Polymeriwfion of suhstilured ace~1ene.s in Pe prestsc~ of hydrcsihes ws achiewd atalyzed by p &iri&kacarbo&ibwl~mate (0). This reactiou is e..cient not o&y for polymerization of monosubstituted acetyl~= but also for that of relatively hhiered disubstituted ac~leues to give polymer with high molecuiar weight.
Polymerization of acetylenes has been the subject of extensive investigation, from a view point of importance of polyacetylcnes as the functional materials for permeability of gases.' In recent years, several transition metals have been developed for the catalysts to polymerize acetylenes under mild conditions.;! However, the effectiveness of those transition metal catalysts was strongly depended on the structure of acetylenes, namely the kind and number of substituent groups on carbon-carbon triple bond. So the research of effective catalyst for polymerization of a variety of acetylenes with high yields and molecular weights has been of interest for many chemists in this field. Independently, we have studied hydrosilylation reactions of dienes and alkynes using Group 6 p-hydride complex catalystg; EUN[MzH(CO)io], M=Cr, MO, W, where the hydrosilylation reactions were easily took place in DME, however, we have found the reactions in toluene were resulted in the production of polyacetylenes with trace amount of hydrosilylatcd products under the same reaction conditions.
We now report on the reaction of substituted acetylenes catalyzed by p-hydridedecacarbonyldiwolframate (0) in the presence of silanes to provide polyacetylenes with high degrees of polymerization from both mono-and di-substituted alkynes.
The tungsten p-hydride catalysts used for the present reactions were prepared as follows: hexacart>onyltungsten was reduced with 2.3 cquiv. of sodium borohydride in absolute tetrahydrofuran (reflux, 3-6 h) to the sodium p-hydridedecacarbonyIdiwoKramate (A). This sodium salt was not so stable under ordinary conditions, so converted into the tetraethylammonium (B), tetrabutylphosphonium (C), tetraphenylphosphonium (D), and bis(triphenylphosphoranylidene)ammonium (E) salt by the treatment in ethanol at 0 "C overnight with Et4NBr, rt-BwPBr, PhdPBr, and (Ph3P=)zNCI, respectively.