The cycloauration of pyridine-2-thiocarboxamide ligands

Abstract

Reactions of H[AuCl₄] with N-substituted 2-pyridine thiocarboxamide ligands 2-(C₅H₄N)C(S)NHR (R= p-C₆H₄Me, CH₂Ph, Me, p-C₆H₄OMe) gave cycloaurated derivatives {(C₅H₄N)C(S)NR}AuCl₂, with the ligand bonded as the thiol tautomer through the deprotonated SH group and the pyridine N atom to give a five-membered metallacyclic ring. The X-ray structure determination of the R = CH₂Ph derivative shows a square-planar gold(III) complex that dimerises in the solid state by weak Au...S intermolecular interactions. In contrast, in the reaction of H[AuCl₄] with 2-(C₅H₄N)C(S)NHR where R = 2-pyridyl, the ligand was oxidised to give a 1,2,4-thiadiazolo[2,3-a]pyridinium heterocyclic ring that was crystallographically characterised.