The trichlorogermanite(II) anion and its gold(I) complexes

Tetraphenylphosphonium trichlorogermanite(II) (1) has been prepared (as a reference compound) from Ph₄P⁺ Cl^- and GeCl₂(dioxane) in tetrahydronaphthalene. Its structure has been determined by single crystal X-ray methods. The lattice contains independent monomeric GeCl₃^- anions (Ge-Cl distances between 2.290 and 2.320 Å, Cl-Ge-Cl angles between 95.33 and 98.27°). Treatment of (Ph₃As)AuCl with GeCl₂(dioxane) affords (Ph₃As)AuGeCl₃ in high yields as a germylene insertion product (2). The complex is a dimer in ihe crystal with a short Au--Au contact of 2.9415(4) Å and bent As-Au-Ge axes [169.353(13)°]. The GeCl₃ ligand has shorter Ge-Cl bonds [2.175 to 2.183 Å] and wider Cl-Ge-Cl angles than in the free anion [100.9 to 101.9°]. The analogous reaction with CH₂(AsPh₂AuCl)₂ leads only to a mono-insertion product in the form of a salt with {[CH₂(AsPh₂)₂Au]}₂²⁺ dications and two [ClAuGeCl₃]^- anions (3). In the lattice these three ions form a centrosymmetrical tetranuclear unit through short Au--Au contacts. The resulting z-shaped Au--Au--Au--Au chain has distances of 3.0499(6) (twice) and 3.1613(8) Å and angles of 118.833(8)° (twice). The geometry of the GeCl₃ units is similar to that in 2. {(Et₃N)Au[P(o-Tol)₃]}⁺ PF₆^- (4) was obtained as a by-product in several reactions with the bulky phosphine and where NEt₃ was used as a base. The crystals contain two crystallographically independent cations with a similar core structure, but different conformations of the substituents. Both the P-Au and the N-Au bonds are elongated owing to steric effects.