Transition metal-mediated polymerization of isocyanides

Much interest has focused on the polymerization of isocyanide, which can be regarded as a stable N-substituted iminocarbene. Transition metal complexes have served as the most efficient and versatile initiators for the polymerization of isocyanides. This review covers a variety of studies carried out on transition metal mediated polymerization of isocyanides, from mechanistic studies to functionalized polymer synthesis. Emphasis is placed on asymmetric polymerization, which leads to the formation of optically active, rigid rod helical poly(isocyanide)s. Polymerization of 1,2-diisocyanobenzenes is also dealt with in this review. The living aromatizing polymerization provides for otherwise inaccessible poly(quinoxaline-2,3-diyl)s, which also adopt non-racemizable rigid rod helical structures. Asymmetric synthesis of poly(quinoxaline-2,3-diyl)s is achieved by screw-sense selective polymerization of 1,2-diisocyanobenzenes using chiral organopalladium complexes as initiators.