Metal complexes of saccharin

Metal complexes of the saccharinate anion, obtained by deprotonation of the N-H moiety of saccharin (o-sulfobenzimide) are reviewed. A wide variety of metal species based on mononuclear, binuclear, polynuclear complexes and extended coordination polymers are discussed in relation to the coordination modes of the anion, i.e., monodentate (through the N-atom or the carbonylic O-atom), bidentate, tridentate or bridge forming. The most important physicochemical properties, such as vibrational and electronic spectra, thermal, magnetic and redox properties as well as quantum chemical theoretical studies of these compounds are briefly described. With regard to saccharin in food and its health effects, the biological properties of saccharin and its complexes are also summarized. Finally, for comparative purposes, a brief overview on the so far characterized metallic complexes of thiosaccharin is given. This survey demonstrates that saccharinate is a very versatile and polyfunctional ligand in coordination chemistry. (c) 2005 Elsevier B.V. All rights reserved.