Changes in the interaction mode of bridging ''C-2'' units according to transition metal parameters: A theoretical approach

A simple MO model allowing the prediction of the interaction mode of bridging ''C-2'' units in dinuclear complexes has been developed. The three possible limiting structures, namely M-C= C-M, M=C=C=M, and M=C-C=M, depend on the d(n) configuration and the oxidation state of the transition metal and upon the nature of its ancillary ligands. These conclusions have been drawn on the basis of density functional calculations carried out on the model complexes [{(H2O)(n)(OH)(3-n)M}(2)(mu C-z)] (M = Ti, V, Cr, Mn; n = 0, 1, 2) where the OH- ligand mimics an OR(-) ligand, a pi-donor ligand which is widely used in organometallic chemistry. In addition, our calculations allowed the identification of two general classes of ''C-2'' bridged dinuclear transition metal complexes on the basis of the metal's parameters and position in the periodic table.