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Mg6Ir2H11, a new metal hydride containing saddle-like [IrH4] and square-pyramidal [IrH5] hydrido complexes |
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| Authors: | R erný J -M Joubert H Kohlmann K Yvon |
| Affiliation: | a Laboratoire de Cristallographie, Université de Genève, 24 Quai E. Ansermet, 1211 Genève 4, Switzerland b Laboratoire de Chimie Métallurgique des Terres Rares, CNRS, 2–8 rue Henri Dunant, 94320 Thiais Cedex, France c High Pressure Science and Engineering Center, University of Nevada, 4505 South Maryland Parkway, Las Vegas, NV 89154-4002, USA |
| Abstract: | Mg6Ir2H11 has been synthesised by both hydrogenation of the intermetallic compound Mg3Ir at 20 bar and  300 °C, and sintering of the elements at 500 °C under 50 bar hydrogen pressure. Neutron powder diffraction on the deuteride indicates a monoclinic structure (space group P21/c, Mg6Ir2D11: a=10.226(1), b=19.234(2), c=8.3345(9) Å, β=91.00(1)°, T=20 °C) that is closely related to orthorhombic Mg6Co2H11. It contains a square-pyramidal IrH5]4? complex and three saddle-like IrH4]5? complexes of which one is ordered and two are disordered. Five hydride anions H? are exclusively bonded to magnesium. The compound has a red colour, is presumably non-metallic and decomposes under 3 bar argon at 500 °C into Mg3Ir, iridium and a previously unreported intermetallic compound of composition Mg5Ir2. |
| Keywords: | Hydrogen absorbing materials Gas–solid reactions Crystal structure X-ray diffraction Neutron diffraction |
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