Structure and reactivity of tungsten(II) and molybdenum(II) compounds containing an MM′ bond

The synthesis of heterobimetallic WSn, WGe, MoSn, and MoGe seven-coordinate chlorocarbonyl complexes of the type: [(CO)4M(μ-Cl)3M(M′Cl3)(CO)3], [MCl(M′Cl3)(CO)3(NCR)2], [M(M′Cl3)(CO)3(η2,η2-C7H8)] (M = W, Mo; M′ = Sn, Ge) is described. The crystal structures of these compounds together with their spectroscopic characteristics in solution are discussed. The reactivity and catalytic activity of these compounds in reactions with alkenes and alkynes is also reviewed. Special attention is given to catalytic reactions that lead to the formation of new carbon–carbon bonds such as polymerization of terminal alkynes, metathesis, and ring-opening metathesis polymerization of cyclic olefins (ROMP).