"One-step" synthesis of nonsolvated aluminum hydride

The direct reaction of lithium tetrahydroaluminate with aluminum chloride in an ether-toluene mixture at temperatures >= 90 degrees C was studied. Under these conditions, nonsolvated aluminum hydride is formed in a yield >= 80%. The product formed represents agglomerates with the highly developed surface and has satisfactory hydrolytic and thermal stability but an increased lithium chloride content (0.25-2.2 wt.%). The decrease in the percentage of this impurity to 0.2 wt.% is achieved by using chloroalanes AlH(3-n)Cl(n)center dot xOEt(2) (n <= 1) instead of aluminum chloride along with vigorous stirring and an increase in the synthesis-crystallization temperature to >= 100 degrees C. The use of compounds based on magnesium tetrahydroaluminate, LiAlH(4)center dot Mg(AlH(4))(2) or LiCl center dot Mg(AlH(4))(2), as modifying agents increases the thermal stability of the hydride and decreases the agglomeration of the crystals.