BONDING AND CONFORMATIONAL ASPECTS OF THIOLATO-BRIDGED EARLY LATE HETEROBIMETALLICS

Extended Huckel and Fenske-Hall MO calculations have been used to examine the bonding a series of thiolato-bridged early-late heterobimetallics. The calculations support the postulate of a weak, dative interaction between the electron-rich late metal and the electron-deficient early metal center. Generally, for Ti species the interaction is weak sigma-bonding in character, although for Zr there is an indication of an additional pi-component. When the coordination sphere of the late metal center is trigonal or square planar, these interactions result In a MS2M' core folding and an endo-cisoid conformation of the substituents on the bridging S atoms is adopted. Alternatively, a endo-transoid conformation and a planar MS2M' core is seen when the late metal center requires a pseudotetrahedral coordination geometry. The implications of these results with respect to the structural and electrochemical properties is considered.