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Mechanism of Chemical and Electrochemical N2 Splitting by a Rhenium Pincer Complex
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-06-01 , DOI: 10.1021/jacs.8b03755
Brian M Lindley 1 , Richt S van Alten 2 , Markus Finger 2 , Florian Schendzielorz 2 , Christian Würtele 2 , Alexander J M Miller 1 , Inke Siewert 2, 3 , Sven Schneider 2, 3
Affiliation  

A comprehensive mechanistic study of N2 activation and splitting into terminal nitride ligands upon reduction of the rhenium dichloride complex [ReCl2(PNP)] is presented (PNP– = N(CH2CH2PtBu2)2–). Low-temperature studies using chemical reductants enabled full characterization of the N2-bridged intermediate [{(PNP)ClRe}2(N2)] and kinetic analysis of the N–N bond scission process. Controlled potential electrolysis at room temperature also resulted in formation of the nitride product [Re(N)Cl(PNP)]. This first example of molecular electrochemical N2 splitting into nitride complexes enabled the use of cyclic voltammetry (CV) methods to establish the mechanism of reductive N2 activation to form the N2-bridged intermediate. CV data was acquired under Ar and N2, and with varying chloride concentration, rhenium concentration, and N2 pressure. A series of kinetic models was vetted against the CV data using digital simulations, leading to the assignment of an ECCEC mechanism (where “E” is an electrochemical step and “C” is a chemical step) for N2 activation that proceeds via initial reduction to ReII, N2 binding, chloride dissociation, and further reduction to ReI before formation of the N2-bridged, dinuclear intermediate by comproportionation with the ReIII precursor. Experimental kinetic data for all individual steps could be obtained. The mechanism is supported by density functional theory computations, which provide further insight into the electronic structure requirements for N2 splitting in the tetragonal frameworks enforced by rigid pincer ligands.

中文翻译:


铼钳络合物化学和电化学 N2 裂解机理



提出了二氯化铼配合物 [ReCl2(PNP)] 还原时 N2 活化和分裂成末端氮化物配体的综合机制研究 (PNP– = N(CH2CH2PtBu2)2–)。使用化学还原剂的低温研究能够全面表征 N2 桥连中间体 [{(PNP)ClRe}2(N2)] 和 N-N 键断裂过程的动力学分析。室温下的受控电位电解也导致氮化物产物[Re(N)Cl(PNP)]的形成。这是分子电化学 N2 分裂成氮化物络合物的第一个例子,使得能够使用循环伏安法 (CV) 方法来建立还原 N2 活化形成 N2 桥中间体的机制。 CV 数据是在 Ar 和 N2 下以及不同的氯化物浓度、铼浓度和 N2 压力下获得的。使用数字模拟根据 CV 数据对一系列动力学模型进行了审查,从而为 N2 活化分配了 ECCEC 机制(其中“E”是电化学步骤,“C”是化学步骤),该机制通过初始还原进行至ReII、N2 结合、氯离子解离,并在通过与 ReIII 前体发生比例化形成 N2 桥接双核中间体之前进一步还原为 ReI。可以获得所有单独步骤的实验动力学数据。该机制得到了密度泛函理论计算的支持,该计算进一步深入了解了由刚性钳形配体强制执行的四方框架中 N2 分裂的电子结构要求。
更新日期:2018-06-01
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