Directly Observed <i>β</i>-H Elimination of Unsaturated PCP-Based Rhodium(III)−Alkyl Complexes
作者:Milko E. van der Boom、Catherine L. Higgitt、David Milstein
DOI:10.1021/om990073v
日期:1999.6.1
mechanism of this process has been studied by NMR, using 13C and deuterium labeling of the alkyl ligand (L = Et-d5, 13CH2CH3). 13C labeling shows that the β-H elimination is irreversible. A deuterium isotope effect of kEt/kEt-d5 = 1.4 and a rate order of Et < nPr ≪ iPr were observed. The overall process follows first-order kinetics in the Rh(III)−alkyl complexes. The activation parameters for the thermolysis
不饱和PCP型配合物Rh(L)2,6-(CH 2 P t Bu 2)2 C 6 H 3 } X(L = Et,n Pr; X = Cl,I)配合物加热后转化为相应的Rh(III)配合物-hydride的Rh(H)2,6-(CH 2 P吨卜2)2 C ^ 6 ħ 3 } X(X =氯,I)和乙烯或丙烯,产品指示的β - H消除过程。在我镨类似物时的Rh的反应中观察到(η 1 -N 2)2,6-(CH 2 P吨在-10°C下具有i PrI的Bu 2)2 C 6 H 3 },并在室温下容易分解,得到Rh(H)2,6-(CH 2 P t Bu 2)2 C 6 H 3 } I和丙烯。缺乏β-氢的类似烷基络合物在所应用的反应条件下是稳定的。这种过程的机制进行了研究通过NMR,使用13 C和烷基配体的氘标记(L = ET- d 5,13 CH 2 CH 3)。13 C标记显示β- H的消除是不可逆的。观察到氘同位素效应k