the ground state as well as the cationic states of 1 are investigated by means of a semiempirical INDO Hamiltonian and many body perturbation theory. It is demonstrated that the nature of the NiNO coupling is largely covalent while the interaction between the 3d center and the cyclopentadienyl ligand is predominantly of ionic type. The ground state MO sequence of the Ni 3d orbitals is 4e2(3dx²-y²/3dxy) below 7e1 (3dXz/3dyz) and 15a1(3dz 2). The sequence of the ionization potentials is 8e1 (Cp - π) < 15a1<4e2<7e1. The ionization energies have been determined by means of the Green’s function formalism; the self-energy part has been calculated by a second order and a renormalized approximation. Both procedures predict the correct sequence of ionization events.