Synthesis, crystal structures and spectroscopic studies of diorganotin derivatives with mefenamic acid. Crystal and molecular structures of 1,2:3,4-di-μ2-2-[(2,3-dimethylphenyl)amino]-benzoato-O,O-1,3-bis-2-[(-[(2,3-dimethylphenyl)amino]benzoato-O-1,2,4:2

The complexes [Me2LSnOSnLMe2]2 (1) and [Bu2LSnOSnLBu2]2 (2) where HL is 2-[(2,3-dimethylphenyl)amino]benzoic acid (mefenamic acid), have been prepared and structurally characterized by means of 119Sn Mössbauer, vibrational and NMR (1H and 13C) spectroscopies. The crystal structures of complexes 1 and 2 have been determined by X-ray crystallography. Each structure is centro-symmetric and features a central rhombus Sn2O2 unit with two additional tin atoms linked at the O atoms. Pairs of tin atoms are bridged by bidentate carboxylate ligands and the ‘external’ tin atoms have their coordination geometry completed by a bridging bidentate carboxylate ligand for 1 and by a monodentate carboxylate ligand for 2. Five rings, each containing two tin atoms, are present in the dimeric tetraorganodistannoxane 1 and the geometry around the four tin centers is distorted octahedral for Sn(2) and Sn(2a) and trigonal bipyramidal for Sn(1) and Sn(1a). Three such rings are present in 2 and the geometry around the four five-coordinated tin centers, Sn(1), Sn(1a), Sn(2) and Sn(2a), is distorted square-bipyramidal. Significant π→π, CH→π stacking interactions and intramolecular hydrogen bonds stabilize structures 1 and 2. The polar imino hydrogen atom participates in intramolecular hydrogen bonds. Complexes 1 and 2 are self-assembled via π→π, CH→π and stacking interactions.