Rhodium(I) Complexes Bearing an Aryl‐Substituted 1,3,5‐Hexatriene Chain: Catalysts for Living Polymerization of Phenylacetylene and Potential Helical Chirality of 1,3,5‐Hexatrienes
Shiori Sakamoto, Tsuyoshi Taniguchi, Yoko Sakata, Shigehisa Akine, Tatsuya Nishimura, Katsuhiro Maeda
Abstract
Abstract Unique bench‐stable rhodium(I) complexes bearing an aryl‐substituted 1,3,5‐hexatriene chain have been synthesized by reactions of (bicyclo[2.2.1]hepta‐2,5‐diene)rhodium(I) chloride dimer ([Rh(nbd)Cl] 2 ) with aryl boronic acids and diphenylacetylenes in the presence of a 50 % aqueous solution of KOH. X‐ray crystallographic analysis of the isolated complexes indicated a square‐planar structure stabilized by a strong interaction with one of the aryl groups on the 1,3,5‐hexatriene chain, which has a helical structure. The helical chirality of the isolated rhodium complexes was confirmed to be sufficiently stable to be resolved into enantiomers by HPLC on a chiral stationary phase at room temperature. It was confirmed that the isolated rhodium complexes functioned as initiators for living polymerization of phenylacetylene to give cis ‐stereoregular poly(phenylacetylene) with a well‐controlled molecular weight.