Pyramidality effect on metal–metal single bonds

Abstract

A structural database study has been made of the transition-metal compounds M ₂ X ₈ L _n with metal–metal single bonds. The existence of a pyramidality effect in d ⁷ –d ⁷ bonds is supported by qualitative extended-Hückel molecular orbital calculations and experimental data for binuclear rhodium compounds. The results for several families of binuclear complexes of Co ^II , Ru ^I , Os ^I and Pt ^III show that the metal–metal distance decreases with increasing pyramidality and with increasing torsion angles. The importance of the central metal atom and of the presence of axial ligands is also discussed.