EDA Complexes of N-halosaccharins with N- and O-donor ligands

A series of EDA complexes of N-iodosaccharin (NISac) and N-bromosaccharin (NBSac) with nitrogen and oxygen electron-pair donors, NISac·H₂O, NISac·THF, NISac·Py, NISac₂·Pyz and NBSac₂·Pyz, was prepared and examined by X-ray diffraction and NMR. The complexes are relatively stable, crystalline compounds with the ligand bound to the halogen atom in a nearly linear arrangement N–halogen–ligand. The halogen–ligand distances are inversely proportional to the donor ability of the ligand. The interactions between ligand and halogen are stronger for iodine than bromine. The X-ray structure analysis has shown that for some compounds the N–X bond in the halosaccharin moiety is not coplanar with the isothiazole ring, and the quantum-chemical calculations demonstrate a high flexibility of the corresponding angle. Complexes were modelled also by DFT calculations using B3LYP and MPW1K functionals. A better fit of the computed geometry was obtained by the geometry optimization in a polar solvent continuum than in vacuum.