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

Treatment of [Ir(ppy)(2)(mu-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)(mu-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 B-2(pin)(2) (pin = pinacolate) afforded [Ir{4-(pin)B-ppy}(2)(dtbpy)][OTf] (7). The alkynyl complexes [Ir(4-PhC equivalent to C-ppy)(2)(dtbpy)][OTf] (8) and [Ir{4-Me-2(OH)C equivalent to C-ppy}(4-Br-ppy)(dtbpy)][OTf] (9) were prepared by cross-coupling of 2 with PhC equivalent to CSnMe3 and Me2C(OH)C equivalent to CH, respectively. Ethynylation of [Ir(fppy)(2)(dtbpy)][OTf] (fppy = 5-formyl-2-(2'-pyridyl)phenyl) with Ohira's reagent MeCOC(N-2)P(O)(OEt)(2) afforded [Ir{5-HC equivalent to C-ppy}(2)(dtbpy)][OTf] (10). The solid-state structures of 2, 5, 7, and 10 have been determined. (c) 2005 Elsevier B.V. All rights reserved.