Reinvestigation of Water Oxidation Catalyzed by a Dinuclear Cobalt Polypyridine Complex: Identification of CoOx as a Real Heterogeneous Catalyst

Recently, a dinuclear cobalt complex, [(TPA)Co III (μ-OH)(μ-O 2 )Co III (TPA)](ClO 4 ) 3 ( 1; TPA = tris(2-pyridylmethyl)amine), has been reported as a homogeneous catalyst for electrochemical and photochemical water oxidation ( Angew. Chem. Int. Ed. 2014, 53, 14499). During the reinvestigation of the reported water oxidation catalyst (WOC) of 1, several characterizations such as EDTA and bipyridine titrations, electrochemistry, SEM, EDX, ICP-AES, TEM, XPS, and UV–vis spectroscopy have revealed that the water oxidation may happen due to the formation of CoO x as a real heterogeneous WOC, and 1 itself lacks the ability to catalyze water oxidation. This paper presents a practical and simple procedure to clarify whether the water oxidation is truly catalyzed by a molecular catalyst or not.