Search

Abstract: This review summarized the literature and own data on the parent organotin(IV) compounds and complexes formed with biologically active ligands. [Copyright &y& Elsevier]

Abstract: A number of [Ph3Sn(IV)]+ complexes formed with ligands containing –OH (–Cx2013;COOH group(s) and aromatic {N} donor atom have been prepared. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. In the complexes containing hydroxy and carboxylate functions, the carboxylato group is coordinated to the organotin(IV) centres in monodentate or bridging bidentate manner. It was also found that in the hydroxypyridine and -pyrimidine complexes the [Ph3Sn(IV)]+ moiety in most cases reacts with the phenolic form of the ligands. The rationalisation of the experimental 119Sn Mössbauer nuclear quadrupole splittings, |Δ exp| – according to the point charge model formalism – together with the FT-IR data support the formation of trigonal bipyramidal (Tbp) or octahedral (Oh) molecular structures. Furthermore, X-ray diffraction analysis has been performed on the triphenyltin(IV)-3-phenolato-2(1H)-pyridinone-O,O′ single crystals. The penta-coordinated tin center exhibits a Tbp geometry. In case of 2-picolinic acid, a trans-phenylation was observed during the complexation, resulting [Ph2Sn(IV)]2+ complex and Ph4Sn(IV). [Copyright &y& Elsevier]

Abstract: Nine complexes of tBu2Sn(IV)2+ were obtained in the solid state with ligands containing –COOH group(s) and aromatic {N} donor atom. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. It was found that in most cases the –COO− groups are co-ordinated in monodentate manner. Nevertheless, in some of our complexes, the –COO− group forms bridges between two central {Sn} atoms resulting in the formation of an oligomeric structure, a motif that is characteristic only to the nicotinate compound. These pieces of information and the rationalisation of the experimental 119Sn Mössbauer nuclear quadrupole splittings, Δ, – according to the point charge model formalism – support the formation of octahedral (Oh) or trigonal bipyramidal (TBP) molecular structures. The X-ray diffraction analysis of one complex obtained as single crystal revealed the distortion of the TBP geometry towards square pyramidal (SP) one. This was rationalised by PM3 molecular modelling of the tBu2Sn(pdc) complex. In the asymmetric unit, the two chemically similar but symmetry independent molecules form pseudo-dimers, in which the Sn⋯Sn separation amounts to ca. 6.4 Å. The crystal lattice is stabilised by C–H⋯O hydrogen bonding between individual molecules. [Copyright &y& Elsevier]

The coordination of Me2Sn(IV)2+ (&z.dbnd6;M) to captopril {N-[(S)-3-mercapto-2-methylpropionyl]-l-proline, &z.dbnd6;H2(cap), H2L} in aqueous solution was studied by means of potentiometric titration, electrospray mass spectrometry, 1H-NMR spectroscopy and Mo¨ssbauer spectroscopy in the pH range 2–11 (I=0.1 mol dm−3 NaClO4, 298 K). The results obtained with these methods proved that only monomeric complexes are formed in solution. In the acidic pH range, species with a metal-to-ligand ratio of 1:1 exist. The neutral complex ML, similarly to the complex Me2Sn(cap) crystallized in the same pH range, adopts a tbp structure with eq &z.sbnd;S− and ax &z.sbnd;COO−, while, instead of the coordination of the amide &z.sbnd;C&z.dbnd6;O, observed in the solid state, the other ax position is occupied by a H2O molecule. With increasing pH, in the neutral and weakly basic pH range the complexes MLH−1 and ML2 are formed, in which the &z.sbnd;COO− group is displaced from the coordination sphere by an OH− and an S− of another ligand, respectively. Biological activity tests on Me2Sn(cap) and three further R2Sn(IV) captopril complexes showed that n-Bu2Sn(cap) and t-Bu2Sn(cap) exert toxic activity towards the embryos of Ciona intestinalis, while the ligand itself does not affect the development of the embryos to any significant extent; Me2Sn(cap) and Et2Sn(cap) produced normal swimming larvae. [Copyright &y& Elsevier]