HETEROPOLYMETALLIC COMPLEXES OF 1,1'-BIS(DIPHENYLPHOSPHINO)FERROCENE (DPPF) .5. SYNTHESIS AND CHARACTERIZATION OF THE CATIONIC COMPLEXES [RH(DPPF)2]+, [IR(DPPF)2]+ - CRYSTAL AND MOLECULAR-STRUCTURE OF [IR(DPPF)2]B(C6H5)4

Ferrocenylbis(phosphine) complexes of the type [M(dppf)2]X (M = Rh (1), Ir (2, 4); dppf = 1,1′-bis(diphenylphosphino)ferrocene; X = ClO4 −, B(C6H5)4 −) have been prepared and characterized in solution by 31P NMR investigation. The two bis(phosphines) in the cationic complex [Rh(dppf)2]+ are chemically equivalent at ambient temperature, but they exhibit AA′BB′X and A2M2X patterns in their 31P NMR spectrum at −90 °C. These patterns are indicative of a dimeric complex, [Rh(dppf)(μ-dppf)h2+ (5), as predominant species in solution, in equilibrium with the pentacoordinated fluxional trigonal-bipyramidal species [Rh(dppf)2S]+ (6), in which a solvent molecule occupies an equatorial position. A similar temperature dependence of the 31P NMR spectrum is exhibited by [Ir(dppf)2]B(C6H5)4. This has been further characterized by single-crystal X-ray diffraction analysis. The complex crystallizes in the monoclinic system, space group C2/c, with a = 41.814 (5) Å, b = 14.886 (5) Å, c = 26.515 (5) Å, β = 94.62 (3) °, and Z = 8. In the cation [Ir(dppf)2]+, the four P atoms are directly bonded to the metal atom with Ir-P distances ranging from 2.32 to 2.39 Å. The coordination geometry around the metal center is intermediate between square planar and tetrahedral, and it reveals the largest tetrahedral distortion for a d8 complex reported so far. Under certain conditions, the neutral cyclometalated Ir(III) complex [Ir(dppf)(H)(Cl)]2(μ-dppf(-2H)) (3) was isolated and spectroscopically characterized. © 1990, American Chemical Society. All rights reserved.