Die Pyridinaddukte der Goldhalogenide. 1. Darstellung und Struktur von [Hpy][AuCl4], AuCl3 · py, [AuCl2(py)2]Cl · H2O und [AuCl2(py)2][AuCl2]

Pyridine Adducts of the Gold Halides. 1. Synthesis and Structure of [Hpy][AuCl₄], AuC1₃ · py, [AuCl₂(py)₂]Cl · H₂O, and [AuCl₂(py)₂] [AuCl₂] HAuCl₄ reacts with pyridine in aqueous solution to form sparingly soluble [Hpy] [AuCl₄]. This goes into solution as [AuCl₂(py)₂]⁺ on adding an excess of pyridine. [Hpy][AuCl₄] decomposes above 195°C to HCl and AuCl₃ · py, which can also be obtained from NaAuCl₄ and pyridine. AuCl₂ · py is formed by the reaction of AuCl₂ · S(CH₂C₆H₄)₂ with pyridine in CHCl₃. According to the vibrational spectrum the complex is built up of trans[AuCl₂(py)₂]⁺ cations and [AuCl₂]^? anions. The IR spectra of [Hpy][AuCl₄], AuCl₃ · py, and [AuCl₂(py)₂]Cl · H₂O are discussed and assigned with respect to the crystal structures. [Hpy][AuCl₄] crystallizes monoclinic in the space group C2/m. In its structure alternating layers of [Hpy]⁺ cations and [AuCl₄]^? anions are observed. The monoclinic AuCl₃ · py (space group C2/c) consists of molecular complexes, wherein the gold atom is surrounded by three Cl atoms and one pyridine molecule in a square planar arrangement. The coordination is completed to an elongated octahedron by two more distant Cl atoms of neighbouring complexes. [AuCl₂(py)₂]Cl · H₂O crystallizes in the monoclinic space group P2₁/n. It forms planar trans[AuCl₂(py)₂]⁺ cations, weakly coordinated with an additional Cl^? ion and one H₂O molecule. The Au? Cl bond lengths in the complexes under investigation are in the range of 227 to 229 pm, the Au? N distances are between 197 and 199 pm.