Tungsten phenoxides as metathesis catalysts

Dicyclopentadiene Polymerization Using Well-Characterized Tungsten Phenoxide Complexes

“…It is apparent that the activity of a particular catalyst can be empirically related to the electron-withdrawing characteristics of the phenol substituents, e.g., Hammett constants. Dodd [12,13] and Basset [14,15] report that metal electrophilicity (or olefin-philicity) is important in the olefin metathesis reaction. For the series of WOCU-jciOAr)* procatalysts prepared in this work, we are now able to gauge this electrophilicity by measuring the reduction potentials associated with each procatalyst.…”

“…, tungsten oxytetraphenoxide (WOiOCtfis)*) [10], dichlorotetrakis(phenoxide)tungsten (WCl2(OAr)4) and related complexes [8][9][10][11][12][13], Most recently, Basset and co-workers have completed a study [14] whereby treatment of tungsten hexachloride (WC16) with various substituted phenols in toluene or carbon tetrachloride leads to chlorophenoxide complexes WCl6-jc(OAr)jc, where χ = 2 to 4. These complexes are also quite active catalysts for the ringopening metathesis polymerization of strained olefins once activated by an appropriate alkylating agent, e.g., Et2AlCl [75].…”