Interaction mode of bridging "C2" units in dinuclear complexes of late transition metals in low oxidation states: a theoretical approach

The mode of interaction of bridging ‘C2’ units in dinuclear LmMC2MLm complexes of late transition metals in low oxidation states, for which only an acetylenic structure has been experimentally observed, has been studied. Density functional calculations were carried out on the model complexes [{MCln(CO)m-n}2(mu-C2)] (M = Cr, Mn,Fe or Co; m = 4 or 5; n=0 or 1) and allowed clarification of why only the acetylenic structure is found and most of the experimentally known compounds show a d7 configuration of the MLm metal fragment.