Structural studies and bioactivity of diorganotin(IV) complexes of pyridin-2-thionato derivatives

Abstract

A series of diorganotin(IV) derivatives containing the potentially chelating S,N-ligands, 3-trifluoromethyl-pyridine-2-thione (3-CF3-pySH) and 5-trifluoromethyl-pyridine-2-thione (5-CF3-pySH), were prepared by direct reaction between the ligand and the corresponding diorganotin(IV) dichloride R2SnCl2 (R = Me, nBu, Ph) in the presence of triethylamine. The compounds have been characterized by microanalysis, mass spectrometry, IR spectroscopy and by 1H, 13C and 119Sn NMR spectroscopies. The crystal structures of compounds [Ph2Sn(3-CF3-pyS)2] (1) and [nBu2Sn(5-CF3-pyS)2] (2) were analyzed by X-ray diffraction. In both cases, the metal is in a bicapped tetrahedron environment, bound to two carbon atoms of the alkyl or aryl substituents and to the sulfur atoms and the heterocyclic nitrogen atoms of two pyridine-2-thionato ligands, which act as κ2-N,S chelating ligands. The supramolecular structure of 1 consists of chains of complexes parallel to the crystallographic b axis, built up by F⋯F, π-stacking and C–H⋯π intermolecular interactions. In the case of compound 2, the supramolecular structure is mainly determined by CH⋯F(CF3) intermolecular interactions that propagate along the crystallographic b axis. The antimicrobial activities of all complexes against S. aureus (MSSA and MRSA), A. baumanni, Aspergillus fumigates, Bacillus subtilis, E coli and Pseudomonas aeruginosa were also evaluated and in general the complexes derived from 5-trifluoromethylpyridine-2-thionate were found to be more active than the complex derived from 3-trifluoromethylpyridine-2-thionate.