Coordination Chemistry of Potentially S,N,N(py)-Tridentate Thiosemicarbazones with the {Re(CO)(3)}(+) Fragment and Formation of Hemiaminal Derivatives

[Image: see text] Nine potentially S,N,N(py)-tridentate thiosemicarbazones (HL) derived from pyridine-2-carbaldehyde or 1-(2-pyridyl)ethanone have been prepared and fully characterized. The X-ray crystal structures of six of them and two hydrochlorides were determined and analyzed. The reaction of the [ReX(CH(3)CN)(2)(CO)(3)]/[ReX(CO)(5)] (X = Cl and Br) precursors with these ligands yielded different kinds of compounds: the adducts [ReX(HL)(CO)(3)], in which the ligands were S,N-bidentate; the trinuclear species [Re(3)Cl(2)(L(23))(HL(23))(CO)(9)]; and the thiosemicarbazonate compounds [Re(L)(CO)(3)], where the ligand is S,N,N(py)-tridentate. Besides, the reaction in methanol or ethanol of the thiosemicarbazones derived from aldehydes yielded S,N,N(py)-tridentate hemiaminal cationic [Re(HL(OR))(CO)(3)]X and neutral [Re(L(OMe))(CO)(3)] complexes after the coordinated ligand underwent addition of the alcohol group to the imine bond. The reactivity of the complex [ReX(HL)(CO)(3)] in MeOH and NEt(3) led to the formation of dinuclear [Re(2)(L)(2)(CO)(6)], where the thiosemicarbazonate is again S,N-bidentate. The influence that the substituents on the thiosemicarbazone ligands have on the stability of the complexes and the effect of the reaction medium on the resulting compounds have been analyzed.