Tunable “In-Chain” and “At the End of the Branches” Methyl Acrylate Incorporation in the Polyolefin Skeleton through Pd(II) Catalysis

The synthesis of functionalized polyolefins through coordination–insertion polymerization is a highly challenging reaction. ideal catalyst, in addition to showing high productivity, has be able control the copolymer microstructure and, particular, way polar vinyl monomer incorporation. In this contribution, we modified typical Brookhart’s catalyst by introducing fourth coordination site palladium hemilabile, potentially bidentate ligand, such as thiophenimine (N–S). obtained cationic Pd(II) complexes, [Pd(Me)(N–N)(N–S)][PF6], generated active catalysts for ethylene/methyl acrylate (MA) copolymerization leading desired with different incorporation depending on both reaction medium and N–S ligand. Surprisingly enough, produced copolymers have inserted at end branches (T(MA)) main chain (M(MA)) ratio M(MA)/T(MA) that goes from 9:91 45:55 moving dichloromethane trifluoroethanol (TFE) solvent catalysis varying catalytic behavior new complexes was compared parent compound [Pd(Me)(N–N)(MeCN)][PF6], highlighting fact when carried out trifluoroethanol, complex also produce E/MA MA branches. Accurate NMR studies reactivity precatalyst [Pd(Me)(N–N)(MeCN)][PF6] two comonomers allowed us discover fluorinated solvent, resting state an open-chain intermediate having organic fragment, originated migratory insertion into Pd–Me bond, acetonitrile coordinated not six-membered palladacycle typically observed Pd-?-diimine catalysts. This discovery supported DFT calculations situ [Pd(Me)(N–N)(N–S)][PF6] point remains sphere during catalysis. responsible growth chain.