Preparation, supramolecular self-organization and thermal behavior of polymeric complex of composition ([Au{S2CN(C3H7)2}2]3[Bi3Cl12]) n with unusual geometry of bismuth(III) complex anion

Abstract

A reaction of freshly precipitated bismuth(III) N,N-dipropyldithiocarbamate (PDtc) with AuCl3 solution in 2 M HCl was studied. A heteropolynuclear gold(III)-bismuth complex of ionic type [Au{S2CN(C3H7)2}2]3[Bi3Cl12] (I) was isolated by crystallization of products of the heterogeneous reaction from acetone-chloroform (1: 1) solution. Crystal and supramolecular structure of compound I established by X-ray diffraction study includes structurally nonequivalent complex cations [Au{S2CN(C3H7)2}2]+ related to each other as conformers (hereinafter cations A, B, C, and D) in 1: 1: 2: 2 ratio. Due to secondary Au⋯S bonds (3.386–3.617 A), the isomeric cations form trinuclear species of two types: [C⋯A⋯C] and [D⋯B⋯D] that differ in the character of intercationic binding and Au-Au distances. Relatively weak aurophilic Au⋯Au bonds (3.4704(3) A) unite the neighboring cationic triads into zigzag polymeric chains of type (⋯[C⋯A⋯C]⋯[D⋯B⋯D]⋯)n oriented along the crystallographic axis b. The spatial isolation of neighboring chains is provided by discrete trinuclear anions [Bi3Cl12]3− where metal atoms bind four bridging (μ2 and μ3) chlorine atoms, while each bismuth atom forms distorted octahedral chromophore [BiCl6]. The complex tribismuth anion in the structure I is the first example of [Bi3Cl12]3− anion of angle rather than linear structure: Bi(1)Bi(2)Bi(3) angle is 72.358°. The thermal behavior of compound I was studied by simultaneous thermal analysis. The multistage process of thermal destruction includes the thermolysis of dithiocarbamate portion of the complex and [Bi3Cl12]3− accompanied by reduction of gold(III) to metal and release of BiCl3 (followed by its evaporation) and partial formation of Bi2S3. In the temperature range 680–760°C, bismuth sulfide undergoes oxidation to (BiO)2SO4, which decomposes above 760°C to give Bi2O3. Residue after thermolysis of compound I is gold metal and bismuth(III) oxide.