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

Nine potentially S,N,Npy-tridentate thiosemicarba-zones (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-(CH3CN)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 [Re3Cl2(L23)(HL23)(CO)9]; and the thiosemicarbazonate compounds [Re(L)(CO)3], where the ligand is S,N,Npy-tridentate. Besides, the reaction in methanol or ethanol of the thiosemicarbazones derived from aldehydes yielded S,N,Npy-tridentate hemiaminal cationic [Re(HLOR)(CO)3]X and neutral [Re(LOMe)(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 NEt3 led to the formation of dinuclear [Re2(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.

Automated summary

Nine thiosemicarbazone ligands (HL) with S,N,Npy-tridentate coordination were synthesized and analyzed. Different types of compounds were obtained through the reactions of [ReX-(CH3CN)2(CO)3]/[ReX(CO)5] (X = Cl and Br) precursors with these ligands. The study also explored the influence of substituents on ligand stability and the effect of reaction medium on the resulting compounds.