Study on 2-thiophenecarbonyl chloride-quenched olefin polymerization with α-diimine nickel catalysts

The number of active centers in alpha-diimine nickel-catalyzed olefin homogeneous polymerization system is rarely studied before. A systemic study on quenching method with 2-thiophenecarbonyl chloride (TPCC) in homogeneous catalytic system is presented. Ethylene and propylene polymerizations catalyzed with homogeneous a-diimine nickel catalysts (ArN=C(An)-C(An)=NAr)NiBr2 (cat. 1, Ar=2,6-C6H3(i-Pr)(2)) and (ArN=C(C12H8) C=NAr)NiBr2 (cat. 2, Ar=2,6-C6H3(i-Pr)(2), C12H8=acenaphthene-1,8-diyl) were quenched by TPCC. The potential side reaction between TPCC and alkyl aluminumterminated polymer chain caused by chain transfer to cocatalyst under different quenching conditions was investigated. Samples were obtained with different TPCC/AlMAO molar ratios and had similar sulfur contents; a confirmation that the excess TPCC in the system did not cause obvious side reactions which could lead to place more thiophene groups to the polymer chains. Moreover, when the quenching time was in the range of 3-20 min, the sulfur contents remained stable and the value of N-pol (number of moles of polymer chains) was not obviously changed, supporting that sufficient quenching reaction had already accomplished within the first 3 min. We claimed that the side reaction could be ignored under controllable conditions. TPCC was confirmed to be an effective quenching agent in homogeneous catalytic system. The quenching method with TPCC was also established.