Olefin Isomerization by Iridium Pincer Catalysts. Experimental Evidence for an η<sup>3</sup>-Allyl Pathway and an Unconventional Mechanism Predicted by DFT Calculations
作者:Soumik Biswas、Zheng Huang、Yuriy Choliy、David Y. Wang、Maurice Brookhart、Karsten Krogh-Jespersen、Alan S. Goldman
DOI:10.1021/ja301464c
日期:2012.8.15
The isomerization of olefins by complexes of the pincer-ligated iridium species ((tBu)PCP)Ir ((tBu)PCP = κ(3)-C(6)H(3)-2,6-(CH(2)P(t)Bu(2))(2)) and ((tBu)POCOP)Ir ((tBu)POCOP = κ(3)-C(6)H(3)-2,6-(OP(t)Bu(2))(2)) has been investigated by computational and experimental methods. The corresponding dihydrides, (pincer)IrH(2), are known to hydrogenate olefins via initial Ir-H addition across the double bond
通过钳形连接的铱物种 ((tBu)PCP)Ir ((tBu)PCP = κ(3)-C(6)H(3)-2,6-(CH(2)P) 的复合物对烯烃进行异构化(t)Bu(2))(2)) 和 ((tBu)POCOP)Ir ((tBu)POCOP = κ(3)-C(6)H(3)-2,6-(OP(t)Bu (2))(2)) 已经通过计算和实验方法进行了研究。已知相应的二氢化物(钳形)IrH(2) 可通过双键上的初始 Ir-H 添加来氢化烯烃。这种加成也是最广泛提出的烯烃异构化机理(“氢化物加成途径”)的初始步骤;然而,动力学实验和 DFT 计算(使用 M06 和 PBE 泛函)的结果表明,在这种情况下,这不是异构化的有效途径。反而,(钳)Ir(η(2)-烯烃)物质通过形成(钳)Ir(η(3)-烯丙基)(H)中间体进行异构化;这种物质的一个例子,((tBu)POCOP)Ir(η(3)-propenyl)(