METATHESIS CATALYST WOCL4 PH(4)SN - THE CHEMISTRY OF RIPENING AND TRANSFORMATION TO POLYMERIZATION ACTIVE SPECIES/

Ripening of WOCl4/Ph(4)Sn binary catalyst of composition from 1 : 1 to 1 : 4 in benzene and toluene is a complex reaction in which initially homogeneous solution of the catalyst components continually changes t o a colloidal solution, and utterly to a suspension of catalytically a ctive particles consisted of lower-valent tungsten species in the solu tion of biphenyl, Ph(3)SnCl and, eventually, unreacted Ph,Sn (at compo sition 1 : 4). The yield of biphenyl is in a simple stoichiometric rel ation with the initial concentration of WOCl4 and a proof is given tha t the phenyl groups constituting biphenyl molecules come from Ph(4)Sn cocatalyst. The mechanism of the overall process is suggested. Above t wenty, mostly phenylated derivatives of phenylacetylene (PhA) and olig omers of two degrees of unsaturation were detected as by-products of P hA reaction with the ripened catalyst formed in addition to main produ ct, poly(phenylacetylene). The excess phenyls built in the oligomers a re demonstrated to come from the supplied Ph(4)Sn. The mechanism is su ggested for formation of the both oligomeric derivatives and growing c arbene centers in which oxo ligands of tungsten centers are proposed t o play a central role.