Mild Oxidative Addition of C–H Bonds to a Hydrido-Bridged Dinuclear Complex of Iridium(II) Induced by the Coordination of Heteroatomic Ligands



The oxidative addition of C–H bonds to a dinuclear complex of divalent iridium, [Cp*Ir(μ-H)]2 (1), has been investigated. Reactions of 1 with phosphorus compounds containing a phenyl ring (PR1R2Ph) at ambient temperature gave novel five-membered diiridacyclic [(Cp*IrH)2(μ-H)(μ-R1R2PC6H4)] [R1 = R2 = Me (2a); R1 = Me, R2 = Ph (2b); R1 = R2 = Ph (2c); R1 = R2 = OEt (2d); and R1 = OEt, R2 = Ph (2e)] complexes through ortho-C–H activation of the phenyl ring bound to the phosphorus atom. The reaction of 1 with tripropylphosphane gave a new four-membered diiridacyclic [(Cp*IrH)2(μ-H)(μ-Pr2PCHCH2CH3)] (3) complex in a similar manner. On the other hand, the reaction of 1 with triethyl phosphite gave a Cp*-metalated product, [Ir(H)(P(OEt)3)(μ,η51-C5Me4CH2)(μ-H)Ir(H)(Cp*)] (4), through C–H activation of a methyl group on one of the Cp* ligands. Furthermore, similar mild C–H activation reactions of 1 with sulfoxides have also been revealed. Thus, reactions of 1 with dimethyl sulfoxide and a couple of sulfoxides containing phenyl groups brought about the activation of the C–H bonds of a methyl group and a phenyl group to give [(Cp*IrH)2(μ-H)(μ-MeS(=O)CH2)] (5) and [(Cp*IrH)2(μ-H)(μ-RS(=O)C6H4)] [R = Me (6a) and R = Ph (6b)], respectively. The structures of 2a, 4, 5, and 6a have been confirmed by X-ray analysis. A plausible reaction pathway for these C–H activation reactions has been proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)