Bimetallic catalysts have gained attention as promising contenders, owing to the synergistic interaction between two distinct metal centers. In this study, we present two N-heterocyclic carbene iridium(III) pentamethylcyclopentadienyl complexes [Cp*Ir(fcpyNHC)Cl]PF6 (1) and [Cp*Ir(pyNHC)Cl]PF6 (2) where 1 includes a ferrocene moiety acting as a bimetallic complex. Using ceric ammonium nitrate as a sacrificial oxidant, both complexes were tested for water oxidation. Complex 2 achieved a maximum turnover number (TONmax) of 3240 and a turnover frequency (TOFmax) of 231 min-1. In comparison, complex 1 demonstrated nearly double the activity with a TONmax of 6047 and TOFmax of 431 min-1 compared to 2, which was attributed to the cooperative effect of the catalyst in water oxidation reaction. This bimetallic Fe^Ir catalyst (1) exhibited outstanding catalytic efficiency for oxygen evolution from water at ambient conditions. We identified a proposed FeIII^IrIV intermediate experimentally via UV-Vis spectroscopy and XPS study. Theoretically, this intermediate was more stable by 7.84 kcal/mol than the traditional FeII^IrV electromer intermediate. This delineates the pronounced bimetallic cooperative participation of both Fe and Ir metal centres for better activity.
Keywords: catalysis, Iron, iridium, oxygen, density functional calculations.
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