Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Ripening of WOCl₄/Ph₄Sn 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 to a colloidal solution, and utterly to a suspension of catalytically active particles consisted of lower-valent tungsten species in the solution of biphenyl, Ph₃SnCl and, eventually, unreacted Ph₄Sn (at composition 1 : 4). The yield of biphenyl is in a simple stoichiometric relation with the initial concentration of WOCl₄ and a proof is given that the phenyl groups constituting biphenyl molecules come from Ph₄Sn cocatalyst. The mechanism of the overall process is suggested. Above twenty, mostly phenylated derivatives of phenylacetylene (PhA) and oligomers of two degrees of unsaturation were detected as by-products of PhA reaction with the ripened catalyst formed in addition to main product, poly(phenylacetylene). The excess phenyls built in the oligomers are demonstrated to come from the supplied Ph₄Sn. The mechanism is suggested for formation of the both oligomeric derivatives and growing carbene centers in which oxo ligands of tungsten centers are proposed to play a central role.