[NiBr(σ-C6F5)(PPh3)2] and [NiCl(σ-C6Cl5)(PPh3)2] are active for ethylene dimerization in the presence of AgClO4. The activity increases with increase in the amount of AgClO4 and reaches maximum at AgClO4/Ni-complex=2. Addition of excess AgClO4 leads to marked decrease in activity with [NiBr(σ-C6F5)(PPh3)2] but a little decrease with [NiCl(σ-C6Cl5)(PPh3)2]. 31P NMR spectra of the active solution showed new resonance peaks due to [Ni(ClO4)(σ-C6X′5)(PPh3)2] and [Ni(ClO4)(σ-C6X′5)(PPh3)] (X′=F,Cl), accompanying formation of AgX (X=Br,Cl) and [Ag(ClO4)(PPh3)]. Thus the role of AgClO4 is to abstract halide anion and/or triphenylphosphine. The amount of Ni(ClO4)(σ-C6X′5)(PPh3)] is in good correlation with the rate of dimerization, which suggests this species to be catalytically active.
[NiBr(σ-
C6F5)(PPh3)2] 和 [NiCl(σ-C6Cl5)(PPh3)2] 在 Ag 存在下具有
乙烯二聚活性。活性随着Ag 量的增加而增加,并在Ag /Ni复合物=2时达到最大值。添加过量的 Ag 会导致 [NiBr(σ- )(PPh3)2] 的活性显着降低,但 [NiCl(σ-C6Cl5)(PPh3)2] 的活性略有降低。活性溶液的 31P NMR 谱显示出由 [Ni(
ClO4)(σ-C6X′5)(PPh3)2] 和 [Ni( )(σ-C6X′5)(PPh3)] (X′) 引起的新共振峰=F,Cl),同时形成 AgX (X=Br,Cl) 和 [Ag( )(PPh3)]。因此,Ag 的作用是提取卤化物阴离子和/或
三苯基膦。 Ni( )(σ-C6X′5)(PPh3)]的量与二聚速率有很好的相关性,这表明该物质具有催化活性。