Screw Sense Selective Polymerization of Achiral Isocyanides Catalysed by Optically Active Nickel(II) Complexes

Article abstract of DOI:10.1021/ja00228a035

Poly(isocyanides), (RN=C<)_n, can be prepared from isocyanides, , by the catalytic action of nickel(II) compounds.The main chain of these polymers is a rigid helix.This helical conformation results from a restricted rotation around the single bonds that connect the main-chain carbon atoms.Polymerization of achiral isocyanides generally gives a racemic mixture of left- and right-handed helices, whereas polymerization of optically active isocyanides results in helices with an excess of one screw sense.We describe a procedure for obtaining poly(isocyanides) with predominantly one screw sense, starting from an achiral monomer.A catalyst is prepared by adding an optically active amine to a tetrakis(isocyanide)nickel(II) perchlorate complex.Polymerization of various achiral isocyanides with this catalist yields optically active polymers with an enantiomeric excess up to 83percent.