The Bursten model of ligand additivity applied to orbital energetics of octahedral d6 phosphine complexes

•The Bursten Model correctly describes energetics of dπ orbitals in d6 octahedral phosphine complexes.•PF3, PCl3, PH3, PMe3, P(OMe)3 and PPh3 are ranked according to π-acceptor ability.•PF3 and PCl3 are found to be similar to CO in π-acceptor ability in Cr(0) and Mn(I) complexes.•Orbital energetics correlate with calculated structural parameters.