Mechanism for Reduction Catalysis by Metal Oxo: Hydrosilation of Organic Carbonyl Groups Catalyzed by a Rhenium(V) Oxo Complex
作者:Elon A. Ison、Evan R. Trivedi、Rex A. Corbin、Mahdi M. Abu-Omar
DOI:10.1021/ja055704t
日期:2005.11.1
evaluated. Complex 3 was found to be less hydridic than Et3SiH, refuting its participation in catalysis. A viable mechanism that is consistent with experimental findings, rate measurements, and kinetic isotope effects (Et3SiH/Et3SiD = 1.3 and benzaldehyde-H/benzaldehyde-D = 1.0) is proposed. Organosilane is activated via eta2-coordination to rhenium, and the organic carbonyl adds across the coordinated Si-H
铼氧配合物 [Re(O)(hoz)2][TFPB], 1(其中 hoz = 2-(2'-羟基苯基)-2-恶唑啉(-)和 TFPB = 四(五氟苯基)硼酸盐)催化硅氢化醛和酮在环境温度和气氛下。主要的有机产品是被保护的醇,如甲硅烷基醚。分离产率范围为 86% 至 57%。该反应需要较低的催化剂负载量 (0.1 mol%),并且在 CH2Cl2 以及无溶剂的纯净状态下顺利进行。在后一种情况下,催化剂在反应结束时沉淀,便于分离和催化剂回收。制备了 Re(O)(hoz)(H), 3,并对其参与离子氢化硅烷化机制进行了评估。发现配合物 3 的氢化能力低于 Et3SiH,驳斥了其参与催化。一种与实验结果一致的可行机制,速率测量和动力学同位素效应(Et3SiH/Et3SiD = 1.3 和苯甲醛-H/苯甲醛-D = 1.0)被提出。有机硅烷通过与铼的 eta2 配位活化,有机羰基通过配位的 Si-H 键