Synthesis and characterization of perhalophenyltin derivatives. Study of their reactivity toward phosphine gold(I) chlorides

The (perhalophenyl)tin derivatives [SnR₄] (1-3) and [SnR₃Cl] (4-6) (R = C₆F₅, C₆F₃Cl₂, C₆Cl₅) were prepared from SnCl₄ and LiR or [SnR₄] in the appropriate molar ratio, while the dinuclear complexes [SnR₃]₂ (7-9) were obtained by treatment of [SnR₃Cl] with potassium under toluene reflux. Complexes 2, 6·0.5toluene and 7 were structurally characterized, the latter displaying a Sn-Sn bond of 2.808(7) Å, which indicates a strong tin-tin bond with covalent character in solid state. The hexaaryldistannanes 7-9 undergo transmetallation reactions with gold(I) derivatives, such as [AuCl(PPh₃)] or [(AuCl)₂(μ-dppm)], affording the neutral species [AuR(PPh₃)] (10-12) or [(AuR)₂(μ-dppm)] (13-15) or the ionic product [Au₃Cl₂(μ-dppm)₂][Sn(C₆F₅)₃Cl₂] (16). The crystal structures of 14·CH₂Cl₂, 15 and 16·2CH₂Cl₂ were determined by X-ray diffraction, the latter showing a Au₃ nearly equilateral triangular core in the cation with gold-gold contacts of 3.128(7) and 3.227(12) Å. The main difference between the molecular structures of 14·CH₂Cl₂ and 15 (both of them displaying intramolecular gold-gold contacts of 3.142(6) and 3.160(4) Å, respectively) is the presence of an intermolecular Au?Au interaction of 3.2126(8) Å in the case of the C₆F₃Cl₂ complex that gives rise to a tetranuclear unit.