Stable gold(iii) complexes with thiosemicarbazone derivatives

Abstract

Novel thiosemicarbazonato complexes of gold(III) have been prepared from reactions of [Au(damp-C¹,N)Cl₂ (damp- = 2-(N,N-dimethylaminomethyl)phenyl) or [NBu₄][AuCl₄] with 2-pyridineformamide thiosemicarbazones (HL). The thiosemicarbazones deprotonate and coordinate as mononegative, tridentate NNS ligands to gold to give [Au(Hdamp-C¹)(L)]Cl₂ or [AuCl(L)]Cl complexes. The organometallic damp⁻ ligand is protonated during the reactions and the Au–N bond is cleaved. The [AuCl(L)]⁺ cations represent the first gold(III) complexes with thiourea derivatives which are not stabilised by an additional organometallic ligand. Reactions of [NBu₄][AuX₄] (X = Cl, Br) with diphenylthiocarbazone (dithizone) result in reduction of the metal and the formation of gold(I) complexes of the composition [AuX(SCN₄-3,4-Ph₂)] where SCN₄-3,4-Ph₂ is 3,4-diphenyltetrazole thione which is formed from cyclisation of dithizone.