The structure of aluminium bromide is best represented as :

Which reactions can be used to prepare diborane

$I.\,\,NaBH_4 + BF_3$ (in ether) $\to $

$II.\,\, NaBH_4 + I_2 \to $

$III.\,\, BF_3 + NaH \to $

Anhydrous $AlCl_3$ is formed in

Hydrated $AlCl_3$ is used as :

Aluminium chloride exists as a dimer, $Al_2Cl_6,$ in solid state as well as in solution of non-polar solvents such as benzene. When dissolved in water, it gives:

${H_3}B{O_3}\,\xrightarrow{{{T_1}}}X\,\xrightarrow{{{T_2}}}Y\,\xrightarrow{{\operatorname{Re} d\,\,\,hot}}{B_2}{O_3}$

if $T_1 < T_2$ then $X$ and $Y$ respectively are