Demianets Ivan, Cherepakhin Valeriy, Maertens Alexander, Lauridsen Paul J, Sharada Shaama Mallikarjun, Williams Travis J
Donald P. and Katherine B. Loker Hydrocarbon Institute and Department of Chemistry, University of Southern California, Los Angeles, California, 90089-1661, United States.
Department of Chemistry, University of Southern California, Los Angeles, California, 90089, United States.
Polyhedron. 2020 May 15;182. doi: 10.1016/j.poly.2020.114508. Epub 2020 Mar 12.
We report iridium catalysts IrCl(η-Cp*)(κ-(2-pyridyl)CHNSOCHX) (, X = CH and , 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 ( and ) derivatize to a series of catalytic intermediates: Ir(η-Cp*)(κ-(CHN)CHNSOAr) (), IrH(ηCp*)(κ-(2-pyridyl)CHNSOAr) (), and Ir(η-Cp*)(κ-(2-pyridyl)CHNSOAr) (). The structures of and were established by single-crystal X-ray diffraction. A rate-determining, concerted hydrogen transfer step ( + RCHOH ⇄ + RCO) is suggested by kinetic isotope effects, Eyring parameters (Δ = 29.1(8) kcal mol and Δ = -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.
我们报道了用于酮与2-丙醇转移氢化反应的铱催化剂IrCl(η-Cp*)(κ-(2-吡啶基)CHNSOCHX)（X = CH和X = F），其通过一种前所未见的金属-配体协同机制起作用。在反应条件下，配合物（和）衍生出一系列催化中间体：Ir(η-Cp*)(κ-(CHN)CHNSOAr)（）、IrH(ηCp*)(κ-(2-吡啶基)CHNSOAr)（）和Ir(η-Cp*)(κ-(2-吡啶基)CHNSOAr)（）。和的结构通过单晶X射线衍射确定。动力学同位素效应、艾林参数（Δ = 29.1(8) kcal mol和Δ = -17(19) eu）、质子-氢化物保真度和密度泛函理论计算表明，存在一个速率决定的协同氢转移步骤（ + RCHOH ⇄ + RCO）。根据密度泛函理论，一个九元环状过渡态通过作为质子穿梭体的醇分子得以稳定。
