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Highly Regioselective and Helix-Sense Selective Living Polymerization of Phenyl and Alkoxyallene Using Chiral Nickel(II) Catalysts

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journal contribution
posted on 08.01.2021, 11:46 by Li Zhou, Chong-Long Li, Run-Tan Gao, Shu-Ming Kang, Lei Xu, Xun-Hui Xu, Na Liu, Zong-Quan Wu
Facile synthesis of high optically active helical polymers from achiral monomers still remains a great challenge. In this work, two chiral Ni­(II) catalysts bearing chiral R- or S-2a ligands were facilely prepared which can efficiently initiate the living/controlled polymerization of allene monomers and afford well-defined polyallenes in high yields with controlled molecular masses (Mns) and low molecular mass distributions (Mw/Mns). The catalysts showed interesting regioselectivity on the cumulated double bonds of allene monomers, as the polymerizations were highly selective which occurred on 2,3-double bonds. Moreover, the polymerization of achiral allene monomers using chiral Ni­(II) catalysts showed remarkable helix-sense selectivity. The yielded polyallenes exhibited high optical activity due to the formation of a predominant one-handed helix as revealed by circular dichroism, UV–vis, and direct atomic force microscopy (AFM) observations as well. The predominant one-handed helicity of the generated polyallenes was solely determined by the chirality of the Ni­(II) catalysts.