Bonding preferences of C2X4-bridged bimetallic transition metal complexes of Ti, Cu, and Ag

The bonding preference of transition metal species of general formula [(PH3)(2)M](2)(mu -C2X4), where M = Cu or Ag and X = O, S, Se, or Te, and (Cp2Ti)(2)(mu -C2X4), when X = S or Se, are explored using density functional theory. The relative energies of metal binding to the bridging ligand in a dithiolene-like vs dithiocarbamate-like manner are evaluated. In all cases, the most stable structure corresponds to dithiolene-like (or side-side) bonding, consistent with the vast majority of these compounds which have been experimentally characterized. However, for M = Ag and X = S, Se, or Te, the two isomers are nearly degenerate.