Nichols Asa W, Chatterjee Sayanti, Sabat Michal, Machan Charles W
Department of Chemistry, University of Virginia , McCormick Road, PO Box 400319, Charlottesville, Virginia 22904-4319, United States.
Inorg Chem. 2018 Feb 19;57(4):2111-2121. doi: 10.1021/acs.inorgchem.7b02955. Epub 2018 Jan 31.
The synthesis, structural characterization, and reactivity of an iron(III) chloride compound of 6,6'-di(3,5-di-tert-butyl-2-hydroxybenzene)-2,2'-bipyridine (Fe(dhbpy)Cl), under electrochemically reducing conditions is reported. In the presence of carbon dioxide (CO) under anhydrous conditions in N,N-dimethylformamide (DMF), this complex mediates the 2e reductive disproportionation of two equivalents of CO to carbon monoxide (CO) and carbonate (CO). Upon addition of phenol (PhOH) as a proton source under CO saturation, catalytic current is observed; product analysis from controlled potential electrolysis experiments shows the majority product is formate (68 ± 4% Faradaic efficiency), with H as a minor product (30 ± 10% Faradaic efficiency) and minimal CO (1.1 ± 0.3% Faradaic efficiency). On the basis of data obtained from cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC), the release of CO from intermediate Fe carbonyl species is extremely slow and undergoes competitive degradation, limiting the activity and lifetime of this catalyst. Mechanistic studies also indicate the phenolate moieties coordinated to Fe are sensitive to protonation in the reduced state, suggesting the possibility of cooperative pendent proton interactions being involved in CO reduction.
报道了6,6'-二(3,5-二叔丁基-2-羟基苯)-2,2'-联吡啶的氯化铁(III)化合物(Fe(dhbpy)Cl)在电化学还原条件下的合成、结构表征及反应活性。在无水N,N-二甲基甲酰胺(DMF)中，在二氧化碳(CO₂)存在下，该配合物介导两当量的CO₂发生2e还原歧化反应生成一氧化碳(CO)和碳酸盐(CO₃²⁻)。在CO₂饱和条件下加入苯酚(PhOH)作为质子源时，观察到催化电流；控制电位电解实验的产物分析表明，主要产物是甲酸盐(法拉第效率为68±4%)，氢气是次要产物(法拉第效率为30±10%)，一氧化碳最少(法拉第效率为1.1±0.3%)。根据循环伏安法和红外光谱电化学(IR-SEC)获得的数据，中间体铁羰基物种释放CO的速度极慢且会发生竞争性降解，限制了该催化剂的活性和寿命。机理研究还表明，与铁配位的酚盐部分在还原态下对质子化敏感，这表明协同的悬垂质子相互作用可能参与了CO₂还原反应。
