Q. Extensive chemistry of the boron hydrides?
The extensive chemistry of the boron hydrides finds no parallel with the hydrides of heavier elements of Group 13. Out of the four possible binary hydrides of Al, Ga, In and TI, only aluminium hydride, (AlH3,),, is known. It is prepared by the action of either 10O0% pure H2S04 or AlCI3 on lithium aluminium hydride in fin ethereal solvent:
2LiAIH4 + H2S04 -------------------------> 2/n (AIH3)n, + Li2SO4, + 2H2
3LiAIH4 + AICl3---------------------------> 4/n(AIH3)N + 3LiCl
Aluminium hydride is a colourless non-volatile thermally unstable (above 425K) solid. It is a strong reducing agent and reacts violently with water and other protic reagent to liberate H2.
2(A1H3)n, + 6nH20------------------> 2nAI(OH)3 + 9nH2
Similar to B2H2 (AlH3) is also an electron deficient compound. Therefore it is extensively polymerised by 3c- 2c non linear al- H- Al bonds.