Bis(diethylphosphino)methane As a Bridging Ligand in Complexes of Ir2, Rh2, and IrRh: Geminal C–H Activation of α-Olefins

Bis(diethylphosphino)methane (depm, Et2PCH2PEt2) is used as a new bridging ligand for the syntheses of a series of diiridium, dirhodium, and iridium/rhodium complexes, starting from trans-[MM′Cl2(CO)2(depm)2] (M = M′ = Ir (1); M = M′ = Rh (11); M = Ir, M′ = Rh (19)). The reduction of all three chloro compounds in aqueous KOH under an atmosphere of CO produces the neutral tricarbonyl complexes [MM′(CO)3(depm)2] (M = M′ = Ir (2); M = M′ = Rh (12); M = Ir, M′ = Rh (20)). Protonation of these tricarbonyl complexes by triflic acid (HOTf) or Brookhart’s acid (HBArF4) yields the hydride-bridged tricarbonyl complexes [MM′(CO)3(μ-H)(depm)2][X] (M = M′ = Ir (9); M = M′ = Rh (16); M = Ir, M′ = Rh (25); X = SO3CF3 or B(3,5-(CF3)2C6H3)4). Reaction of 2 with methyl triflate yields the methylene/hydride product [Ir2(H)(CO)3(μ-CH2)(depm)2][OTf] (4), while the same reaction with the dirhodium analogue (12) produces the methyl complex [Rh2(CH3)(CO)3(depm)2][OTf] (14) at below −20 °C, which upon warming to above −20 °C resu...