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A new living and isoselective propylene polymerization precatalyst was generated via the intramolecular insertion of a ligand-appended vinyl group into the Hf-C bond of a neutral pyridylamidohafnium trimethyl complex.

The controlled polymerization of propylene with living catalysts in an isoselective fashion with high activities is a continuing challenge for catalysis, with at least one of these properties suffering in most existing systems. Through experimental and theoretical studies, the pyridylamidohafnium olefin polymerization catalysts have been optimized for living behavior, isoselectivity, and activity of propylene polymerization (Đ = 1.2, [m4] = 91%, TOF = 25 000 h–1). Substitution of the bridgehead position with geminal dimethyl substituents forces the stereoselective elements of the catalyst into closer proximity with the active site through a “buttressing effect” while simultaneously preserving symmetry in the catalyst after activation and the first monomer insertion into the Hf–Caryl bond of the ligand. Propagation was shown to be favored over termination through beta-hydrogen transfer to the monomer through a combination of theoretical modeling and experimental monitoring of the reaction which showed a linear increase in molecular weight as a function of polymer yield. Furthermore, through computational and 13C labeling NMR studies, a different mechanism of stereocontrol involving a direct ligand–monomer interaction was confirmed

[reaction: see text] Reaction of para-substituted anilines with styrene derivatives at elevated temperatures, when catalyzed by CF3SO3H, results in highly chemoselective ortho-alkylation of the aniline. When R = H, dialkylation can be achieved by varying the ratio of styrene to aniline. Several different substituted anilines and styrenes were examined, and good yields (42-87%) were obtained, except in the case where electron-withdrawing substituents are present on the styrene.

We assayed the polymerization of 1-octene in toluene-d 8 polymerized by a pyridylamidohafnium catalyst precursor activated by the cocatalyst tris(pentafluorophenyl)boron. In situ small angle neutron scattering and 1 H NMR spectroscopy were used together with time-resolved SEC to investigate the polymerization process. The catalyst system contains several polymerization active species. About 98% of the active catalyst is of uniform activity. The resulting polymers show relatively narrow molecular weight distributions. The residual catalyst exhibits an increased activity, leading to the formation of notably higher molecular weights than is generated by the majority of available active centers. With the help of NMR and SEC results the small angle neutron scattering data could be interpreted quantitatively. Good agreement was found between the expected scattering profile for nonaggregated chains and their measured counterparts. At no stage during the polymerization process could more than single polymer chains be detected.

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