Mechanistic Aspects of [Rh(NBD)Cl]2 Initiated Oligomerization of New Acetylenic Monomers

Publication Information:

Densmore, C.G. and P.G. Rasmussen, “Mechanistic Aspects of [Rh(nbd)Cl]2 Initiated Oligomerization of New Acetylenic Monomers”, Polymer Preprints, Vol. 45(2), pp. 744-745, 2004.

Year: 2004

Although a number of papers report the use of rhodium-based initiators, very little has been said about the mechanism of acetylene polymerizations. Kishimoto and coworkers recently proposed an insertion mechanism for the rhodium-initiated polymerization of phenylacetylenes. The initiator consisted of the tetracoordinate rhodium complex, Rh(C{triple_bond}CCH)(nbd)(PPh) with 4-(dimethylamino)-pyidine. The product was found to be stereoregular poly(phenylacety1ene) with a cis-transoidal backbone microstructure. Gorman and coworkers found palladium and nickel-based catalysts to be successful in the polymerization of cyanoacetylene. Zhan and Yang addressed the polymerization mechanism of acetylenes using palladium and nickel acetylide catalysts. They propose that the initial activation step, and also the rate-determining step, involve coordination of a nickel or palladium acetylide catalyst with an acetylene. Based on NMR and elemental analysis, we propose a more complete mechanistic picture of acetylene polymerizations, especially those with electron-withdrawing substituents.