Pd-catalyzed copolymerization of methyl acrylate with carbon monoxide: Structures, properties and mechanistic aspects toward ligand design

摘要: Full details are provided for the alternating copolymerization of acrylic esters with carbon monoxide (CO) catalyzed by palladium species bearing a phosphine-sulfonate bidentate ligand. The copolymer methyl acrylate (MA) and CO had complete regioregularity stereocenters that slowly epimerize in presence methanol. In ethylene, terpolymers MA/ethylene/CO were also prepared. glass transition temperatures co- higher than ethylene/CO copolymer. Both experimental theoretical investigations performed to clarify superior nature system compared an unsuccessful conventional diphosphine system: (i) reversible insertion was directly observed isolated alkylpalladium complexes, [{o-((o-MeOC(6)H(4))(2)P)C(6)H(4)SO(3)}PdCH(CO(2)Me)CH(2)COMe], whereas it not corresponding complex 1,2-bis(diphenylphosphino)ethane (DPPE). (ii) state subsequent MA insertion, rate-determining step catalytic cycle, lower energy DPPE system. This stabilization could be attributed less hindered sulfonate moiety as well stronger back-donation from electron-deficient olefin, which is located trans sulfonate.