Polymerization of substituted acetylenes by the Grubbs-Hoveyda Ru carbene complex

Abstract

Polymerization of various mono- and disubstituted acetylenes was investigated by using Grubbs-Hoveyda catalyst (1). Hexyl propiolate (2) and l-phenyl-2-(p-trimethylsilyl)phenylacetylene (3) polymerized in moderate yields. Bulk polymerization of 2 at [M]0/[Ru] = 100 and 80 °C for 24h afforded poly(2) having Mn = 25,500 and Mw/Mn = 2.63. This polymer possessed relatively high cis content (75%) according to NMR. Monomer 3 polymerized in bulk to yield poly(3) with Mn = 60,700, Mw/Mn = 2.22 under conditions of 80°C, 24h, [M] 0/[Ru] = 25. The Ru-based poly(3) displayed a narrower conjugation than those obtained with other catalysts. The 13C NMR spectra of this polymer in solid and solution states showed quite different signal patterns from those with conventional catalysts, suggesting a different geometric structure of main chain.