Facile synthesis of sterically demanding SHOP-type nickel catalysts for ethylene polymerization

摘要

The P,O-chelated shell higher olefin process (SHOP) type nickel complexes are practical homogeneous catalysts for the industrial preparation of linear low-carbon alpha-olefins from ethylene. We describes that a facile synthetic route enables the modulation of steric hindrance and electronic nature of SHOP-type nickel complexes. A series of sterically bulky SHOP-type nickel complexes with variable electronic nature, {[4-R-C6H4C(O) = C-PArPh]NiPh (PPh3); Ar = 2-[2 ',6 '-(OMe)(2)C6H3]C6H4; R = H (Ni1); R = OMe (Ni2); R = CF3 (Ni3)}, were prepared and used as single component catalysts toward ethylene polymerization without using any phosphine scavenger. These nickel catalysts exhibit high thermal stability during ethylene polymerization and result in highly crystalline linear alpha-olefinic solid polymer. The catalytic performance of the SHOP-type nickel complexes was significantly improved by introducing a bulky ortho-biphenyl group on the phosphorous atom or an electron-withdrawing trifluoromethyl on the backbone of the ligand, indicating steric and electronic effects play critical roles in SHOP-type nickel complexes catalyzed ethylene polymerization.