The successive addition of KCN and Ph3CCl to B(C6F4-C6F5-2)3 (PBB) affords triphenylmethyl salts of the [NC-PBB]− anion. By contrast, the analogous reaction with sodium dicyanamide followed by treatment with Ph3CCl leads to the zwitterionic aminoborane H2NB(C12F9)2C12F8, via nucleophilic attack on an o-F atom, together with CPh3[F-PBB]. Whereas treatment of [NC-PBB]− with either PBB or B(C6F5)3 fails to give isolable cyano-bridged diborates, the reaction of Me3SiNC-B(C6F5)3 with PBB in the presence of Ph3CCl affords [Ph3C][PBB-NC-B(C6F5)3]. Due to steric hindrance this anion is prone to borane dissociation. The longer linking group N(CN)2− gives the very voluminous anions [NCNB(C6F5)3}2]− and [N(CN-PBB)2]−. A comparison of propylene polymerisations with rac-Me2Si(Ind)2ZrMe2 activated with the various boranes or trityl borates gives an anion-dependent activity sequence, in the order [NC-PBB]− < [MeB(C6F5)3]− < [MePBB]−
≈ [PBB-NCB(C6F5)3]−
≈ [NCNB(C6F5)3}2]− < [F-PBB]−
≪ [B(C6F5)4]− < [N(CN-PBB)2]−. The anion [N(CN-PBB)2]− gives a catalyst productivity about 2500 times higher than that of [NC-PBB]− and exceeds that of [B(C6F5)4]− based catalysts. The van der Waals volumes and surface areas of the anions have been calculated and provide a rationale for the observed reactivity trends in polymerisation reactions.
将 KCN 和 Ph3CCl 相继加入 B(
C6F4-
C6F5-2)3 (PBB),可得到 [NC-PBB]- 阴离子的三苯甲基盐。与此相反,与
双氰胺钠发生类似反应,然后用 Ph3CCl 处理,通过亲核攻击邻-F 原子和 CPh3[F-PBB],可得到齐聚物
氨基
硼烷 H2NB(C12F9)2C12F8。虽然用 PBB 或 B( )3 处理 [NC-PBB]- 无法得到可分离的
氰桥二
硼酸盐,但在 Ph3CCl 的存在下,Me3SiNC-B( )3 与 PBB 反应可得到 [Ph3C][PBB-NC-B( )3]。由于立体阻碍,这种阴离子容易发生
硼烷解离。较长的连接基团 N(CN)2- 会产生体积很大的阴离子 [NCNB( )3}2]- 和 [N(CN-PBB)2]-。比较用各种
硼烷或
硼酸三甲苯酯活化的 rac-Me2Si(Ind)2ZrMe2 的
丙烯聚合反应,可以得出一个取决于阴离子的活性顺序、顺序为 [NC-PBB]- < [MeB( )3]- < [MePBB]- ≈ [PBB-NCB( )3]- ≈ [NCNB( )3}2]- < [F-PBB]-≪ [B( )4]- < [N(CN-PBB)2]-。阴离子[N(CN-PBB)2]-的催化剂生产率是[NC-PBB]-的约 2500 倍,超过了基于[B( )4]-的催化剂。阴离子的范德华体积和表面积已经计算出来,并为聚合反应中观察到的反应性趋势提供了理论依据。