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Iridium(III) Complex Containing a Unique Bifurcated Hydrogen Bond Interaction Involving Ir−H···H(N)···F−B atoms. Crystal and Molecular Structure of [IrH(η1-SC5H4NH)(η2-SC5H4N)(PPh3)2](BF4)·0.5C6H6

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journal contribution
posted on 08.05.1996, 00:00 by Sunghan Park, Alan J. Lough, Robert H. Morris
A synthetic route to a new iridium(III) complex containing a novel proton hydride bonding interaction has been established. fac-IrH3(PPh3)3 reacts with 2-mercaptopyridine HSpy (Spy = 2-SC5H4N) to give the known dihydride Ir(H)22-Spy)(PPh3)2 8. Ir(H)22-Spy)(PPh3)2 reacts with HSpy.HBF4 to give [IrH(η1-SC5H4NH)(η2-SC5H4N)(PPh3)2](BF4) 9 which possesses a unique bifurcated hydrogen bonding interaction involving Ir−H···H(N)···F−B atoms with the distances of 2.0(1) Å for the H···H unit and of 2.0(1) Å for the F···H unit in the crystalline state. In solution the N−H···H−Ir interaction is maintained according to 1H T1(min) and nOe measurements. Isotope shifts in the chemical shifts of the hydride and one phosphorus of 9 have been observed in 1H and 31P{1H} NMR spectra of [IrH(η1-SC5H4ND)(η2-SC5H4N)(PPh3)2](BF4), 9-d1, prepared by the reaction of 9 with MeOD or CF3CO2D. The crystal and molecular structure of [IrH(η1-SC5H4NH)(η2-SC5H4N)(PPh3)2](BF4)·0.5C6H6 9 has been solved by X-ray analysis:  monoclinic space group P21/c with a = 17.723(3) Å, b = 10.408(1) Å, c = 26.073(4) Å, β = 108.08(1)°, V = 4572.0(11) Å3, and Z = 4. The known complex fac-IrH3(PPh3)3, 7, is made by a new and improved method by reacting mer-IrHCl2(PPh3)3 with NaOEt and H2(g). VT-1H NMR spectra (+90 to −80 °C) of the hydrides of 7 reveal that the JAA and JAX couplings change in the AA‘A‘‘XX‘X‘‘ pattern (A = 1H, X = 31P) but that the complex is not fluxional. The T1(min) value of 0.144 s for the hydrides of 7 at −60 °C (300 MHz) indicates that the shortest H-H distances are about 1.8 Å.

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