New cationic palladium(II) methyl complexes and neutral palladium(II) methyl complexes chelated by a phosphine–sulfonamide ligand have been recently synthesized and fully characterized, see Chart 1. These experimental studies have shown that the neutral phosphine−sulfonamide Pd(II) complex leads to no polyethylene chain growth, while the cationic phosphine−sulfonamide Pd(II) complex is just able to dimerizes ethylene. To further understand these behaviors, reactivities of the neutral CF31 and the cationic CF31+ phosphine-sulfonamide Pd(II) complexes towards ethylene were investigated by DFT calculations.[1] DFT analyses taking into account the two possible coordination modes (O- or N-) of the sulfonamide ligand for the cationic system CF31+ suggest that the experimentally observed high activity in ethylene dimerization is the result of a facile first ethylene insertion into the O-coordinated Pd–Me isomer and a subsequent favored b-H elimination from the N-coordinated isomer formed by isomerization of the insertion product. A steric hindrance by the N-aryl substituent in the neutral systems CF31 appears to contribute significantly to a higher barrier of insertion, which accounts for the experimentally observed low activity towards ethylene oligomerization. Chart 1 REFERENCES [1] Zhongbao Jian, Laura Falivene, Philipp Wucher, Philipp Roesle, Lucia Caporaso, Luigi Cavallo, Inigo Göttker-Schnetmann, Stefan Mecking, Insights into Functional Group Tolerant Polymerization Catalysis with Phosphine–Sulfonamide Palladium(II) Complexes, Chem. Eur. J. accepted

Mechanistic insight into the etylene reactivity promoted by phosphine–sulfonamide palladium(II) complexes

249th National Meeting (2015)

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