The present study deals with the application of Rh complexes possessing a phenoxy-imine ligand (1 and 2), a beta-diiminate ligand (3 and 4), and ammonia ligands (5) as catalysts in the polymerization of substituted acetylenes (6a-h). All the catalysts (1-5) were effective for the polymerization of monosubstituted acetylenes (6a-e) and afforded polymers in moderate to high yields with high molecular weights (M-n = 15,000-93,000), and the presence of cocatalyst was not a strict requisite in the present polymerization systems in contrast to conventional [Rh(nbd)Cl](2) and [Rh(cod)Cl](2) catalysts. In the case of phenoxy-imine catalysts, the nbd-bearing one (1) was more active than the cod-bearing counterpart (2) in accordance to the general behavior of Rh catalysts, while the opposite trend was observed for beta-diiminate catalysts (3 and 4). Catalyst 2 exhibited the highest activity among all the catalysts examined in the polymerization of pherrylacetylene (6a) and afforded the highest molecular weight poly(6a) (Mn = 93,000) in almost quantitative yield. Introduction of electron-donating groups at meta and para positions of 6a (monomers 6bA) resulted in the decrease of polymer yields. Et3N and n-C4H9Li exerted cocatalytic effects when combined with 1-5 in the polymerization of 6a, resulting in the increase of both polymer molecular weight and yield. (c) 2006 Elsevier B.V. All rights reserved.