Complexes of the type [(diphosphine)Cr(CO)4] (diphosphine = Ph2PN(iPr)PPh2, Ar2PN(Me)PAr2 or Ar2PCH2PAr2 (Ar = 2-C6H4(MeO)) have been synthesised. In the solid state, these complexes show tight phosphine bite angles in the range 67.82(4)° to 71.52(5)° and the nitrogen atom in N,N-bis(diarylphophino)amine ligands adopts an almost planar (sp2) geometry. All of the complexes are readily oxidised electrochemically or chemically to corresponding Cr(I) species. There is no evidence for coordination of the pendant ether group in derivatives with Ar = 2-MeO-C6H4 in either Cr(0) or Cr(I) species. Treatment of the [(diphosphine)Cr(CO)4] complexes with [NO]BF4 yields [(diphosphine)Cr(NO)(CO)3]BF4. Removal of CO ligands to generate an oligomerisation-active species is not observed with amine oxides but triethyl aluminium is effective in this role, and active catalysts can be produced. The use of weakly coordinating anions seems crucial in achieving oligomerisation catalysis.
我们合成了 [(
二膦)Cr(CO)4] 类型的配合物(
二膦 = Ph2
PN(iPr)PPh2、Ar2
PN(Me)PAr2 或 Ar2PCH2PAr2(Ar = 2-
C6H4(MeO)))。在固态下,这些配合物显示出紧密的膦咬合角,范围在 67.82(4)° 至 71.52(5)° 之间,N,N-双(二芳基膦)胺
配体中的氮原子几乎呈平面(sp2)几何形状。所有配合物都很容易被电
化学或
化学氧化成相应的 Cr(I) 物。在 Ar = 2-MeO- 的衍
生物中,没有证据表明垂醚基团在 Cr(0) 或 Cr(I) 物质中配位。用 [NO]BF4 处理[(
二膦)Cr(CO)4] 复合物可得到 [(
二膦)Cr(NO)(CO)3]BF4。胺氧化物无法通过去除 CO
配体来生成低聚活性物种,但
三乙基铝可以有效地发挥这一作用,并且可以生产出活性催化剂。使用弱配位阴离子似乎是实现低聚催化的关键。