Question

Is BI3 a stronger Lewis acid than BCl3 and BF3?

Answer 1

Perhaps...

Explanation:

`BBr_3` is the STRONGEST LEWIS ACID known experimentally. Why so, given that bromine is LESS electronegative than fluorine and chlorine?

Well the lone pair electrons on the bound bromine are diffuse, and not dense, and are therefore less competent to donate electron density to the empty p-orbital on boron.