A new mechanism of metal-ligand cooperative catalysis in transfer hydrogenation of ketones
A new mechanism of metal-ligand cooperative catalysis in transfer hydrogenation of ketones
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DOI：
10.1016/j.poly.2020.114508
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发表时间：
2020-05-15
期刊：
影响因子：
2.6
通讯作者：
Williams, Travis J.
中科院分区：
文献类型：
--
作者：
Demianets, Ivan;Cherepakhin, Valeriy;Williams, Travis J.
本文报道了铱催化剂IrCl（eta（5）-Cp*）（kappa（2）-（2-吡啶基）CH_2NSO_2C_6 H_4X）（1-Me，X = CH_3和1-F，X = F）用于酮与异丙醇的转移氢化反应，该反应通过一种以前未见的金属-配体协同机理进行。在反应条件下，配合物1（1-Me和1-F）衍生为一系列催化中间体：Ir（eta（5）-CP*）（kappa（2）-（C5 H4 N）CHNSO 2Ar）（2），IrH（eta（5）-CP*）（kappa（2）-（2-吡啶基）CH 2NSO 2Ar）（3）和Ir（eta（5）-CP*）（kappa（3）-（2-吡啶基）CH 2NSO 2Ar）（4）。通过单晶X射线衍射确定了1-Me和4-Me的结构。通过动力学同位素效应、Eyring参数（Δ H不等于29.1（8）kcal mol（-1）和Δ S不等于-17（19）eu）、质子-氢化物保真度和DFT计算，提出了一个决定速率的协同氢转移步骤（2 + R2 CHOH可逆箭头3 + R2 CO）。根据密度泛函理论，一个九元环状过渡态是由一个充当质子穿梭的醇分子稳定的。(C)2020爱思唯尔有限公司版权所有。
We report iridium catalysts IrCl(eta(5)-Cp*)(kappa(2)-(2-pyridyl)CH2NSO2C6H4X) (1-Me, X = CH3 and 1-F, X = F) for transfer hydrogenation of ketones with 2-propanol that operate by a previously unseen metal-ligand cooperative mechanism. Under the reaction conditions, complexes 1 (1-Me and 1-F) derivatize to a series of catalytic intermediates: Ir(eta(5)-Cp*)(kappa(2)-(C5H4N)CHNSO2Ar) (2), IrH(eta(5)-CP*)(kappa(2)-(2-pyridyl)CH2NSO2Ar) (3), and Ir(eta(5)-CP*)(kappa(3)-(2-pyridyl)CH2NSO2Ar) (4). The structures of 1-Me and 4-Me were established by single-crystal X-ray diffraction. A rate-determining, concerted hydrogen transfer step (2 + R2CHOH reversible arrow 3 + R2CO) is suggested by kinetic isotope effects, Eyring parameters (Delta H-not equal = 29.1 (8) kcal mol(-1) and Delta S-not equal = -17(19) eu), proton-hydride fidelity, and DFT calculations. According to DFT, a nine-membered cyclic transition state is stabilized by an alcohol molecule that serves as a proton shuttle. (C) 2020 Elsevier Ltd. All rights reserved.