Reduction reactions with gallium compounds

The Group 13 dichlorides of formula Ar MCb [AT = 8-(dimethylamino)-l-naphthyl M = Al, Ga or In) have been prepared by the salt elimination reaction of one equivalent of Ar Li with MCI3 in toluene solution at -78 °C. The X-ray crystal structures show that the aluminium and gallium compounds are monomeric while the indium compound is dimeric. Reduction of the aluminium monomer with LiAlH4 gives the dimeric dihydride [Ar AlH2]2. There has been a report of the first structurally characterised aluminium compounds with terminal acetylide groups (24, 25). ... 

The equilibrium levels of the reaction products are very small, but both can dissolve in liquid sodium, and sodium oxide can form compounds with silica. As a consequence, the reaction moves to the right, leading to further reduction of silica. Nevertheless, vitreous silica crucibles have been used sucessfully for containing molten antimony (850°C), copper (1 210°C), gallium (1 100°C), germanium (1 100°C), lead (500°C) and tin (900 C). 

The tetrahedral cluster compounds can be synthesized by three methods (1) reaction of the monohalides EX (X = Cl, Br, I) with alkyllithium or Grignard reagents, (2) reduction of suitable organoelement halides of trivalent aluminum, gallium or indium, and (3) thermolysis of R2E-ER2 compounds. 

In chemical vapour deposition a mixture of the gaseous reactants is passed over a solid surface, under such conditions that the reaction will take place at the surface only. Well known examples are reactions for the formation of epitaxial silicon, e.g., by reduction of silicon tetrachloride with hydrogen, or by the decomposition of silane (silicium hydride). Also semiconductor compounds such as gallium arsenide and indium phosphide are produced in a similar manner. This is a very specialized area, a description of which is outside the scope of this book. Nevertheless, chemical vapour deposition is an interesting principle for manufacturing solid materials that might find broader application, so that a brief introduction may be useful here. 

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