AN APPROACH TO SEPARATION OF INDUCTIVE AND MESOMERIC EFFECTS IN COMPLEXES OF TYPES LMN(CO)5 AND LMO(CO)5

It is assumed that inductive effects operating through the ligand-metal σ bond and ligand-metal π bonding are both important in determining the carbonyl stretching force constants in LMn(CO)5 and LMo(CO)5 molecules. It is suggested that the force constants of all carbonyl groups will change by the same amount owing to the change in inductive effect in going from one ligand to another; while the differences in π bonding between two ligands will affect the tram force constant twice as much as the cis. On this basis, scales of relative σ- and π donor or acceptor character for a large number of ligands have been derived. The meaning of the σ and π parameters assigned to the ligands is discussed. © 1968, American Chemical Society. All rights reserved.