Crystal structures of seven mixed-valence gold compounds of the form [(<i>R</i> ¹ <i>R</i> ² <i>R</i> ³P<i>E</i>)₂Au^I]⁺[Au^III <i>X</i> ₄]⁻ (<i>R</i> =

During our studies of the oxidation of gold(I) complexes of tri-alkyl-phosphane chalcogenides, general formula <i>R</i> ¹ <i>R</i> ² <i>R</i> ³P<i>E</i>Au<i>X</i>, (<i>R</i> = <i>tert</i>-butyl or isopropyl, <i>E</i> = S or Se, <i>X</i> = Cl or Br) with PhICl₂ or elemental bromine, we have isolated a set of seven mixed-valence by-products, the bis-(tri-alkyl-phosphane chalcogenido)gold(I) tetra-halogenidoaurates(III) [(<i>R</i> ¹ <i>R</i> ² <i>R</i> ³P<i>E</i>)₂Au]⁺[Au<i>X</i> ₄]^-. These corres-pond to the addition of one halogen atom per gold atom of the Au^I precursor. Com-pound <b>1</b>, bis-(triiso-propyl-phosphane sulfide)-gold(I) tetra-chlorido-aur-ate(III), [Au(C₉H₂₁PS)₂][AuCl₄] or [( ^<i>i</i> Pr₃PS)₂Au][AuCl₄], crystallizes in space group <i>P</i>2₁/<i>n</i> with <i>Z</i> = 4; the gold(I) atoms of the two cations lie on twofold rotation axes, and the gold(III) atoms of the two anions lie on inversion centres. Compound <b>2</b>, bis-(<i>tert</i>-butyl-diiso-propyl-phosphane sulfide)-gold(I) tetra-chlorido-aurate(III), [Au(C₁₀H₂₃PS)₂][AuCl₄] or [( ^<i>t</i> Bu ^<i>i</i> Pr₂PS)₂Au][AuCl₄], crystallizes in space group <i>P</i>1 with <i>Z</i> = 4; the asymmetric unit contains two cations and two anions with no imposed symmetry. A least-squares fit of the two cations gave an r.m.s. deviation of 0.19 Å. Compound <b>3</b>, bis-(tri-<i>tert</i>-butyl-phosphane sulfide)-gold(I) tetra-chlorido-aurate(III), [Au(C₁₂H₂₇PS)₂][AuCl₄] or [( ^<i>t</i> Bu₃PS)₂Au][AuCl₄], crystallizes in space group <i>P</i>1 with <i>Z</i> = 1; both gold atoms lie on inversion centres. Compound <b>4a</b>, bis-(<i>tert</i>-butyl-diiso-propyl-phosphane sulfide)-gold(I) tetra-bromi-doaurate(III), [Au(C₁₀H₂₃PS)₂][AuBr₄] or [( ^<i>t</i> Bu ^<i>i</i> Pr₂PS)₂Au][AuBr₄], crystallizes in space group <i>P</i>2₁/<i>c</i> with <i>Z</i> = 4; the cation lies on a general position, whereas the gold(III) atoms of the two anions lie on inversion centres. Compound <b>4b</b>, bis-(<i>tert</i>-butyl-diiso-propyl-phosphane selenide)gold(I) tetra-bromido-aurate(III), [Au(C₁₀H₂₃PSe)₂][AuBr₄] or [( ^<i>t</i> Bu ^<i>i</i> Pr₂PSe)₂Au][AuBr₄], is isotypic with <b>4a</b>. Compound <b>5a</b>, bis-(tri-<i>tert</i>-butyl-phosphane sulfide)-gold(I) tetra-bromido-aurate(III), [Au(C₁₂H₂₇PS)₂][AuBr₄] or [( ^<i>t</i> Bu₃PS)₂Au][AuBr₄], is isotypic with compound <b>4a</b>. Compound <b>5a</b>, bis-(tri-<i>tert</i>-butyl-phosphane sulfide)-gold(I) tetra-bromido-aurate(III), [Au(C₁₂H₂₇PS)₂][AuBr₄] or [( ^<i>t</i> Bu₃PS)₂Au][AuBr₄], crystallizes in space group <i>P</i>1 with <i>Z</i> = 1; both gold atoms lie on inversion centres. Compound <b>5b</b>, bis-(tri-<i>tert</i>-butyl-phosphane selenide)gold(I) tetra-bromido-aurate(III), [Au(C₁₂H₂₇PSe)₂][AuBr₄] or [( ^<i>t</i> Bu₃PSe)₂Au][AuBr₄], is isotypic with <b>5a</b>. All Au^I atoms are linearly coordinated and all Au^III atoms exhibit a square-planar coordination environment. The ligands at the Au^I atoms are anti-periplanar to each other across the S⋯S vectors. There are several short intra-molecular H⋯Au and H⋯<i>E</i> contacts. Average bond lengths (Å) are: P-S = 2.0322, P-Se = 2.1933, S-Au = 2.2915, and Se-Au = 2.4037. The complex three-dimensional packing of <b>1</b> involves two short C-H_methine⋯Cl contacts (and some slightly longer contacts). For <b>2</b>, four C-H_methine⋯Cl inter-actions combine to produce zigzag chains of residues parallel to the <i>c</i> axis. Additionally, an S⋯Cl contact is observed that might qualify as a 'chalcogen bond'. The packing of <b>3</b> is three-dimensional, but can be broken down into two layer structures, each involving an S⋯Cl and an H⋯Cl contact. For the bromido derivatives <b>4a</b>/<b>b</b> and <b>5a</b>/<b>b</b>, loose associations of the anions form part of the packing patterns. For all four compounds, these combine with an <i>E</i>⋯Br contact to form layers parallel to the <i>ab</i> plane.