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-carboxylicacid (HL), Me3SnL(H2O), (1), [n-Bu3SnL]2(H2O), (2), Ph3SnL(MeOH), (3), were synthesized by reacting theamino acid with organotin(IV) hydroxides or oxides in refluxing methanol. The complexes have been characterizedby elemental analysis, 1H, 13C and 119Sn NMR, IR, Raman and 119Sn Mössbauer spectroscopictechniques. 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 axialpositions 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 spectroscopicdata. The tributyltin(IV) derivative, [n-Bu3SnL]2(H2O), is characterized by two different tin sites with similartbp geometry featured by butyl groups on the equatorial plane. Sn(1) and Sn(2) atoms are axiallybridged by a ligand molecule binding through the N(4) and the carboxylate group; the two coordinationspheres are saturated by another ligand molecule, binding the metal through the carboxylate group, and awater molecule, respectively. Antimicrobial tests on compounds 1 and 2 showed in vitro activity againstGram-positive bacteria.