Triorganotin(IV) derivatives of 7-amino-2-(methylthio)[1,2,4]triazolo [1,5-a]pyrimidine-6-carboxylic acid. Synthesis, spectroscopic characterization, in vitro antimicrobial activity and X-ray crystallography

Triorganotin(IV) complexes of the 7-amino-2-(methylthio)[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylic acid (HL), Me3SnL(H2O), (1), [n-Bu3SnL]2(H2O), (2), Ph3SnL(MeOH), (3), were synthesized by reacting the amino acid with organotin(IV) hydroxides or oxides in refluxing methanol. The complexes have been characterized by elemental analysis, 1H, 13C and 119Sn NMR, IR, Raman and 119Sn Mössbauer spectroscopic techniques. Single crystal X-ray diffraction data were obtained for compounds (2) and (3). Ph3SnL(MeOH) presents a trigonal bipyramidal structure with the organic groups on the equatorial plane and the axial positions occupied by a ligand molecule, coordinated to tin through the carboxylate, and a solvent molecule, MeOH. A similar structure is proposed for Me3SnL(H2O) on the basis of analytical and spectroscopic data. The tributyltin(IV) derivative, [n-Bu3SnL]2(H2O), is characterized by two different tin sites with similar tbp geometry featured by butyl groups on the equatorial plane. Sn(1) and Sn(2) atoms are axially bridged by a ligand molecule binding through the N(4) and the carboxylate group; the two coordination spheres are saturated by another ligand molecule, binding the metal through the carboxylate group, and a water molecule, respectively. Antimicrobial tests on compounds 1 and 2 showed in vitro activity against Gram-positive bacteria.