Synthesis, characterization, crystal structures and in vitro antistaphylococcal activity of organotin(IV) derivatives with 5,7-disubstituted-1,2,4-triazolo[1,5-a]pyrimidine

Abstract

New organotin(IV) complexes of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl- 1,2,4-triazolo[1,5-a]pyrimidine (dptp) with 1:1 and/or 1:2 stoichiometry were synthesized and investigated by X-ray diffraction, FT-IR and 119Sn Mössbauer in the solid state and by 1H and 13C NMR spectroscopy, in so- lution. Moreover, the crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 are reported. The complexes contain hexacoordinated tin atoms: in Et2SnCl2(dbtp)2 two 5,7-ditertbutyl-1,2,4- triazolo[1,5-a]pyrimidine molecules coordinate classically the tin atom through N(3) atom and the coordina- tion around the tin atom shows a skew trapezoidal structure with axial ethyl groups. In Ph2SnCl2(EtOH)2 (dptp)2 two ethanol molecules coordinate tin through the oxygen atom and the 5,7-diphenyl-1,2,4-triazolo [1,5-a]pyrimidine molecules are not directly bound to the metal center but strictly H-bonded, through N (3), to the \OH group of the ethanol moieties; Ph2SnCl2(EtOH)2(dptp)2 has an all-trans structure and the C–Sn–C fragment is linear. On the basis of Mössbauer data, the 1:2 diorganotin(IV) complexes are advanced to have the same structure of Et2SnCl2(dbtp)2, while Me2SnCl2(dptp)2 to have a regular all-trans octahedral structure. A distorted cis-R2 trigonal bipyramidal structure is assigned to 1:1 diorganotin(IV) complexes. The in vitro antibacterial activities of the synthesized complexes have been tested against a group of reference pathogen micro-organisms and some of them resulted active with MIC values of 5 μg/mL, most of all against staphylococcal strains, which shows their inhibitory effect.