Monomer-induced switching of stereoselectivity and limitation of chain growth in the polymerization of amine-containing para-substituted phenylacetylenes by [Rh(norbornadiene)Cl]2

摘要: A series of para-substituted phenylacetylenes bearing various amine-containing pendant groups 1–4 can serve as both a monomer and cocatalyst in the polymerization catalyzed by [Rh(norbornadiene)Cl]2 alone CH2Cl2, affording polyphenylacetylenes (PPAs) with different stereoselectivities molecular weights. The 4 having long flexible group produces high weight PPAs cis-transoid configurations, similar to those obtained from coordination–insertion these monomers using [Rh(norbornadiene)Cl]2/cocatalyst systems. However, stereospecific transformation trans-cisoid configuration growth limitation polymer chain are observed 1–3 containing short rigid groups. resulting have selectivities up 66% low metathesis mechanism is suggested, which steric repulsion between propagation originates successive 1,2-insertion Rh–carbene active species gives rational explanation for tendency chain.