New bonding modes, fluxional behavior, and reactivity in dinuclear complexes bridged by four-electron donor unsaturated hydrocarbons

New bonding modes, fluxional behavior, and reactivity in dinuclear transition metal complexes bridged by four-electron donor unsaturated hydrocarbons are discussed. The type of coordination in dinuclear systems varies while moving from one system to the other. The similarity in the dynamic behavior of these complexes are due to the migration of the bridging hydrocarbyl ligand from one atom to the other, rotation about the C-C bond, and the internal rearrangement of the dinuclear cluster. The synthesis and reactions involving the dinuclear propargyl radicals attached to fulvalne ligands are given.