A procedure was developed for the synthesis of trinuclear cyclic (ZrIII)2—Al hydrides [(Cp2Zr)2(μ-H)](μ-H)2AlX2 (X = Cl (1a) or Br (1b)). These complexes were prepared in 60–65% yields by the reaction of Cp2ZrX2 with LiAlH4 in the presence of CoBr2 and tolane. The structures of complexes 1a and 1b and iodide 1c (X = I) were studied by NMR spectroscopy in solvents of different basicities (toluene, THF, and pyridine). Complex 1a is unsolvated and monomeric in all solvents; complex 1b, in toluene and THF; complex 1c, in toluene only. At room temperature, complex 1a does not catalyze hydrogenation of hex-1-ene and does not react with tolane, but reacts with the latter at high temperature
to give bis(η5-cyclopentadienyl)-2,3,4,5-tetraphenylzirconacyclopentadiene. The reaction of equivalent amounts of complex 1a and HCl produces the [(Cp2Zr)2(μ-Cl)](μ-H)2AlCl2 complex. The structure of the latter was established by X-ray diffraction.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2418–2423, November, 2005. 相似文献
A series of novel arylgermanium hydrides ArnGeH4–n (n = 1–3) and diaryl(chloro)germanium hydrides Ar2Ge(Cl)H were synthesized and characterized. Systematic preparation and purification were achieved via the lithium chloride–triflic acid and the optimized Grignard route. Arylgermanium hydrides ArnGeH4–n (Ar = 2,5-Me2C6H3, n = 1–3) were characterized by 1H and 73Ge NMR spectroscopy and single crystal X-ray diffractometry. 相似文献
Reaction of [W(PMe2Ph)3H6] with pentaborane(9) gives nido-2-[W(PMe2Ph)3H2B4H8] (1) as well as nido-2-[W(PMe2Ph)3HB5H10] (2). The crystal structure of (2) has been determined. Compound (2) has a novel metallaborane structure containing an edge-bridging {BH3} group between the tungsten atom and one of the basal boron atoms in a “nido-WB4” pyramid. Reaction of [W(PMe3)4(η2-CH2PMe2)H] with pentaborane(9) gives nido-2-[W(PMe3)3H2B4H8] (3) whilst reaction of [Mo(L)4H4] with pentaborane(9) gives nido-2-[Mo(L)3H2B4H8] [L = PMe3 (4), PMe2Ph (5)]. Treatment of [Mo(PMe3)4H4] with excess BH3 · thf gives the known borohydride [Mo(PMe3)4H(η2-BH4)]. 相似文献
Bonding, structure, and stability of solid A2MH2 with A = Li, Na; M = Pd, Pt were investigated with a relativistically corrected density-functional approach, which reliably describes the trends among these four compounds. In order to examine the influence of the ligands (A) and of the crystalline environment, calculations were also made for free A2MH2 molecules and MH22– ions. The free MH22– complex is held together by strong bonds between formally closed shell atomic units because of strong M-d,s hybridization. The M–H bonds are further stabilized by the alkali metal ion ligands and by the crystal surrounding. The crystal field expands the H–A distance and enhances the H–A polarity. Relativistic effects contribute to M–H bonding in the solid state. The experimentally determined bond lengths and their trends are in accordance with theory. Due to relativistic and lanthanide effects, the Pt–H bond length becomes nearly as short as the Pd–H one. The small Li ion causes a distortion of the Li2PtH2 crystal resulting in an even shorter Pt–H bond length. In the gas-phase, A2PtH2 is more stable against dissociation than A2PdH2. The stability of the solid compounds is strongly influenced by the cohesive energy of the metal M, and also by the nature of the alkali metal. The evaluated enthalpies of formation favor increasing stability of solid A2MH2 against disproportionation into M and AH from Pt to Pd and from Li to Na. This is in agreement with experimental findings. The assignment of the experimental vibrational excitations should be reconsidered. 相似文献
Solid‐state hydrogen storage using various materials is expected to provide the ultimate solution for safe and efficient on‐board storage. Complex hydrides have attracted increasing attention over the past two decades due to their high gravimetric and volumetric hydrogen densities. In this account, we review studies from our lab on tailoring the thermodynamics and kinetics for hydrogen storage in complex hydrides, including metal alanates, borohydrides and amides. By changing the material composition and structure, developing feasible preparation methods, doping high‐performance catalysts, optimizing multifunctional additives, creating nanostructures and understanding the interaction mechanisms with hydrogen, the operating temperatures for hydrogen storage in metal amides, alanates and borohydrides are remarkably reduced. This temperature reduction is associated with enhanced reaction kinetics and improved reversibility. The examples discussed in this review are expected to provide new inspiration for the development of complex hydrides with high hydrogen capacity and appropriate thermodynamics and kinetics for hydrogen storage.
A procedure for the direct synthesis of dialkoxyaluminum hydrides (RO)2AlH (R=Pri, But, and Et) from aluminum metal and corresponding alcohols in organic solvents (hydrocarbons, ethers) in the presence of catalytic
amounts of tertiary amines (NMe3, NEt3) at a pressure of H2 of 80 to 350 atm and at a temperature of 100 to 160°C has been developed. A possible mechanism for the reaction was proposed.
Thermal decomposition of (RO)2AlH was studied by differential thermogravimetric analysis (DTGA),27Al NMR spectroscopy, IR spectroscopy, and GLC.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2052–2055, November, 1997. 相似文献