NEt2, H) and in the cathodic isomer the electron rich aryl ring is located above the Ru=CHPh unit. This orientational effect provides clear evidence for strong pi-pi through-space interactions in the RuIII complexes, assuming that the alternative through-bond transfer of electron density is equally efficient in both isomers.
18个带有4,4'-R取代的芳基环的N-杂环卡宾(N,N'-双(
2,6-二甲基苯基)
咪唑)-2-亚烷基和各自的二
氢配体)的供电子特性使用电
化学技术研究了各自的Grubbs II配合物中的4'-R = NEt2,OMe,Me,H,SMe,F,Cl,Br,I)。4-R取代基的性质对DeltaE1 / 2 = +0.196和+0.532 V之间的RuII / III
氧化还原电势有很大的影响。4-R不等于4-R'的三种不对称Grubbs II配合物也是合成的。动态NMR光谱显示(NHC)C-Ru键(在333 K处DeltaG = 89 kJ mol(-1)周围)受限制的旋转,分别导致两种阻转异构体,其异构体比率接近于1。每种异构体,即4-R / 4-R'的两个方向 相对于R =
CHPh单元的取代的均
三环,引起不同的
氧化还原电势(4-R = NEt 2,4-R′= Br:DeltaE1 / 2 =