INITIATION OF POLYMERIZATION OF PHENYLACETYLENE WITH WOCl₄ AND WCl₆ "SINGLE-COMPONENT" METATHESIS CATALYSTS

Jiøí Vohlídal¹, Jan Sedláèek¹, Marta Pacovská¹, Majda Žigon²

¹Department of Physical and Macromolecular Chemistry, Laboratory of Specialty Polymers*, Faculty of Science, Charles University, Albertov 2030, CZ-128 40 Praha 2, Czech Republic, E-mail: vohlidal@prfdec.natur.cuni.cz
²Polymer Department, National Institute of Chemistry, Hajdrihova 19, SLO-61115 Ljubljana, Slovenia

ABSTRACT

At low monomer-to-catalyst mole ratio (3:1) in benzene or toluene, phenylacetylene (PhA) re-acts with WOCl₄ to arylderivatives belonging to five homologous series with increment equal to PhA unit, low amount of chloroderivatives and traces of PhA oligomers, mainly cyclotrimers. Aryls built in the derivatives originate from the solvent used. Hydrogen transfers between PhA units were found to participate in the overall reaction. An increase in the PhA/WOCl₄ mole ratio results in a lowered yield of arylderivatives, higher yield of cyclotrimers and formation of higher PhA oligomers (ratio 12:1) or poly(phenylacetylene) (ratio 100:1). Chloroderivatives are formed in comparable amounts at any PhA/WOCl₄ mole ratio so that they can be regarded as the key by-product of reduction of WOCl₄ to low-valent tungsten species. In reaction systems with the mole ratio up to 12:1, WOCl₄ is transformed into black solid assigned to WOCl₂. It dissolves in PhA inducing its polymerization in which only PhA cyclotrimers are the side products. Formation of aryl- and chloroderivatives as well as tungsten growing species is discussed in terms of reaction pathway presuming an important role of oxo ligand of tungsten species. Reaction of PhA with WCl₆ results in a formation of various PhA chloroderivatives and a fine precipitate of reduced tungsten species, which polymerizes PhA after poorly reproducible induction period.