PYRAMIDALITY EFFECT ON METAL-METAL SINGLE BONDS

A structural database study has been made of the transition-metal comp ounds M2X8Ln with metal-metal single bonds. The existence of a pyramid ality effect in d(7)-d(7) bonds is supported by qualitative extended-H uckel molecular orbital calculations and experimental data for binucle ar rhodium compounds. The results for several families of binuclear co mplexes of Co-II, Ru-I, Os-I and Pt-III show that the metal-metal dist ance decreases with increasing pyramidality and with increasing torsio n angles. The importance of the central metal atom and of the presence of axial ligands is also discussed.