Write any two methods of preparation of diborane. How does it react with (i)Carbon monoxide and (ii)Ammonia ?

Explanation

(i)Preparation of diborane :
(i)Diborane can be prepared by treating `BF_3` with `LiAlH_4` in diethyl ether.
`4BF_3 + 3LiAlH_4 to 2B_2H_6 + 3LiF + 3AlF_3`
(2)In the laboratory it is conveniently prepared by the oxidation of sodium borohydride with iodine .
`2NaBH_4 +I_2 to B_2H_6 + 2NaI + H_2`
(3)On large scale it is prepared by reaction of `BF_3` with sodium hydride.
`2BF_3 +6NaOH overset"450 K"to B_2H_6 + NaF`
(ii)(a)Diborane forms addition product with CO with symmetric cleavage.
`B_2H_6 +2CO to 2BH_3 .CO`
(b)With ammonia it forms an addition product with asymmetric cleavage which on heating forms borazine which is known as inorganic benzene.
`2B_2H_6 + 6NH_3 to 3[BH_2(NH_3)_2]^(+) [BH_4]^(-) overset"heat"to 2B_3N_3H_6 + 12H_2`