Derivation of ligand σ- and π-bonding parameters from density functional theoretical calculations and Bursten ligand additivity relationships

Abstract

New ligand additivity equations, based on the Bursten model, describing dπ orbital energies in square-planar and square–pyramidal complexes are proposed and tested for hypothetical binary Cr(0) and Mn(I) complexes of CO and CNMe. Density functional theory calculations are used to calculate the energies of dπ orbitals of binary octahedral, square–planar, and square–pyramidal d6 complexes of Mn(I) and Cr(0). Combination of the modified equations for unsaturated species with Bursten’s original equations for octahedral species allows for calculation of individual ligand bonding parameters and the separation of σ- and π-bonding effects. The calculated parameters provide interesting insight into the nature of metal–ligand bonding in the species studied. The method of separating σ- and π-bonding effects, applied here to CO and CNMe, is proposed as general method for solution of the Bursten equations for low-spin d6 octahedral systems.