Gold complexes with thiosemicarbazones: reactions of bi- and tridentate thiosemicarbazones with dichloro[2-(dimethylaminomethyl)phenyl-C1,N]gold(III), [Au(damp-C1,N)Cl2]

Abstract

Dichloro[2-(N,N-dimethylaminomethyl)phenyl-C¹,N]gold(III), [Au(damp-C¹,N)Cl₂] (1), reacts with salicylaldehyde thiosemicarbazone (H₂saltsc), vanilline thiosemicarbazone (Hvantsc), N-methylpyrrole aldehyde thiosemicarbazone (Hmepyrtsc), pyridoxal methylthiosemicarbazone (H₂pydoxmetsc), 2-diphenylphosphinobenzaldehyde thiosemicarbazone (HPtsc) or variously substituted acetylpyridine thiosemicarbazones (HapRtsc; R = H, Me, Ph) with cleavage of the Au–N bond and protonation of the dimethylamino group. Compounds of general formulae [Au(Hdamp-C¹)Cl(L)]⁺ (L = Hsaltsc⁻, vantsc⁻, mepyrtsc⁻), [Au(Hdamp-C¹)Cl(L)]²⁺ (L = H₂pydoxmetsc) or [Au(Hdamp-C¹)(L)]²⁺ (L = Ptsc⁻, apRtsc⁻, R = H, Me, Ph) have been isolated and characterized. The presence of the σ-bonded 2-(dimethylaminomethyl)phenyl ligand is mandatory to prevent reduction of the gold(III) centre. The crystal structures of [Au(Hdamp-C¹)Cl(Hsaltsc)](PF₆) (3a), [Au(Hdamp-C¹)Cl(mepyrtsc)]Cl (3c), [Au(Hdamp-C¹)Cl(H₂pydoxmetsc)]Cl₂·MeOH (4), [Au(Hdamp-C¹)(apPhtsc)]Cl₂·2 MeOH (5c) and [Au(Hdamp-C¹)(Ptsc)]Cl₂· 1.5MeOH (6) have been elucidated, showing the gold atoms in distorted square-planar co-ordination environments.

The potentially O,N,S-tridentate ligands H₂saltsc and H₂pydoxmetsc co-ordinate in a bidentate fashion and do not incorporate the OH groups in the chelating framework, whereas HapRtsc or HPtsc co-ordinate in a tridentate manner. Generally, one or more hydrogen atoms of the heterocyclic ligands and/or the NMe₂H⁺ group form hydrogen bridges in the solid state structures. The preliminary results of antiproliferation tests on tumor cells demonstrate the considerable cytotoxicity of these new gold complexes.

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