METATHESIS POLYMERIZATION OF PHENYLACETYLENE BY TUNGSTEN ARYLOXO COMPLEXES

Catalytic activity of the tungsten aryloxo complexes WCl5(OAr) and WOC l3(OAr), where Ar = 4-t-C4H9C6H4, 2,6-(t-C4H9)(2)C6H3, 2,6-Cl2C6H3, 2, 4,6-Cl3C6H2, and 2,4,6-Br3C6H2 in polymerization of phenylacetylene (2 0 degrees C, monomer to catalyst molar ratio = 1 000) was studied. The activity of WCl5(OAr) as unicomponent catalysts increases with increa sing electron withdrawing character of the -OAr ligand. Addition of tw o equivalents of organotin cocatalysts (Me(4)Sn, Bu(4)Sn, Ph(4)Sn, Bu( 3)SnH) to WCl5(O-C6H2Cl3-2,4,6) has only slight positive effect (sligh tly higher polymer yield and/or molecular weight of poly(phenylacetyle ne)s was achieved). However, in the case of WOCl3(O-C6H3Cl2-2,6) catal yst, it enhances the activity considerably by eliminating the inductio n period, Poly(phenylacetylene)s prepared with the catalysts studied h ave weight-average molecular weight ranging from 100 000 to 200 000. T hey are trans-prevailing and have relatively low molar fraction of mon omer units comprised in cyclohexadiene sequences (about 6%).