characterized. Single-crystal X-ray analysis of 2a reveals that 1a forms a seven-membered chelate ring with the cis-disubstituted cyclohexyl ring in the expected chair conformation. Variable-temperature 31P1H} NMR studies of 2a have revealed a dynamic process that interchanges stereoisomers via conformational changes in the six-membered ring, often characteristic of cis-disubstituted cyclohexane derivatives
的C 4 -bridged
二膦顺-和反式-1,2-双(
二苯基膦)
环己烷(顺式,图1A ;反式,图1b)和内切酶,内切-2,3-双(二苯膦甲基)降
冰片烷和外,内-2, 3-双(
二苯基膦基甲基)降
冰片烷(endo,endo,1c ; exo,endo,1d)及其相应的
钯配合物[(P-P)PdCl 2 ](2a - d),[(P-P)Pd(OAc)2 ](3a - d)和[(PP)PdMeCl](PP = 1a,4a ; P = 1c,4c)并进行了表征。2a的单晶X射线分析表明,1a与预期的椅子构象中的顺式-二取代的环己基环形成了七元螯合环。2a的可变温度31 P 1 H} NMR研究显示了一个动态过程,该过程通过六元环的构象变化(通常是顺式特征)互换立体异构体-二取代的
环己烷衍
生物。与此相关联的交换活化的自由能已被确定(Δ ģ ⧧ = 48千焦耳摩尔- 1,图2a)。变温31 p 1个H}和31项P