Novel catalyst systems for the polymerization of substituted acetylenes

This article reviews two types of novel catalyst systems for the polymerization of substituted acetylenes; i.e., i) MoOCl4-based catalysts and ii) metal carbonyl-based catalysts. The MoOCl4-n-Bu4Sn-EtOH(1:1:1) catalyst achieves living polymerization of 1-chloro-1-octyne, tert-butylacetylene, and phenylacetylenes having bulky ortho substituents. The initiator efficiency for the polymerization of o-CF3-phenylacetylene reaches about 40% in anisole. Et3Al, Et2Zn, and n-BuLi also work as useful cocatalysts in the MoOCl4-based system; the polydispersity ratios of poly(o-CF3-phenylacetylene) are as small as 1.06 to 1.02. The binary MoOCl4-n-BuLi system serves without ethanol. Block copolymers of o-CF3- and o-Me3Si-phenylacetylenes can be obtained by using MoOCl4-Et3Al-EtOH(1:1:4). Whereas CCl4 is used as solvent in the polymerization of phenylacetylene by W(CO)6-CCl4-hn, only a few equivalents of Ph2CCl2 to tungsten is needed in the W(CO)6-Ph2CCl2-hn system. A tungsten complex, WCl2(CO)3-(AsPh3)2 by itself induces the polymerization of phenylacetylenes.