Redetermination of di-μ-hydrido-hexahydridotetrakis(tetrahydrofuran)dialuminium(III)magnesium(II) (original) (raw)
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Magnesium Borohydride: Synthesis and Crystal Structure
Angewandte Chemie International Edition, 2007
Owing to their light weight, complex p-metal hydrides are of interest for hydrogen storage in mobile applications. Magnesium borohydride (Mg(BH 4 ) 2 ), which has been known since the 1950s, has a theoretical hydrogen capacity of 14.8 wt %. Although this compound is thermally quite stable (decomposition temperature of ca. 300 8C) and, thus, less suitable for reversible storage applications, it is of interest as a complex pmetal hydride. There have been several reports on the preparation and structure of solvates of Mg(BH 4 ) 2 , but few on the solvent-free compound. Early work suggested the existence of two crystalline modifications of Mg(BH 4 ) 2 , a tetragonal low-temperature (LT) phase and a cubic hightemperature (HT) phase. The density of the LT phase was given as 0.989 g cm À3 and the phase-transition temperature as 186 8C. No structural data were reported, owing to difficulties in obtaining crystalline products of sufficient quality for diffraction methods.
Facile High-Yield Synthesis of Pure, Crystalline Mg(BH 4 ) 2
Inorganic Chemistry, 2007
Magnesium borohydride, Mg(BH 4 ) 2 , a long-sought candidate for efficient hydrogen storage chemisorption technology, has been obtained in a pure and crystalline form by two new synthetic routes in a hydrocarbon solvent. A first synthetic approach involves a metathetical reaction between organometallic magnesium compounds; a second route consists of an insertion reaction of BH 3 species, released from BH 3 ‚S(CH 3 ) 2 , into the Mg−C bonds of MgR 2 , with complete replacement of R groups with BH 4 groups. Both methods, based on commercially available reagents, afford identical, pure, polycrystalline materials, identified by X-ray diffraction as the so-called low-temperature hexagonal form of Mg(BH 4 ) 2 , stable below 180°C, recently shown to possess a complex, unpredictable, crystal structure.
ChemInform Abstract: Structural and Spectroscopic Study of Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6
ChemInform, 2009
Key words magnesium hydrogen vanadate(V), hydrothermal synthesis, crystal structure, infrared spectra, hydrogen vanadate(V). PACS 61.66. Fn, 81.05.Rm, 61.05.cp, 78.30.Hv Single-crystals of the polar compound magnesium hydrogen vanadate(V), Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6 , were synthesized hydrothermally. It represents the first hydrogen vanadate(V) among inorganic compounds. Its structure was determined by single-crystal X-ray diffraction [space group P6 3 mc, a = 12.9096(2), c = 5.0755(1) Å, V = 732.55(2) ų, Z = 1]. The crystal structure of Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6 consists of well separated, vacancy-interrupted chains of face sharing Mg2O 6 octahedra, with short Mg2-Mg2 distances of 2.537(1) Å, embedded in a porous magnesium vanadate 3D framework having the topology of the zeolite cancrinite. All three hydrogen positions in the structure were confirmed by FTIR spectroscopy.
Inorganic Chemistry, 1989
Rh2(MeN(P(OMe)2)2)4(pMe02CC=CC02Me)] (C104)2.MeOHu Rh2-Rhl-P1 86.58 (3) P6-Rh2-P7 96.79 (5) Rh2-Rhl-P2 92.39 (3) P6-Rh2-P8 88.90 (5) Rh2-Rhl-P3 169.49 (4) P6-Rh2-C6 159.3 (1) RhZ-Rhl-P4 108.09 (3) P7-Rh2-P8 68.58 (5) Rh2-Rhl-C5 70.30 (8) P7-Rh2-C6 103.7 (1) PI-Rh 1-P2 94.80 (5) P8-Rh2-C6 96.3 (1) P1 -Rh 1 -P3 96.54 (5) Rhl-PI-N1 117.9 (2) PI-Rhl-P4 163.71 (5) Rhl-P2-N2 115.8 (2) P 1 -Rh 1 -C5 91.1 (1) Rhl-P3-N3 96.8 (2) P2-Rh 1-P3 97.33 (5) Rhl-P4-N3 93.4 (2) P2-Rh 1-P4 91.70 (5) Rh2-P5-N1 114.9 (2) P2-Rhl-C5 161.4 (1) Rh2-P6-N2 116.4 (2) P3-Rhl-P4 67.78 (5) Rh2-P7-N4 94.5 (2) P3-Rhl-C5 99.6 (1) Rh2-P8-N4 95.2 (2) P4-Rh 1-C5 87.4 (1) PI-Nl-P5 115.6 (2)
Magnesium compounds: Classification and analysis of crystallographic and structural data
Journal of Organometallic Chemistry, 1994
215(-, 2) Br 325(-, 7) Mg(Me,Si)z(dme) (pale pink) or 1646.1(2) 934.8(l) 1195.0(2) m 1214.7(2) P2,/c 1266.1(4) 4 1201.6(5) or 1190.2(4) Cmca 1120.1(3) 8 1836.7(6) 0 212.4(4, 0) Si 263.0(2,0) MgtMe)z(C,Hr& (not given) N 223.X6,8) C 219.4(9,31) 108.94(18) MdMe)z(Me4en) (wlourless) N 224.2(6, 15) CfMe) 216.6(6,0) 96.1(2) MgW,
Structural and spectroscopic study of Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6
Crystal Research and Technology, 2008
Key words magnesium hydrogen vanadate(V), hydrothermal synthesis, crystal structure, infrared spectra, hydrogen vanadate(V). PACS 61.66. Fn, 81.05.Rm, 61.05.cp, 78.30.Hv Single-crystals of the polar compound magnesium hydrogen vanadate(V), Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6 , were synthesized hydrothermally. It represents the first hydrogen vanadate(V) among inorganic compounds. Its structure was determined by single-crystal X-ray diffraction [space group P6 3 mc, a = 12.9096(2), c = 5.0755(1) Å, V = 732.55(2) ų, Z = 1]. The crystal structure of Mg 13.4 (OH) 6 (HVO 4 ) 2 (H 0.2 VO 4 ) 6 consists of well separated, vacancy-interrupted chains of face sharing Mg2O 6 octahedra, with short Mg2-Mg2 distances of 2.537(1) Å, embedded in a porous magnesium vanadate 3D framework having the topology of the zeolite cancrinite. All three hydrogen positions in the structure were confirmed by FTIR spectroscopy.
Ab initio study of Mg (Al H4 )2
Physical Review B, 2005
Magnesium alanate Mg(AlH4)2 has recently raised interest as a potential material for hydrogen storage. We apply ab initio calculations to characterize structural, electronic and energetic properties of Mg(AlH4)2 . Density functional theory calculations within the generalized gradient approximation (GGA) are used to optimize the geometry and obtain the electronic structure. The latter is also studied by quasi-particle calculations at the GW level. Mg(AlH4)2 is a large band gap insulator with a fundamental band gap of 6.5eV . The hydrogen atoms are bonded in AlH4 complexes, whose states dominate both the valence and the conduction bands. On the basis of total energies, the reaction enthalpy for decomposing Mg(AlH4)2 into bulk magnesium, bulk aluminum and hydrogen gas is 0.17eV/H2 (at T=0 ). Including corrections due to the zero point vibrations of the hydrogen atoms this number decreases to 0.10eV/H2 . The enthalpy of the dehydrogenation reaction Mg(AlH4)2→MgH2+2Al+3H2(g) is close to zero, which impairs the potential usefulness of magnesium alanate as a hydrogen storage material.
Structure of a new ternary compound with high magnesium content, so-called Gd13Ni9Mg78
Acta Materialia, 2012
The magnesium metal rich composition Gd 13 Ni 9 Mg 78 was synthesized from the elements in sealed tantalum tubes in an induction furnace. According to the X-ray diffraction, the EPMA analyses and the dark field images obtained by TEM, a new compound with a composition ranging from Gd 10-15 Ni 8-12 Mg 72-78 and low crystallinity was brought to light. In order to increase the crystallinity, different experimental conditions were investigated for numerous compounds with the initial composition Gd 13 Ni 9 Mg 78. Also, several heat treatments (from 573 K to 823 K) and cooling rates (from room temperature quenched down to 2 K/h) have been tested. The best crystallinity was obtained for the slower cooling rates ranging from 2 to 6 K/h. From the more crystallized compounds, the structure was partially deduced using the transmission electron microscopy and an average cubic structure with lattice parameter a = 4.55 Å could be assumed. A modulation along both a*and b* axis with vectors of modulation q1 = 0.42a* and q2 = 0.42b* was observed. This compound so-called Gd 13 Ni 9 Mg 78 absorbs around 3 wt% of hydrogen at 603 K, 30 bars and some fair reversibility is possible, because after the first hydrogenation, irreversible decomposition into MgH 2 , GdH 2 and NiMgH 4 has been shown. The pathway of the reaction is described herein. The powder mixture after decomposition shows an interesting kinetics for magnesium without ball milling.