Alternatively, Pathway 2 suggested that the XB-donor interacts with the bromide anion generated from the uncatalysed heterolytic bond cleavage of the R-Br bond (Figure ). way 1 under the catalysis of CAT3 and CAT9 were remarkably similar (Figure and Table ). Despite both catalytic systems having the potential to bind in a bidentate manner, CAT9 displayed a preference for the monodentate binding mode (Figure ). This preference can be attributed to the tendency of the iodine atoms in CAT9 to orientate in opposite directions, as a result of geometric constraints (Figure and S5)).