A Mechanochemical Route for the Synthesis of Diphenyleneiodonium Salts and the Estimation of Their Relative Solid-State Reactivities

Hypervalent halogen-containing compounds are recognized as green reagents for chemical synthesis. Iodonium (III) salts are regarded as the most beneficial classes of hypervalent halogen derivatives because of their advantageous reactivity and biological activities. A solvent-free, high-yielding, mechanochemical route is developed for the synthesis of diphenyleneiodonium (III) salts (DPI⁺X⁻). The optimal synthesis of several DPI salts, including triflate, mesylate, esylate, besylate, tosylate, and saccharinate, is reported in the study with high reaction yields. All reported salts are thoroughly characterized with the help of powder and single-crystal X-ray diffraction analysis. We also report the isolation of a new polymorph of DPI chloride salt, DPI-CHL2 which appears concomitantly with the known polymorph, DPI-CHL1. A optimized protocol for obtaining the pure bulk phases of the polymorphs is also presented in the study. We also performed a detailed computational analysis of the synthesized diphenyleneiodonium salts with the help of morphology predictions, and Hirshfeld surface analysis, to understand the effect of crystal morphology, crystal packing, and counterions on their solid-state reactivities. The reactivity comparison can help choose the most reactive DPI salts for further use as reagents or catalysts in mechanochemical solid-state reactions.