Intermolecular hypervalent I(III)⋯O interactions: A new driving force for complexation of crown ethers

In this account, we show that intermolecular hypervalent I(III)⋯O interactions play an essential role in the complexation of organo-λ3-iodanes with crown ethers. In addition to the well-known driving force for the complexation of crown ethers, ion–dipole interaction, and hydrogen bonding interaction, our result provides a new class of interaction in supramolecular chemistry of crown ethers. Both solid state structure analysis and solution chemistry indicate that diaryl-, 1-alkynyl(phenyl)-, and 1-alkenyl(phenyl)-λ3-iodanes as well as 1-alkynyl(aryl)-λ3-bromanes form stable complexes with 18-crown-6 through hypervalent I(III)⋯O or Br(III)⋯O interactions. In these complexes, hypervalent iodine(III) or bromine(III) atom contacts with the three adjacent oxygen atoms of 18-crown-6. The complexation not only increases the stability of these hypervalent compounds but also increases the solubility toward polar solvents. The highly labile, activated iodosylbenzene monomers were isolated as stable crystalline complexes by the coordination of 18-crown-6. These iodosylbenzene monomer complexes serve as versatile oxidizing agents, especially in water as a solvent.