Reactions of phosphine ligands with iridium complexes leading to C(sp3)-H bond activation

Treatment of [Ir-2(mu-Cl)(2)(coe)(4)] (coe = cyclooctene) with the short-bite bifunctional N,P-donor ligand 1-benzyl-2-imidazolyldiphenylphosphine (Ph(2)PBnIm) resulted in the oxidative addition of the C(Sp(3))-H bond from the benzyl group to the metal to give [IrHCl{Ph2P(CHPh)Im}(Ph(2)PBnIm)] (1), fully characterized by an X-ray study. The related ligand 2-pyridyldiphenylphosphine (Ph2PPy) reacted with [Ir-2(mu-Cl)(2)(coe)(4)] to give the mononuclear iridium(I) complex [IrCl(Ph2PPY)(2)] (2), which showed P,N-chelating and P-coordinated ligands. Addition of Ph(2)PBnIm to 2 produced the replacement of the P-coordinated Ph2PPY ligand along with the benzyl C-H bond addition to iridium to give [IrHCl{Ph2P(CHPh)Im}-(Ph2PPy)]. This result indicates that mononuclear complexes of the type [IrCl(Ph(2)PBnIm)(L)] (L = P,N-chelating ligand) are the active species undergoing the C-H bond activation reaction. A related C-H bond activation process of the methylene group of dppm occurs in the reaction of [Ir-2(mu-Cl)(2)(coe)(4)] with dppm in toluene to give the hydrido complex with one deprotonated dppm ligand [IrHCl(Ph2PCHPPh2)(dppm)] (4). On the other hand, the hydride migrates to the methanide carbon in 4 on dissolving the complex in CD2Cl2 to establish an equilibrium with [IrCl(dppm)(2)] without H/D exchange. Protonating agents such as HBF4 center dot Et2O and water reacted with complex 4 easily to give [IrHCl(dppm)(2)]X (X = BF4, OH). The mononuclear complex 2 was found to be highly reactive. Reactions of 2 with O-2, H-2, and dichloromethane gave the complexes [IrCl(O-2)(Ph2PPy)(2)], [IrCl(H)(2)(Ph2PPy)(2)], and [IrCl2(CH2Cl)(Ph2PPy)(2)], respectively.