Mn(salen)-catalyzed sulfimidation: what are the real active species in sulfimidation?

An unusual temperature effect on enantioselectivity was found in a study of Mn(salen)-catalyzed sulfimidation. The phenomenon was considered to be attributable to the following reasons: the reaction of Mn(salen) and a nitrenoid precursor (ArINTs) provides primarily an Mn–ArINTs adduct which undergoes sulfimidation and transformation to an Mn–nitrenoid species competitively; however, the rates of sulfimidation by the Mn–ArINTs adduct and the Mn–nitrenoid species and of the transformation are dependent on the structure of the catalyst, the nature of ArINTs and the presence or absence of a donor ligand.