A series of cationic monodentate and bidentate
iodo(benz)imidazolium-based halogen bond (XB) donors were employed as
catalysts in a Mukaiyama aldol reaction. While 5 mol% of a monodentate variant
showed noticeable activity, a <i>syn</i>-preorganized
bidentate XB donor provided a strong performance even with 0.5 mol% loading. In
contrast to the very active BAr<sup>F</sup><sub>4</sub> salts, PF<sub>6</sub>
or OTf salts were either inactive or showed background reaction. Repetition
experiments clearly ruled out a potential hidden catalysis by elemental iodine
and demonstrated the stability of our catalyst over three consecutive cycles.
The influence of secondary interactions on the [N‐I‐N]+ halogen bond
