Crystal structures of seven mixed-valence gold compounds of the form [(R
1
R
2
R
3PE)2AuI]+[AuIII
X
4]− (R = tert-butyl or isopropyl, E = S or Se, and X = Cl or Br)
Authors: Upmann Daniel , Bockfeld Dirk , Jones Peter G. , Târcoveanu Eliza 
Published: September 2024

During our studies of the oxidation of gold(I) complexes of trialkylphosphane chalcogenides, general formula R
1
R
2
R
3PEAuX, (R = tert-butyl or isopropyl, E = S or Se, X = Cl or Br) with PhICl2 or elemental bromine, we have isolated a set of seven mixed-valence by-products, the bis(trialkylphosphane chalcogenido)gold(I) tetrahalogenidoaurates(III) [(R
1
R
2
R
3PE)2Au]+[AuX
4]−. These correspond to the addition of one halogen atom per gold atom of the AuI precursor. Compound 1, bis(triisopropylphosphane sulfide)gold(I) tetrachloridoaurate(III), [Au(C9H21PS)2][AuCl4] or [(
i
Pr3PS)2Au][AuCl4], crystallizes in space group P21/n with Z = 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 2, bis(tert-butyldiisopropylphosphane sulfide)gold(I) tetrachloridoaurate(III), [Au(C10H23PS)2][AuCl4] or [(
t
Bu
i
Pr2PS)2Au][AuCl4], crystallizes in space group P
1 with Z = 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 3, bis(tri-tert-butylphosphane sulfide)gold(I) tetrachloridoaurate(III), [Au(C12H27PS)2][AuCl4] or [(
t
Bu3PS)2Au][AuCl4], crystallizes in space group P
1 with Z = 1; both gold atoms lie on inversion centres. Compound 4a, bis(tert-butyldiisopropylphosphane sulfide)gold(I) tetrabromidoaurate(III), [Au(C10H23PS)2][AuBr4] or [(
t
Bu
i
Pr2PS)2Au][AuBr4], crystallizes in space group P21/c with Z = 4; the cation lies on a general position, whereas the gold(III) atoms of the two anions lie on inversion centres. Compound 4b, bis(tert-butyldiisopropylphosphane selenide)gold(I) tetrabromidoaurate(III), [Au(C10H23PSe)2][AuBr4] or [(
t
Bu
i
Pr2PSe)2Au][AuBr4], is isotypic with 4a. Compound 5a, bis(tri-tert-butylphosphane sulfide)gold(I) tetrabromidoaurate(III), [Au(C12H27PS)2][AuBr4] or [(
t
Bu3PS)2Au][AuBr4], is isotypic with compound 4a. Compound 5a, bis(tri-tert-butylphosphane sulfide)gold(I) tetrabromidoaurate(III), [Au(C12H27PS)2][AuBr4] or [(
t
Bu3PS)2Au][AuBr4], crystallizes in space group P
1 with Z = 1; both gold atoms lie on inversion centres. Compound 5b, bis(tri-tert-butylphosphane selenide)gold(I) tetrabromidoaurate(III), [Au(C12H27PSe)2][AuBr4] or [(
t
Bu3PSe)2Au][AuBr4], is isotypic with 5a. All AuI atoms are linearly coordinated and all AuIII atoms exhibit a square-planar coordination environment. The ligands at the AuI atoms are antiperiplanar to each other across the S...S vectors. There are several short intramolecular H...Au and H...E 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 1 involves two short C—Hmethine...Cl contacts (and some slightly longer contacts). For 2, four C—Hmethine...Cl interactions combine to produce zigzag chains of residues parallel to the c axis. Additionally, an S...Cl contact is observed that might qualify as a ‘chalcogen bond’. The packing of 3 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 4a/b and 5a/b, loose associations of the anions form part of the packing patterns. For all four compounds, these combine with an E...Br contact to form layers parallel to the ab plane.