Leuchtkaefer

Novel iridium(III) di-NHC complexes have been synthesized by transmetalation of the dicarbene ligand from the corresponding dicarbene silver complex. The iridium(III) complex [IrClCp*(di-NHC)](PF₆) (2; di-NHC = 1,1′-dimethyl-3,3′-ethylenediimidazole-2,2′-diylidene) behaves as an efficient catalyst for the oxidation of water by using Ce^IV or NaIO₄ as sacrificial oxidants, reaching a TOF of 0.20 s^–1, comparable with the most active catalysts reported in the literature. Complex 2 also displays remarkable catalytic activity in the photocatalyzed oxidation of water by using [Ru(bpy)₃]²⁺ as sensitizer and persulfate as sacrificial electron acceptor. The fate of the catalyst under turnover conditions was investigated by combined spectroscopic, kinetic and GC–MS methods. In particular, EPR experiments performed under photoirradiation revealed the formation of a high-valent Ir^IV molecular intermediate involved in the primary photoinduced electron-transfer events.

The dicarbene iridium(III) complex [IrClCp*(di-NHC)](PF₆) (2) is an efficient catalyst for the oxidation of water both in the dark (Ce^IV or NaIO₄ as sacrificial oxidants) and under photoirradiation conditions {[Ru(bpy)₃]²⁺ as photosensitizer and persulfate as sacrificial electron acceptor}.