Formation of dinuclear iridium complexes by NHC-supported C–H bond activation

Abstract

The formation of dinuclear iridium complexes by NHC-supported aryl-CH bond activation reactions is reported. Complex IrH5(PiPr3)2 (1) reacts with 1,3-bis(3-methylimidazolium)benzene bis(tetrafluoroborate) ([C6H4(HImMe)2][BF4]2) to give the dinuclear species {[IrH2(PiPr3)2]2[μ-C6H2(ImMe)2]} (2), with a core formed by five fused rings. Complex 1 also reacts with 1,1′-diphenyl-3,3′-alkylenediimidazolium dihalides ([(CH2)n(HImC6H5)2]X2; n = 2, 3, 4). The reactions lead to the dinuclear complexes {[IrH2(PiPr3)2]2[μ-(CH2)n(ImC6H4)2]} (n = 2 (3), 3 (4), 4 (5). These compounds can be described as two six-coordinate d6-iridium dihydride metal fragments containing an orthometalated phenylimidazolylidene, which are connected through an alkylene linker. In contrast to the diimidazolium salts, 1,1′-diphenyl-3,3′-methylenedibenzimidazolium dibromide ([CH2(HBzImC6H5)2]Br2) reacts with 1 to give a 1:1 mixture of the mononuclear complexes IrH2Br{κ-N-(HBzImC6H5)}(PiPr3)2 (6) and IrH2{κ2-C,C-(MeBzImC6H4)}(PiPr3)2 (7). The latter and its analogous IrH2{κ2-C,C-(PhBzImC6H4)}(PiPr3)2 (8) can be also obtained, as pure solids, by means of the reactions of 1 with 1-methyl-3-phenylbenzimidazolium tetrafluoroborate and 1,3-diphenylbenzimidazolium chloride, respectively.