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.