Fluoro and Trifluoromethyl Benzoyl Hypoiodite Complexes with Substituted Pyridines.

Based on the prior observation of the trifluoroacetate hypoiodite, CFC(O)OI, demonstrating the largest σ-hole of a neutral halogen bond donor, a series of mono- and bis-carbonyl hypoiodites utilising trifluoromethyl or fluorine substituents at various positions of a parent benzoyl skeleton have been synthesised. The carbonyl hypoiodite complexes were prepared via cation exchange of the silver(I) cations with iodine(I) from the respective silver(I) carboxylates and dicarboxylates as the synthetic precursors. A range of pyridinic Lewis bases of varying nucleophilicities were used to stabilise the carbonyl hypoiodites to further probe their properties. The silver(I) intermediates with these Lewis bases were also isolated for silver(I) pentafluorobenzoate, providing additional insight into the cation exchange reaction. All complexes were characterised both in solution (H, H-N HMBC, F) and in the solid state (SCXRD), permitting insights into the formation of the elusive pyridine-iodine(I) cation.