The Chloroazaphosphatrane Motif for Halogen Bonding in Solution.

Chloroazaphosphatranes, the corresponding halogenophosphonium cations of the Verkade superbases, were evaluated as a new motif for halogen bonding (XB). Their modulable synthesis allowed for synthetizing chloroazaphosphatranes with various substituents on the nitrogen atoms. The binding constants determined from NMR titration experiments for Cl, Br, I, AcO, and CN anions are comparable to those obtained with conventional iodine-based monodentate XB receptors.