Chemistry - Complete Pblock- Question with Solution | TestHub

The formation of stronger backbond ($3\mathrm{p}\to 2\mathrm{p}$overlap in$\mathrm{B}\mathrm{C}{\mathrm{l}}_3$and weaker$3\mathrm{p}\to 3\mathrm{p}$overlap in$\mathrm{A}\mathrm{l}\mathrm{C}{\mathrm{l}}_3$) reduces the electron deficiency of the central atom and thus dimerisation tendency is reduced. So$\mathrm{A}\mathrm{l}\mathrm{C}{\mathrm{l}}_3$can form a dimer but$\mathrm{B}{\mathrm{F}}_3$and$\mathrm{B}\mathrm{C}{\mathrm{l}}_3$cannot.