Catalytic regular polymerization of propadiene and alkylpropadienes

Abstract

Catalytic linear polymerizations of propadiene, 1,2-butadiene, and 3-methyl-1,2-butadiene were achieved with low-valent-nickel complexes as homogeneous catalysts. Interaction of propadiene with some iron, cobalt, and nickel complexes produced propadiene complexes of various stabilities. Isolated complexes involving metal-stabilized-radical-ligands were noted as the possible initiating species. Labile propadiene complexes of Ni(O) and Co(O) atoms are generally active for the catalytic polymerizations. Several factors determining the catalytic activities were discussed. The i.r. and NMR spectra revealed that the polymers obtained with the nickel catalysts are of quite regular structures. The polymer structures of asymmetrically substituted propadienes suggested that a regular propagation takes place preferentially at the unsubstituted double bond which participates in the co-ordination to metal.