five-membered-ring nickel chelate, and an anionic N-donor moiety. Complexes 5a,b are active, but short-lived, ethylene polymerization catalysts with turnover numbers in excess of 60 000 mol ethylene/mol catalyst. Polymer branching is controlled by variation of temperature and pressure. A correlation between ethylene pressure and polymer molecular weight suggests that chain transfer occurs by a β-hydride elimination
报道了制备2-
苯胺基过
萘醌的一般合成路线。2-(
2,6-二甲基苯胺基)
哌啶酮(4a)和2-(
2,6-二异丙基苯胺基)
哌啶酮(4b)用作相应的中性
镍(II)配合物[[((2,6-Me 2 C 6 H 3)NC 13 H 7 O] Ni(Ph)(PPh 3)](5a)和[[(2,6- i Pr 2 C 6 H 3)NC 13 H 7 O] Ni(Ph)(PPh 3)](5b)。这些
镍配合物的关键特征是受阻的N-芳基环,五元环的
镍螯合物和阴离子的N-供体部分。络合物5a,b是活性的但寿命短的
乙烯聚合催化剂,其周转数超过60000摩尔
乙烯/摩尔催化剂。聚合物支化通过温度和压力的变化来控制。
乙烯压力和聚合物分子量之间的相关性表明,链转移是通过β-
氢化物消除途径发生的。最后,在所用的聚合条件下观察到5b分解成游离
配体。