MECHANISTIC STUDIES ON THE NICKEL-CATALYZED POLYMERIZATION OF ISOCYANIDES

All mechanistic aspects of nickel-mediated isocyanide polymerizations have been examined experimentally. Chain initiation has been studied by C-13{H-1} NMR at low temperature using a living polymerization system. Chain propagation has been examined by cyclic voltammetry, ESR spectroscopy, magnetic susceptibility measurements, temperature dependent kinetic studies, and substituent effect analysis. The chain-propagation studies were performed on both living and classical heterogeneous systems and were found to be invariant with respect to the type of nickel initiator used. Finally, chain-transfer reactions were studied by NMR, kinetic studies, substituent effect analyses, and chemical studies. Comprehensive mechanistic schemes have been derived from the experimental data and are presented as the most probable reaction pathways.