The effect of the rcation/ranion ratio on the structural and chemical properties of N-chloroarenesulfonamidates

A comparative structural study on sodium and potassium N-chloroarenesulfonamidates has been carried out using X-ray diffraction and IR spectroscopy as experimental techniques. As shown by crystallographic studies, the sodium ions tend to incorporate more water oxygen atoms in their coordination spheres than the potassium ions, while the potassium congeners prefer the interaction with sulfonamidate moieties. The marked dissimilarity between the compositions of the coordination spheres as well as the different tendency of the sodium and potassium salts to absorb moisture from the air have been attributed to the different sizes of the sodium and potassium ions. The opposite shifts of the νas(SO2) and ν(SN) bands upon dehydration have been ascribed to an increased polarization of the sulfonyl group by the metal centers. Based on IR spectroscopic observations, a weakening of the N–Cl bonds is suspected in the water-free compounds, which may contribute to the known thermal instability of the dehydrated salts of N-chloroarenesulfonamides. Various sections of IR spectra as well as X-ray powder diffraction patterns have proved to be suitable to identify the water-free and hydrated samples.

The dissimilar composition of the Na and K coordination spheres and the different propensity of the sodium and potassium N-chloroarenesulfonamidates toward rehydration have been interpreted in terms of different radius ratios of the cation to the anion in the Na and K counterparts. The organic ligand in C6H5SO2NClK · H2O displays a unique chelating coordination mode of the sulfonamidate moiety.Figure optionsDownload as PowerPoint slide