Tungsten carbonyl complexes as olefin metathesis catalysts

Abstract

Different tungsten carbonyl complexes: [W(CO) 4L 2], [NEt 4[W(CO) 4LX] and [WX 2(CO) 3L 2], where L = CH 3CN, pip, PPh 2H, PPh 3, bipy, dppe, Zr(PPh 2) 2cp 2, Zr(PPh 2C 5H 4) 2Cl 2, X = Cl −, Br −, can be transformed into catalysts for olefin metathesis in the presence of certain Group 4, 13 or 14 element halides (AX n ). The process of transformation of these systems into catalytically active complexes is a multistage one. The first stage is based upon the interaction of the tungsten complex with AX n as Lewis acid, which abstracts one ligand from the coordination sphere of tungsten, thus freeing a coordination site for the attachment of an olefin ligand. Catalytic activity of the system depends upon ligand L and X in the tungsten complex and element A in AX n . In the series of halides studied, the most active proved to be ZrCl 4, whose activity could be explained by its high Lewis acidity at the most stable metal halide bond.