Question

Is ever $ {[AlC{l_4}]^ - } $ possible?
 $ A) $ True
 $ B) $ False

Answer 1

Hint : $ AlC{l_3} $ is a Lewis acid, electron deficient. It is widely used as catalyst for the halogenation of aromatic groups, also used as a catalyst in Friedel crafts alkylation and acylation reactions. Many other organic reactions also use it as a catalyst. It is a major industrial catalyst.

Complete Step By Step Answer:
Aluminium $ (Al) $ forms aluminium chloride $ \left( {AlC{l_3}} \right) $ , where the hybridisation of Al is $ s{p^2} $ having a vacant p-orbital. $ AlC{l_3} $ is electron deficient acting as Lewis acid.
Chloride ion $ \left( {C{l^{ - 1}}} \right) $ has lone pairs of electrons, and can act as electron donors. When it reacts with $ AlC{l_3} $ it forms $ {[AlC{l_4}]^ - } $ . We can say that $ AlC{l_3} $ can form tetrachloroaluminate $ {[AlC{l_4}]^ - } $ in the presence of chloride ions.
Thus, we have seen that $ {[AlC{l_4}]^ - } $ is possible.
The answer to our question is:
 $ A) $ True
 $ {[AlC{l_4}]^ - } $ is possible. It is formed as an intermediate in the Friedel crafts of alkylation and acylation. In these reactions Aluminium trichloride is used as a catalyst which during the course of the reaction forms $ {[AlC{l_4}]^ - } $ .

Additional Information:
Aluminium tetrachloride $ {[AlC{l_4}]^ - } $ anion has a tetrahedral shape just like carbon tetrachloride. These aluminium tetrachlorides are soluble in many organic solvents, creating an ionic non-aqueous solution. These are suitable components of electrolytes for batteries. Lithium tetrachloroaluminate is used in some lithium batteries.

Note :
We have seen that Aluminium tetrachloride ion is possible and is formed as intermediate in organic reactions. Aluminium trichloride is formed from aluminium trichloride . $ AlC{l_3} $ is in white colour but sometimes it acquires yellow colour due to the presence of contaminants. Solid aluminium chloride $ AlC{l_3} $ is covalently bonded with low melting point and boiling point.