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.