High-field C-13 NMR characterization of ethene-1-C-13/propene copolymers prepared with C-s-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 C-13 NMR characterization of ethene-1-C-13/propene copolymers at low (<5 mol %) ethene content prepa red in the presence of the syndiotactic-selective ansa-metallocene catalyst (Me)(Ph)C(cyclopentadienyl)(9-fluorenyl)ZrCl2 (cocatalyst, MAO). In partic ular, from the fine structure of the resonances of the ethene-1-C-13 units we conclude that the enantioselectivity of 1,2-propene insertion is substan tially lower and the probability of chain back-skip substantially higher af ter an ethene insertion than after a propene one. Moreover, we find that th e regioirregular 2,1-propene units (whose concentration is higher than clai med in the literature) are also substantially stereoirregular.