High-Field 13C NMR Characterization of Ethene-1-13C/Propene Copolymers Prepared with Cs-Symmetric ansa-Metallocene Catalysts: A Deeper Insight into the Regio- and Stereoselectivity of Syndiotactic Propene Polymerization

In this paper, we report the results of a 150 MHz 13 C NMR characterization of ethene-1- 13 C/propene copolymers at low (<5 mol %) ethene content prepared in the presence of the syndiotactic-selective ansa -metallocene catalyst (Me)(Ph)C(cyclopentadienyl)(9-fluorenyl)ZrCl 2 (cocatalyst, MAO). In particular, from the fine structure of the resonances of the ethene-1- 13 C units we conclude that the enantioselectivity of 1,2-propene insertion is substantially lower and the probability of chain back-skip substantially higher after an ethene insertion than after a propene one. Moreover, we find that the regioirregular 2,1-propene units (whose concentration is higher than claimed in the literature) are also substantially stereoirregular.