New cationic rhodium(I)-iridium(III) complexes with bridging hydride and chloride ligands. Synthesis and x-ray crystal structure of [(diphos)Rh(.mu.-H)(.mu.-Cl)IrCl(PEt3)3]BF4 and [(diphos)Rh(.mu.-H)(.mu.-Cl)IrH(PEt3)3]BF4

Reaction of [(diphos)Rh(acetone)2]BF4 with mer,trans-IrHCl2L3 (L = PMe2Ph, PEt2Ph, PEt3; diphos = Ph2PCH2CH2PPh2) affords the hydrido-bridged dinuclear complexes [(diphos)Rh(μ-H)(μ-Cl)IrClL3]BF4. Solution studies show that the bridging ligands are only weakly coordinated to the rhodium. The molecular structure of 3 (L = PEt3) has been determined by X-ray diffraction: monoclinic, space group P21/c, Z = 4, a = 11.786 (2) Å, b = 19.673 (4) Å, c = 22.571 (4) Å, β = 89.88 (1)°. The structure was solved by Patterson and Fourier methods using 5750 observed reflections [I ≥ 3σ(I)] and refined to a conventional R = 0.057. The coordination around rhodium is distorted square planar and that around iridium is distorted octahedral. The Rh-Ir distance is 2.903 (1) Å, and the bridging chlorine atom is almost symmetrically bonded to the metals (Rh-Cl = 2.386 (3), Ir-Cl = 2.381 (3) Å). The isoelectronic complex [(diphos)Rh(μ-H)(μ-Cl)IrH(PEt3)3]BF4 was obtained in a similar reaction, starting from mer,cis-IrH2Cl(PEt3)3. Its structure determined by X-ray diffraction, as above, is monoclinic, space group P21, Z = 2, a = 11.102 (2) Å, b = 13.582 (3) Å, c = 16.694 (4) Å, β = 85.06 (2)°. The final agreement factor (for the 4553 observed reflections) R is 0.062. As for compound 3 the coordination around Rh and Ir is distorted square planar and octahedral, respectively. There is a pronounced asymmetry in the chlorine bridge (Rh-Cl = 2.394 (5), Ir-Cl = 2.510 (5) Å), and the metal-metal separation is 2.969 (2) Å.