Mechanistic Insight into Water Oxidation Catalysis by a Mononuclear Ruthenium Complex

IF 4.3 2区化学 Q1 CHEMISTRY, INORGANIC & NUCLEAR

Inorganic Chemistry Pub Date : 2025-04-18 DOI:10.1021/acs.inorgchem.5c00138

Takahiko Kojima, Tomoki Takaoka, Yusuke Chiba, Hiroaki Kotani, Hiroto Fujisaki, Tomoya Ishizuka, Sachiko Yanagisawa, Minoru Kubo, Yoshihito Shiota, Kazunari Yoshizawa

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Abstract

A reaction mechanism of water oxidation involving a mononuclear Ru^IV-oxo complex (1) as an intermediate with use of (NH₄)₂[Ce^IV(NO₃)₆] (CAN) as an oxidant has been scrutinized to provide a clear view of O–O bond formation and O₂ release. This work includes the spectroscopic and theoretical characterization of an end-on Ru^III-superoxo complex (3), together with the crystallographic characterization of a side-on Ru^IV-peroxo complex (4) which should be in equilibrium with 3 in an aqueous solution. The formation of the Ru^V-oxo intermediate as a responsible species for the water oxidation was supported by a square wave voltammogram of 1 in an aqueous solution, showing an oxidation wave at +1.52 V (vs NHE) which is accessible with use of excess CAN through an electron-transfer equilibrium. Kinetic analysis and isotope labeling experiments supported a water nucleophilic attack (WNA) mechanism in the water oxidation. The stability of 3 as a product of WNA allowed us to detect it in aqueous solution. The diamagnetic character of 3 enabled the detailed kinetic investigation of O₂-releasing from the intermediate to determine activation parameters. Herein, a new insight was gained into the O₂ release from 3 as the final step of water oxidation by the mononuclear Ru catalyst.

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单核钌配合物催化水氧化的机理研究

研究了以（NH4）2[CeIV(NO3)6] （CAN）为氧化剂的单核RuIV-oxo络合物(1)为中间体的水氧化反应机理，为O-O键形成和O2释放提供了清晰的视角。这项工作包括端对ruiii -超氧配合物(3)的光谱和理论表征，以及在水溶液中与3平衡的侧对ruiv -过氧配合物(4)的晶体学表征。RuV-oxo中间体作为水氧化的负责物质的形成得到了水溶液中方波伏安图1的支持，显示出在+1.52 V （vs NHE）下的氧化波，通过电子转移平衡可以使用过量的CAN。动力学分析和同位素标记实验支持水氧化的亲核攻击（WNA）机制。3作为WNA产物的稳定性使我们能够在水溶液中检测到它。由于3的抗磁性，可以对中间体释放o2的动力学进行详细研究，从而确定活化参数。本文对单核Ru催化剂氧化水的最后一步——3的O2释放有了新的认识。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Inorganic Chemistry 化学-无机化学与核化学

CiteScore

7.60

自引率

13.00%

发文量

1960

审稿时长

1.9 months

期刊介绍： Inorganic Chemistry publishes fundamental studies in all phases of inorganic chemistry. Coverage includes experimental and theoretical reports on quantitative studies of structure and thermodynamics, kinetics, mechanisms of inorganic reactions, bioinorganic chemistry, and relevant aspects of organometallic chemistry, solid-state phenomena, and chemical bonding theory. Emphasis is placed on the synthesis, structure, thermodynamics, reactivity, spectroscopy, and bonding properties of significant new and known compounds.