Scope and Mechanism of Homogeneous Tantalum/Iridium Tandem Catalytic Alkane/Alkene Upgrading using Sacrificial Hydrogen Acceptors
作者:David C. Leitch、Jay A. Labinger、John E. Bercaw
DOI:10.1021/om500231t
日期:2014.7.14
increases only modestly with temperature. In contrast, the rate of 1-hexene/n-heptane transfer hydrogenation catalyzed by t-Bu[PCP]IrH4 is inverse order in 1-hexene and increases substantially with temperature. Styrene has been investigated as an alternate sacrificial hydrogen acceptor. Styrene dimerization catalyzed by Cp*TaCl2(alkene) is considerably slower than 1-hexene dimerization. The conversion of styrene/heptane
报道了基于早期/晚期过渡金属对的用于烷烃和烯烃偶联的双均相催化剂体系的深入研究。该系统由用于烯烃二聚化的Cp * TaCl 2(烯烃)和用于烷烃/烯烃转移加氢的夹钳氢化铱组成。由于两种催化剂之间没有动力学相关的相互作用,因此串联机理可以使用两个独立的催化循环进行完整描述。烯烃二聚机理的特征在于Cp * TaCl 2(1-己烯)+ 1-己烯和Cp * TaCl 2(金属环戊烷)之间的熵预平衡差(ΔH °= −22(2)kcal / mol;Δ小号°= -16(2)eu); 因此,烯烃二聚的总速率在1-己烯中呈正序(表现出饱和动力学),并且仅随温度适度增加。相反,由t -Bu [PCP] IrH 4催化的1-己烯/正庚烷转移氢化速率在1-己烯中是反序的,并且随着温度的升高而增加。已经研究了苯乙烯作为替代的牺牲氢受体。Cp * TaCl 2催化苯乙烯二聚(烯烃)比1-己烯二聚反应要慢得多。通过Ta