Synthesis and spectroscopic studies of diorganotin derivatives with tolfenamic acid. Crystal and molecular structure of the first complex of tolfenamic acid, 1,2 : 3,4-di-mu(2)-2-[(3-chloro-2-methylphenyl)amino]-benzoato-O,O-1,3-bis-2-[(3-chloro-2-methylphenyl)amino]-benzoato-O-1,2,4 : 2,3,4-di-mu(3)-oxo-tetrakis[di-n-butyltin(IV)]

The complexes [Me,LSnOSnLMe2](2) (1) [Bu2LSnOSnLBu2](2) (2) and Bu2SnL2.H2O (3), where HL is 2-[bis(3-chloro-2methylphenyl)amino]benzoic acid (tolfena mic acid), have been prepared and characterized structurally by means of Sn -19 Mossbauer, vibrational and H-1- and C-13-NMR spectroscopies. The crysta l structure of complex 2 has been determined by X-ray crystallography. Thre e distannoxane rings are present to the dimeric tetraorganodistannoxanes of planar ladder arrangement with distorted trigonal-bipyramidal geometry abo ut the five-coordinated tin centers. The structure, which has twofold symme try, features a central Sn2O2 unit with two additional tin atoms linked at O. Pairs of tin atoms are bridged by bidentate carboxylate ligands and the external tin atoms have their coordination geometry completed by a monodent ate carboxylate ligand. The tin atom geometries are similar and are based o n a trigonal bipyramidal arrangement. Significant pi --> pi stacking, C-H-p i interactions and intrarmolecular hydrogen bonds stabilize this structure. The polar imino hydrogen atom on N(1) and N(2) participate in a bifurcate intramolecular hydrogen bond. In this case complex 2 is self-assembled via C-H-pi and pi --> pi stacking interactions. Tin-119 Mossbauer, vibrational and NMR data are discussed in terms of the crystal structure and the propos ed structures for 1 and 3. From the variable-temperature Mossbauer effect, the Debye temperatures for 1-3 were determined. (C) 2001 Elsevier Science B .V. All rights reserved.