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首页> 外文期刊>ACS catalysis >A Bifunctional Iridium Catalyst Modified for Persistent Hydrogen Generation from Formic Acid: Understanding Deactivation via Cyclometalation of a 1,2-Diphenylethylenediamine Motif
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A Bifunctional Iridium Catalyst Modified for Persistent Hydrogen Generation from Formic Acid: Understanding Deactivation via Cyclometalation of a 1,2-Diphenylethylenediamine Motif

机译：改性甲酸持久氢气的双官能铱催化剂：了解通过1,2-二苯基乙二胺基胺的环级级级级核化的理解失活

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摘要

Thermal degradation of a bifunctional Ir complex with a 1,2-diphenylethylenediamine (DPEN) framework was investigated, which is relevant to catalyst deactivation in the acceptorless dehydrogenation of formic acid. The well-defined hydridoiridium complex 1b, derived from N-triflyl-1,2-diphenylethylenediamine (TfDPEN), proved to be solely transformed at the reflux temperature of 1,2-dimethoxyethane (DME) into two iridacycles (2 and 3) via C-H bond cleavage at the ortho carbon atoms of the phenyl substituents on the diamine backbone. These products were successfully isolated and characterized by NMR, elemental analysis, and X-ray crystallography. The iridacycle formation was significantly enhanced in the presence of water, possibly due to facile deprotonative orthometalation via a hydroxidoiridium intermediate. To prevent the deactivation process caused by the cyclometalation of the DPEN moiety, a hydridoiridium complex (5b) without phenyl substituents was synthesized from N-triflylethylenediamine (TfEN). The modified complex 513 showed a pronounced ability to catalyze hydrogen evolution from formic acid in a 1/1 mixed solvent of water and DME even in the absence of base additives. The initial rate was maintained for a longer time relative to 1b, and thus formic acid was mostly converted within 80 min under the conditions of a HCOOH/5b ratio of 15900 at 60 degrees C.
机译：研究了与1,2-二苯基乙二胺（DPEN）框架的双官能红外络合物的热降解，与甲酸的无催化剂脱氢中的催化剂失活相关。衍生自N-Triflyl-1,2-二苯基乙二胺（TFDPEN）的明确定义的氢化氢吡啶络合物1B，证明在1,2-二甲氧基乙烷（DME）的回流温度下仅转化为两个虹吸脉（2和3） Ch键在二胺骨架上苯基取代基的邻碳原子的粘合。通过NMR，元素分析和X射线晶体成功分离出这些产品。在水的情况下，铱形成显着增强，可能是由于通过羟基氧化亚中间体的脱助性矫形镜管。为了防止由DPEN部分的环荷化引起的失活过程，从N-三甲丁乙二胺（TFEN）合成了没有苯基取代基的氢化氢吡啶络合物（5B）。改性复合物513表明，即使在没有碱性添加剂的情况下，也表明了催化水和DME的1/1混合溶剂中的甲酸中的氢化氢化的能力。相对于1b保持较长时间的初始速率，因此在60℃下的HCOOH / 5B比的HCOOH / 5B比的条件下，甲酸在80分钟内大多在80分钟内转化。

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