A Non-Heme Diiron Complex for (Electro)catalytic Reduction of Dioxygen: Tuning the Selectivity through Electron Delivery

• Published in: Journal of the American Chemical Society 2019-05, Vol.141 (20), p.8244-8253
• Main Authors: Wang, Lianke, Gennari, Marcello, Cantú Reinhard, Fabián G, Gutiérrez, Javier, Morozan, Adina, Philouze, Christian, Demeshko, Serhiy, Artero, Vincent, Meyer, Franc, de Visser, Sam P, Duboc, Carole
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical Sciences
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.9b02011

In the oxygen reduction reaction (ORR) domain, the investigation of new homogeneous catalysts is a crucial step toward the full comprehension of the key structural and/or electronic factors that control catalytic efficiency and selectivity. Herein, we report a unique non-heme diiron complex that can act as a homogeneous ORR catalyst in acetonitrile solution. This iron­(II) thiolate dinuclear complex, [FeII 2(LS)­(LSH)] ([Fe 2 SH ] + ) (LS2– = 2,2′-(2,2′-bipyridine-6,6′-diyl)­bis­(1,1-diphenylethanethiolate)) contains a thiol group in the metal coordination sphere. [Fe 2 SH ] + is an efficient ORR catalyst both in the presence of a one-electron reducing agent and under electrochemically assisted conditions. However, its selectivity is dependent on the electron delivery pathway; in particular, the process is selective for H2O2 production under chemical conditions (up to ∼95%), whereas H2O is the main product during electrocatalysis (less than ∼10% H2O2). Based on computational work alongside the experimental data, a mechanistic proposal is discussed that rationalizes the selective and tunable reduction of dioxygen.