The Trichlorogermanite(II) Anion and its Gold(I) Complexes

Abstract

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 the 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]}2 2+ 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.