Assessing Hypervalency in Iodanes.

The so-called hypervalent iodane compounds are very useful and versatile reactants and oxidizing agents in modern organic chemistry. The hypercoordinated central iodine in these compounds hints at a hypervalent state, which is often stressed to justify their reactivity. In this study a theoretical analysis of the electronic structure of a large, representative set of hypercoordinated iodane compounds has been carried out. We observed that the iodonium is not hypervalent in these compounds. In contrast, the analysis reveals a variation of the iodine valence state from a normal octet state to hypovalent depending on the ligands, but irrespective of the coordination number. On the basis of the calculations the reactivity of these compounds can be ascribed to the strong unquenched charge separation present in these molecules which represents a compromise between Coulomb interaction and the resistance of iodonium toward hypervalency. In extreme cases this leads to hypovalency and enhanced reactivity.