Synthesis of a novel oxotungsten(VI) complex having a chelating bis(aryloxo) ligand and its catalytic behavior for ring-opening metathesis polymerization

An oxotungsten complex coordinated with O-S-O chelating bis(aryloxo) ligand , WO{S(4-Me-6-(BuC6H2O)-Bu-t)(2)}Cl-2 (1), was synthesized by the reaction of WOCl4 with 2,2'-S(4-Me-6-(BuC6H2OH)-Bu-t)(2). The structure of the compl ex 1 was determined by single-crystal X-ray analysis to have pseudo C,symme try. The catalytic behavior of 1/AlEt3 system for the ring-opening metathes is polymerization of norbornene was studied. In this catalytic system, stro ng dependencies of cis/trans selectivity on the catalyst concentration and on the polymerization temperature were observed. With increasing catalyst c oncentration and with lowering polymerization temperature, the resulting po ly(norbornene)s tend to have higher cis-regularity. Oppositely, trans-rich poly(norbornene)s were produced by the polymerization under low catalyst co ncentration and at high polymerization temperature. We propose that these o bservations might come from oxotungsten-aluminum interaction.