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

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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.