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Some metal hydrides form when a metal complex is treated with hydrogen in the presence of a base. The reaction involves no changes in the oxidation state of the metal and can be viewed as splitting H 2 into hydride (which binds to the metal) and proton (which binds to the base). ML n x+ + base + H 2 ⇌ HML n (x-1)+ + Hbase +
The first applications of metal hydrides were made by NASA to demonstrate long-term hydrogen storage for use in space propulsion. In the 1970s, automobiles, vans, and forklifts were demonstrated. [6] The metal hydrides were used for hydrogen storage, separation, and refrigeration.
Classical transition metal hydride feature a single bond between the hydrogen centre and the transition metal. Some transition metal hydrides are acidic, e.g., HCo(CO) 4 and H 2 Fe(CO) 4. The anions potassium nonahydridorhenate [ReH 9] 2− and [FeH 6] 4− are examples from the growing collection of known molecular homoleptic metal hydrides. [16]
Proposed hydrides for use in a hydrogen economy include simple hydrides of magnesium [19] or transition metals and complex metal hydrides, typically containing sodium, lithium, or calcium and aluminium or boron. Hydrides chosen for storage applications provide low reactivity (high safety) and high hydrogen storage densities.
In general, complex metal hydrides have the formula M x M' y H n, where M is an alkali metal cation or cation complex and M' is a metal or metalloid.Well known examples feature group 13 elements, especially boron and aluminium including sodium aluminium hydride, NaAlH 4), lithium aluminium hydride, LiAlH 4, and lithium borohydride, (LiBH 4).
Hydrogen enhanced decohesion (HEDE): Interstitial hydrogen lowers the stress required for metal atoms to fracture apart. HEDE can only occur when the local concentration of hydrogen is high, such as due to the increased hydrogen solubility in the tensile stress field at a crack tip, at stress concentrators, or in the tension field of edge ...
Transition metal hydride complexes can be used in place of organosilanes as the hydride source. In these cases, triflic acid is a typical proton donor. Ketones such as benzophenones, and 1,1-disubstituted olefins are typical substrates. Hydrides of tungsten, chromium, osmium, and molybdenum complexes have also been reported.
This was tried in operation Upshot–Knothole, [7] where hydrogen was used to reduce the critical mass. The test explosions codenamed Ruth and Ray used in the core uranium hydride. Ruth used the hydrogen isotope protium (1 H) and Ray used the hydrogen isotope deuterium (2 H or 2 D) as neutron moderators. The predicted yield was 1.5 to 3 kt TNT ...