Enhanced Proton-Coupled Electron-Transfer Reactivity by a Mononuclear Nickel(II) Hydroxide Radical Complex

作者：Daniel Ye, Tong Wu, Ankita Puri, David D. Hebert, Maxime A. Siegler, Michael P. Hendrich, Marcel Swart, Isaac Garcia‐Bosch · 发表于：Inorganic Chemistry · 年份：2024 · DOI：10.1021/acs.inorgchem.4c03370 · 被引用次数：5 · 研究领域：Metal-Catalyzed Oxygenation Mechanisms、CO2 Reduction Techniques and Catalysts、Metal complexes synthesis and properties

High Resolution Image Download MS PowerPoint Slide The synthesis, characterization, and reactivity of a NiOH core bearing a tridentate redox-active ligand capable of reaching three molecular oxidation states is presented in this paper. The reduced complex [LNiOH] 2– was characterized by single-crystal X-ray diffraction analysis, depicting a square-planar NiOH core stabilized by intramolecular H-bonding interactions. Cyclic voltammetry measurements indicated that [LNiOH] 2– can be reversibly oxidized to [LNiOH] − and [LNiOH] at very negative reduction potentials (−1.13 and −0.39 V vs ferrocene, respectively). The oxidation of [LNiOH] 2– to [LNiOH] − and [LNiOH] was accomplished using 1 and 2 equiv of ferrocenium, respectively. Spectroscopic and computational characterization suggest that [LNiOH] 2–, [LNiOH] −, and [LNiOH] are all Ni II species in which the redox-active ligand adopts different oxidation states (catecholate-like, semiquinone-like, and quinone-like, respectively). The NiOH species were found to promote H-atom abstraction from organic substrates, with [LNiOH] − acting as a 1H + /1e – oxidant and [LNiOH] as a 2H + /2e – oxidant. Thermochemical analysis indicated that [LNiOH] was capable of abstracting H atoms from stronger O–H bonds than [LNiOH] − . However, the greater thermochemical tendency of [LNiOH] reactivity toward H atoms did not align with the kinetics of the PCET reaction, where [LNiOH] − reacted with H-atom donors much faster than [LNiOH]. The unique ste...