Molecular-orbital treatment of the relative strengths of metal–carbon bonds in substituted metal carbonyls

Abstract

Relative M–C bond orders in metal cabonyl derivatives M(CO)_nX_6–n have been determined from extended Hückel calculations. The results are in agreement with experimental determinations of M–C bond strengths; the M–C bond order increases with increasing subsitution, and CO groups trans to substituents are predicted to be more strongly bound than CO groups trans to other CO groups. The relative stabilities of geometrical isomers are correctly predicted. The theoretical basis for the conventional qualitative rationalisations of these phenomena is explored.