Bond strengths in metal carbonyl clusters

Abstract

A new method is outlined for assigning energies to the metal–metal and metal–ligand bonds of metal carbonyl clusters M_x(CO)_y, using the lengths (d) and strengths (E) of the bonds in the metals M as a basis, and assuming E(M–M) to be proportional to [d(M–M)]^–k; applied to examples with M = Fe, Ru, Os, Co, Rh, or Ir, it suggests (a) that their metal–metal bonds are generally weaker, and their metal–ligand bonds generally stronger, than previous treatments indicated; and (b) that the strength of binding of the carbonyl ligands to a particular metal increases with the cluster nuclearity x.