J. Sedlacek et al., METATHESIS CATALYST WOCL4 PH(4)SN - THE CHEMISTRY OF RIPENING AND TRANSFORMATION TO POLYMERIZATION ACTIVE SPECIES/, Collection of Czechoslovak Chemical Communications, 59(11), 1994, pp. 2454-2471
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.