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[Bis(pyridine)iodine(I)]+ complexes offer controlled access to halonium ions under mild conditions. The reactivity of such stabilized halonium ions is primarily determined by their three‐center, four‐electron [N−I−N]+ halogen bond. We studied the importance of chelation, strain, steric hindrance and electrostatic interaction for the structure and reactivity of halogen bonded halonium ions by acquiring their 15N NMR coordination shifts and measuring their iodenium release rates, and interpreted the data with the support of DFT computations. A bidentate ligand stabilizes the [N−I−N]+ halogen bond, decreasing the halenium transfer rate. Strain weakens the bond and accordingly increases the release rate. Remote modifications in the backbone do not influence the stability as long as the effect is entirely steric. Incorporating an electron‐rich moiety close by the [N−I−N]+ motif increases the iodenium release rate. The analysis of the iodine(I) transfer mechanism highlights the impact of secondary interactions, and may provide a handle on the induction of stereoselectivity in electrophilic halogenations., Halogen bond‐stabilized halonium ions are mild halenium transfer agents. The dependence of their reactivity on chelation, strain, steric hindrance and electrostatic interaction has been evaluated using NMR, DFT and kinetics experiments. The mechanistic analysis of the transfer is expected to provide a handle in the induction of stereoselectivity in electrophilic halogenations.

A series of arylene ethynylene compounds has been generated in order to study the differences between strong and weak intramolecular halogen bonding in solution. With strong intramolecular halogen bonding, the presence of electron withdrawing fluorine substituents near the halogen bond donor has a significant impact on the halogen bond and consequently on ¹³C NMR chemical shifts. UV-vis studies suggest increased conjugation of the arylene ethynylene backbone when strong halogen bonds are present. UV-vis and NMR signatures of intramolecular halogen bonding are diminished significantly when electron withdrawing fluorine substituents are absent, however. This change in behavior is further illustrated by differences in crystallization tendencies with the presence or absence of electron withdrawing substituents. Calculations using the M06-2X functional provide some insight into the energies associated with both strong and weak intramolecular halogen bonding.