Synthesis and crystal structures of a polymeric trimethyltin(IV) and a tetranuclear dibutyltin(IV) complex with azo-carboxylates derived from 4- or 3-amino benzoic acid and naphthalen-1 or 2-ol

Abstract

Complex 1 was synthesized by the reaction of 4-(4-hydroxynaphthylazo)-benzoic acid with trimethyltin(IV) chloride in anhydrous methanol using triethylamine as base while 2 was synthesized by the reaction of 3-(2-hydroxynaphthylazo)-benzoic acid with dibutyltin(IV) oxide in anhydrous toluene. The complexes were characterized by elemental analysis, IR, and multinuclear (1H, 13C, and 119Sn) NMR spectroscopy. The coordination behavior and geometries around tin in 1 and 2 were established by X-ray crystallography while geometries of the complexes in solution were determined by 119Sn-NMR spectroscopy. The polymeric 1 displayed slightly distorted trigonal bipyramidal geometry around the tin with the equatorial plane occupied by three methyl groups and the axial positions occupied by a carboxylate oxygen and a phenoxide oxygen of another ligand. The tetranuclear 2 exhibited a bis[dicarboxylatotetraorganodistannoxane] type structure with a non-centrosymmetric Sn2O4 core where the central Sn2O2 ring was connected to two exo-cyclic tin ions through μ3 -oxo atoms. The coordination geometry around exo- and endo-cyclic tin ions was distorted octahedral and deformed square pyramidal, respectively. 119Sn NMR spectral study suggested four-coordinate tetrahedral 1 while six- and five-coordinate structures around exo- and endo-cyclic tin ions for 2 in solution.