On the geometry of the saccharinato ligand/ion in the metal saccharinates: Crystallographic survey and theoretical study

The structural data for the five-membered ring of unsubstituted saccharinato ligands/ions in saccharinates are retrieved from the Cambridge Structural Database and analyzed. The average geometries of saccharin and the corresponding deprotonated species in the solid state are obtained and the extreme cases of highly distorted structures are pointed out. The influence of the nature of the metal ion as well as of the type of the metal-to-saccharinato bonding on the saccharinato geometry is examined. On going from saccharin or covalent saccharinates to ionic ones the bonds adjacent to the nitranionic center are shortened, while the carbonyl and sulfonyl groups are simultaneously stretched. The value of the internal angle at the nitrogen atom is lowered and that at the sulfur atom is increased, causing bending of the angle between the sulfonyl oxygen atoms. The average geometries are reproduced well by several (semiempirical and ab initio) theoretical models.