Direct functionalization of the cyclometalated 2-(2′-pyridyl)phenyl ligand bound to iridium(III)

Treatment of [Ir(ppy)2(μ-Cl)]2 and [Ir(ppy)2(dtbpy)][OTf] (ppy = 2-(2′-pyridyl)phenyl; dtbpy = 4,4′-di-tert-butyl-2,2′-bipyridine; OTf = triflate) with pyridinium tribromide in the presence of Fe powder led to isolation of [Ir(4-Br-ppy)(μ-Br)]2 (1) and [Ir(4-Br-ppy)2(dtbpy)][OTf] (2), respectively. Pd-catalyzed cross-coupling of 2 with RB(OH)2 afforded [Ir(4-R-ppy)2(dtbpy)][OTf] (R = 4′-FC6H4 (3)), 4′-PhC6H4 (4), 2′-thienyl (5), 4′-C6H4CH2OH (6). Treatment of 4 with B2(pin)2 (pin = pinacolate) afforded [Ir{4-(pin)B-ppy}2(dtbpy)][OTf] (7). The alkynyl complexes [Ir(4-PhCtriple bond; length of mdashC-ppy)2(dtbpy)][OTf] (8) and [Ir{4-Me2(OH)Ctriple bond; length of mdashC-ppy}(4-Br-ppy)(dtbpy)][OTf] (9) were prepared by cross-coupling of 2 with PhCtriple bond; length of mdashCSnMe3 and Me2C(OH)Ctriple bond; length of mdashCH, respectively. Ethynylation of [Ir(fppy)2(dtbpy)][OTf] (fppy = 5-formyl-2-(2′-pyridyl)phenyl) with Ohira’s reagent MeCOC(N2)P(O)(OEt)2 afforded [Ir{5-HCtriple bond; length of mdashC-ppy}2(dtbpy)][OTf] (10). The solid-state structures of 2, 5, 7, and 10 have been determined.