Tetrahydridogallate

Shriver, The Manipulation of Air-Sensitive Compounds, Chap. 7, McGraw-Hill Book Company, New York, 1969. 

Rendle, A. Storr, and J. Trotter, J. Chem. Soc., Dalton Trans., 1973, 2252, and references therein. 

Lithium tetrahydridogallate, which was first prepared by Finholt, Bond, and Schlesinger,1 is a very useful starting material for the preparation of gallium hydride derivatives.2-3 The present synthesis is based on an adaptation of the original preparation.1-4 Since gallium-hydrogen bonds are susceptible to hydrolysis, it is necessary to perform the preparation in the absence of air. The procedure described is based on the use of Schlenk-type inert-atmosphere techniques. 

In a 50-mL Schlenk flask equipped with a magnetic stirring bar are placed 1.32 g finely powdered lithium hydride (0.166 mol)t and 10 mL of dry, freshly distilled diethyl ether. A dropping funnel equipped with a Teflon-in-glass valve and containing 1.77 ggallium(III) chloride (0.010 mol) in 10 mL of dry, freshly distilled diethyl ether (dissolution is exothermic) is fitted to the Schlenk flask and the outlet arms are linked as illustrated in Fig. 10 to equalize pressure. 

The LiH-(C2H5)20 slurry is cooled to 0° to moderate the ensuing reaction with gallium(III) chloride, and the latter solution is added dropwise with stirring over a 1-hr period. The reaction mixture is then warmed to room temperature and stirred for 5 hr. A 10-mL portion of dry toluene is 

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Lithium tetrahydridogallate(l —) is a moisture-sentitive solid similar in many respects to lithium tetrahydridoaluminate(l —). It reacts with protic solvents, but is soluble without reaction in a variety of ethers. The solid decomposes slowly at room temperature, but may be stored with decomposition at — 78° under an inert atmosphere or in vacuum. Ether solutions are stable for at least several days. A variety of gallium hydride derivatives may be prepared from Li[GaH4], including (CH3)3N GaH3.1,2,6 Infrared and Raman data have been reported for [GaH4]-.7... 

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