- Diphosphine-bridged binuclear polyhydride complexes of iridium and the structure of [Ir2(H)(CO)2(μ-H)2(Ph2PCH 2PPh2)2][Cl]·1.2CH2Cl 2
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The reaction of trans-[IrCl(CO)(DPM)]2 (DPM = bis(diphenylphosphino)methane) with NaBH4 under an H2 atmosphere yields the binuclear tetrahydride [Ir2(H)4(CO)2(DPM)2] (3). Addition of strong acid (HBF4·Et2O or CF3CO2H) to this complex under an H2 atmosphere causes a reversible rearrangement to the isomer [Ir2(H)2(CO)2(μ-H)2(DPM) 2] (4). If the addition of HBF4-Et2O is performed under an N2 atmosphere, the cationic trihydride [Ir2(H)(CO)2(μ-H)2(DPM)2][BF 4] (5a) is isolated instead. This compound is also formed from the reaction of 3 with Ph3C+BF4-. Protonation of 5 with HBF4·Et2O yields the dicationic tetrahydride [Ir2(H)2(CO)2(μ-H)2(DPM) 2][BF4]2 (8), and deprotonation of 5 by KOC(CH3)3 yields the dihydride [Ir2(CO)2(μ-H)2(DPM)2] (7). Compound 3 reacts with CH2Cl2 or CHCl3, yielding [Ir2(H)(CO)2(μ-H)2(DPM)2][Cl] (5b), by exchange of one hydride ligand for Cl-. Compound 5b crystallizes from CH2Cl2 with two molecules of solvent in the monoclinic space group P21/n with a = 12.794 (4) A?, b = 20.468 (5) A?, c = 20.433 (8) A?, β = 91.58 (4)°, and Z = 4. The structure refined to R = 0.080 and Rw = 0.102 on the basis of 3543 unique observed reflections and 241 parameters varied. Although the hydride ligands were not located, their positions can be inferred from the positions of the other ligands and from the spectroscopic evidence. Two hydrides bridge the Ir-Ir bond on opposite faces of the dimer and one is terminally bound. This terminal hydride causes the adjacent carbonyl to bend off the Ir-Ir axis such that the corresponding Ir-Ir-CO angle is 129 (1)°. By contrast, the other carbonyl ligand is aligned almost parallel to the Ir-Ir bond (Ir-Ir-CO angle = 163 (1)°). The metal-metal distance is 2.855 (2) A?.
- McDonald, Robert,Sutherland, Bruce R.,Cowie, Martin
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p. 3333 - 3339
(2008/10/08)
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