Electronic structure of the electron-poor dinuclear organometallic compounds [(CpM)(CpM ')mu-Cot (M, M ' = V, Cr, Fe, Co)

A systematic theoretical investigation of a variety of synfacial homo- and heterodinuclear organometallic compounds [(CpM)(CpM')]mu-Cot (Cot = cyclooc tatetraene; Cp = cyclopentadienyl) is presented. These compounds show, depe nding on the metals M and M', a number of remarkable and even surprising pr operties, concerning the metal-metal distances, the magnetic behavior and t he spin density distribution. Based on the results of CASSCF calculations, a so-called twinnocene model has been developed, which considers the dinucl ear systems as being composed of two separated metallocene-like subunits. T he formally nonbonding metal 3d electrons of the subunits interact or do no t interact, respectively, in a very specific and characteristic way, to for m the dimetal moieties. The model describes the electronic structure, the b onding properties and the wide range of the experimental findings for the w hole class of compounds. The strategy followed in the course of the study c an be generally recommended for the investigation of dinuclear transition m etal complexes.