Screw-sense-selective polymerization of isocyanides initiated by organotransition metal complexes.

The screw-sense-selective polymerization of isocyanides has been attained by the catalysis of dinuclear transition metal complex Cl(PR3)2PdC≡CPt(PR3)2Cl 2 using a block-copolymerization technique. (l)-and (d)-3-Menthoxycarbonylphenyl isocyanides are polymerized to give single-handed helical polymers 5(l)n and 5(d)n, respectively, which exhibit a large optical rotation arising from the helical chirality. Oligomer complexes, prepared from the reaction of 2 with the chiral isocyanides, effectively initiate the screw-sense selective polymerization of achiral isocyanides like 3, 5-di(propoxycarbonyl)phenyl isocyanide to produce single-handed helical polymers which preserve the screw sense of the initiators, although sterically smaller isocyanides such as 4-butyl- and 3-propoxycarbonylphenyl isocyanides are polymerized with gradual loss of the screw-sense selectivity in propagation steps. This short review focuses on the recent development of helical polymers such as poly(alkyne)s and poly(isocyanide)s which are synthesized by the catalysis of well-defined organotransition metal complexes.