Collect. Czech. Chem. Commun. 1994, 59, 2454-2471

Metathesis Catalyst WOCl4/Ph4Sn: The Chemistry of Ripening and Transformation to Polymerization Active Species

Jan Sedláčeka, Jiří Vohlídala, Jiří Kareša, Marta Pacovskáa and Bohumil Mácab

a Department of Physical and Macromolecular Chemistry, Charles University, 128 40 Prague 2, Czech Republic
b Department of Organic Chemistry, Charles University, 128 40 Prague 2 , Czech Republic


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.