Principles of supramolecular polymeric chain formation in heteronuclear gold(III)–iron(III) complexes ([Au(S₂CNR₂)₂][FeCl₄])_n (R = C₃H₇, iso-C₃H₇): Chemisorption synthesis, structural organization, and thermal behavior

Polymeric gold(III)–iron(III) dithiocarbamate–chloride complexes of the ionic type are synthesized by the chemisorption binding of gold(III) with freshly precipitated iron(III) dipropyl and di-iso-propyl dithiocarbamates from solutions of H[AuCl₄] in 2 M HCl. Heteropolynuclear complexes of the compositions ([Au{S₂CN(C₃H₇)₂}₂][FeCl₄])_n (I) and ([Au{S₂CN(iso-C₃H₇)₂}₂][FeCl₄])_n (II) are preparatively isolated as individual forms of gold(III) binding. The structural organization of the complexes is established by X-ray diffraction analysis (CIF files CCDC no. 1480802 (I) and no. 1480806 (II)). The structures of compounds I and II are characterized at the supramolecular level by the presence of two types of polymeric chains, the methods of formation of which differ substantially. Compound I contains the following structural units: four structurally nonequivalent centrosymmetric complex cations [Au{S₂CN(C₃H₇)₂}₂]⁺ (A, B, С, and D) and two complex anions [FeCl₄]^– related to each other as conformers. Two independent cation-cationic linear polymeric chains (···А···В···)_n and (···С···D···)_n are formed in the structure of complex I due to pair relatively weak secondary interactions Au···S (nonvalent type) between the adjacent complex cations. The structure of compound II is characterized by zigzag cation-anionic chains (···[Au{S₂CN(iso-C₃H₇)₂}₂]⁺···[FeCl₄]^–···)_n in the formation of which the secondary interactions Au···Cl play the determining role. The thermal behavior of complexes I and II is studied by simultaneous thermal analysis. The thermal destruction process includes the thermolysis of the dithiocarbamate moiety of the complexes and [FeCl₄]⁻ with the reduction of gold(III) to the metal, the liberation of FeCl₃, and the partial transformation of the latter into Fe₂O₃. In both cases, the final products of the thermal transformations of the studied compounds are elemental gold and Fe₂O₃.