mer-Ir(pmp)3 as a strongly photoreducing and stable Ir(C^C)3 photocatalyst for metallaphotoredox catalysis

Abstract

Here we report a new homoleptic Ir(NHC) photocatalyst, mer-Ir(pmp)3 which is the first Ir(C^C)3 photocatalyst to operate effectively using excitation sources peaking in the visible (λ exc = 427, 440 and 456 nm). In line with previously reported Ir(C^C)3 photocatalysts, mer-Ir(pmp)3 is a potent photoreductant, reducing substrates up to Ered = -2.7 V vs. SCE and energy transfer catalyst, sensitizing substrates up to ET = 3.00 eV. Furthermore, mer-Ir(pmp)3 can engage in dual nickel photoredox catalysis on account of its red-shifted absorption spectrum and anodically shifted redox potentials. Compared to the literature-known photocatalysts, [Ir(dF(CF3)ppy)2(dtbbpy)]PF6, 4CzIPN and [Ru(bpy)3](PF6)2, mer-Ir(pmp)3 achieves competitive or improved yields for the amination of aryl bromides and exhibits good photostability across a range of different conditions.