Q. Illustrate about Borohydrides?
Borohydrides like NaBH4,, Be(BH4,) 2 and Al(BH4)are the salts of complex tetrahydridoborate anion, BH-4,. Since in BH-4,. boron has a complete octet, the borohydrides are more stable than the boranes. Sodium borohydride is obtained by the reaction of NaH and methyl borate:
4NaH + B(OMe)3 ------------------------------------->NaBH4, + 3CH30Na
Other borohydrides are prepared from sodium borohydride. The alkali metal borohydrides are white, non-volatile, ionic solids which are stable in dry air. In contrast to the alkali metal borohydrides Be(BH4,)2, and Al(BH4,)3, are covalent and volatile in nature. The alkali metal borohydrides react with water with varying ease. Thus, LiBH4, reacts violently with water, KBH4, can be recrystallised from cold water while KBY, is even more stable.
LiBH4+ H2O --------------------------LiBO2 + 4H2