Gold(III)–iron(III) heteropolynuclear complexes ([Au{S2CNR2}2][FeCl4])n (R = C4H9, iso-C4H9): Chemisorption synthesis, supramolecular self-organization, and thermal behavior

Abstract

The reactions of iron(III) dibutyl and di-iso-butyl dithiocarbamates [Fe(S₂CNR₂)₃] (R = C₄H₉, iso-C₄H₉) with anions [AuCl₄]^– in 2 M HCl are studied. The result of heterogeneous reactions of gold(III) chemisorption binding from a solution is the formation of gold(III)–iron(III) heteropolynuclear complexes of the ionic type. The crystal and supramolecular structures of polymer complexes ([Au{S₂CN(C₄H₉)₂}₂][FeCl₄])_n (I) and ([Au{S₂CN(iso-C₄H₉)₂}₂][FeCl₄])_n (II) are determined by X-ray diffraction analysis (CIF files CCDC 1407704 (I) and 1407802 (II)). The structure of complex I contains two centrosymmetrical structurally nonequivalent complex cations [AuS{₂CN(C₄H₉)₂}₂]⁺ (A and B) and complex anion [FeCl₄]^–. Structure II is formed by three isomeric complex cations [Au{S₂CN(iso-C₄H₉)₂}₂]⁺ (А, В, and С) and two anions [FeCl₄]^– related as conformers. The isomeric cations are involved in the formation of linear (…А…В…)_n (in I) or zigzag (…А…В…А…С…)_n (in II) polymer chains due to pairs of weak secondary interactions Au···S. The thermal behavior of the complexes is studied by simultaneous thermal analysis. Thermal destruction includes the thermolysis of the dithiocarbamate moiety of the complexes and anions [FeCl₄]^– with the reduction of gold(III), release of FeCl3, and partial formation of Fe₂O₃. The final thermolysis products are metallic gold and Fe₂O₃.