Group 4 bis(chelate) metal complexes of monoanionic bidentate [E,0-] ligands(E = 0, S): synthesis and application as α-olefin polymerization catalysts

摘要

Monoanionic bidentate phenoxy-ether [0-,0] and phenoxy-thioether [0-,S] ligands were synthesizedand used to prepare octahedral group 4 metal complexes with general formula [0-,E]2ML2 (complex 1:E= S, M = Hf, L = Bn; complex 2: E =0,M = Ti, L = NMe2; complex 3: E=S, M = Ti, L = NMe2;complex 4: E = S, M = Ti, L = Cl). Variable-temperature 1H NMR studies were performed on all thecomplexes 1-4 in the range of +20 to -70 °C. For the hafnium complex 1 a dynamic interchange of theA and A enantiomers for a C2-symmetric isomer was revealed. Eyring analysis indicated thatrearrangement of the ligands occurs via a non-dissociative mechanism. In the range of the exploredtemperatures, a broadening of the signals was observed for complexes 2-3. Finally, a reversible fluxionalprocess between several isomers was revealed for complex 4. Complexes 1-4 were tested as pre-catalystsfor ethylene and propene polymerization in combination with different activators and under variableconditions. Complex 1 was found to be inactive whereas complexes 2-4 showed moderate activities inthe polymerization of ethylene and propene. A mixture of polymers with different microstructure wasobtained in all cases, coherently with the fluxional behaviour of the pre-catalysts observed in solution.