Reduced state metal hydrides

Lithium aluminium hydride if carelessly manipulated may be dangerous for two distinct reasons. The material is caustic, and should not be allowed to touch the skin it is particularly important that the finely divided material should be kept away from the lips, nostrils and eyes, and consequently pulverisation in a mortar must be carried out with the mortar in a fume-cupboard, and with the window drawn down as far as possible in front of the operator. This danger from handling has however been greatly reduced, for the hydride is now sold in stated amounts as a coarse powder enclosed in a polythene bag in a metal container this powder dissolves readily in ether, and preliminary pulverisation is unnecessary. 

Nickel-iron hydrogenases [NiFe] (Figure 8.2) are present in several bacteria. Their structure is known [22, 23] to be a heterodimeric protein formed by four subunits, three of which are small [Fe] and one contains the bimetallic active center consisting of a dimeric cluster formed by a six coordinated Fe linked to a pentacoordinated Ni (III) through two cysteine-S and a third ligand whose nature changes with the oxidation state of the metals in the reduced state it is a hydride, H, whereas in the oxidized state it may be either an oxo, 0, or a sulfide,... 

LiH+Hg=LiHg+iH2. The hydrides are strong reducing agents—the oxides of lead, copper, etc., are reduced to the metallic state. Lithium hydride slowly decomposes absolute alcohol, forming the alcoholate and hydrogen the hydrated alcohol is vigorously decomposed. The alkali hydrides are insoluble in ether and benzene. 

Organogermanium hydrides are very good reducing agents. In 1957, Anderson337 showed that Et3GeH reduced transition metal salts to their lower valence state (Cu11 to Cu1, Tilv to Tim or Tin, Vlv to Vm, CrIV to Cl ) or to the free metals (Au, Hg, Pd, Pt). 

The mechanism and stereochemistry of the reduction with metal hydride has been dealt with in many articles. It may be stated in general that the structure of the oxirane and the nature of the reducing agent exert great effects on the rate and pathway of the reaction. 

Oxidation and hydrolysis reactions are two common methods of producing oxide films. In this class of reaction, the metal precursor contains metal atoms in a reduced valence state, usually a metal hydride or metal halide. The oxidizing agent is an oxygen containing gas such as O2, O3, CO2, H2O, or N2O. The reaction is a simple oxidation scheme. Examples of such reactions are ... 

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