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

Abstract

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.