Mo2(MeCN)8][BF4]4 supported on silica: an efficient heterogeneous catalyst for the ring-opening metathesis polymerization of norbornene

Abstract

The dimolybdenum(II,II) complex salts [Mo2(MeCN)8][BF4]4, and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2 have been supported on silica to give materials represented as [Mo2(MeCN)8][BF4]4–SiO2 and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2–SiO2, respectively. Unsupported [Mo2(MeCN)8][BF4]4, [Mo2(MeCN)8][BF4]4–SiO2, unsupported [Mo2(µ-O2CMe)2(MeCN)6][BF4]2 and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2–SiO2 were each tested as heterogeneous catalysts for the ring-opening metathesis polymerization of norbornene (bicyclo[2.2.1]hept-2-ene). In the absence of AlEtCl2 cocatalyst [Mo2(MeCN)8][BF4]4–SiO2was the only species to polymerize norbornene, and at 90°C and a reaction time of 48 h the polymerization was essentially quantitative. Species [Mo2(MeCN)8][BF4]4. [Mo2(µ-O2CMe)2(MeCN)6][BF4]2 and [Mo2(µ-O2CMe)2(MeCN)6][BF4]2–SiO2 were found to be completely inactive without AlEtCl2, even at elevated temperatures. In the presence of AlEtCl2 cocatalyst [Mo2(MeCN)8][BF4]4–SiO2 was the only material which failed to polymerize norbornene at room temperature.