Solution Structure of Some λ~3 Iodanes: An ~(17)O NMR and DFT Study

摘要

The structure of a series of I—O bonded bis(acyloxy)iodoarenes and benzoiodoxolones in chloroform solution has been investigated by ~(17)O NMR spectroscopy and by density functional theory (DFT) calculations, employing the PBEO functional together with the LANL2DZ basis set extended with polarization (d) and diffuse (p) functions. This combined approach allowed us to ascertain that, although these classes of λ~3 iodanes maintain in chloroform solution their solid state "T-shaped" structure, a degenerate sigmatropic shift of iodine between the two oxygens of the acyloxy groups occurs in solution. The energy barrier involved in this process differs in the two classes, thus causing significant differences in the ~(17)O NMR spectra, at room temperature, of the two classes of compounds.