Polymerization of disubstituted acetylenes by monodentate NHC-Pd catalysts†
Abstract
The combination of N-heterocyclic carbene-ligated Pd complexes with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate bearing highly weakly coordinating anions led to the formation of highly active catalysts for the polymerization of disubstituted acetylenes. The use of both carbene ligands and the weakly coordinating anions was critical to obtain high activity and great control over the polymerization process. The Pd-generated polymers showed higher molecular weight, lower solubility and higher thermal stability than the Mo-based polymers. The molecular weight of the resulting polymers can be efficiently modulated by the addition of α-olefin, which acted as a chain transfer agent in this system.