Gold(I) and Gold(III) Trifluoromethyl Derivatives. Issue 43 (11th September 2013)

• Record Type: Journal Article
• Authors: Martínez‐Salvador, Sonia; Falvello, Larry R.; Martín, Antonio; Menjón, Babil
• Is Part Of: Chemistry. Volume 19:Issue 43(2013)
• Page Start: 14540
• Page End: 14552
• Publication Date: 2013-09-11
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201302142
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Trifluoromethylation of AuCl<sub>3</sub> by using the Me<sub>3</sub>SiCF<sub>3</sub>/CsF system in THF and in the presence of [PPh<sub>4</sub>]Br proceeds with partial reduction, yielding a mixture of [PPh<sub>4</sub>][Au<sup>I</sup>(CF<sub>3</sub>)<sub>2</sub>] (<bold>1′</bold>) and [PPh<sub>4</sub>][Au<sup>III</sup>(CF<sub>3</sub>)<sub>4</sub>] (<bold>2′</bold>) that can be adequately separated. An efficient method for the high‐yield synthesis of <bold>1′</bold> is also described. The molecular geometries of the homoleptic anions [Au<sup>I</sup>(CF<sub>3</sub>)<sub>2</sub>]<sup>−</sup> and [Au<sup>III</sup>(CF<sub>3</sub>)<sub>4</sub>]<sup>−</sup> in their salts <bold>1′</bold> and [NBu<sub>4</sub>][Au<sup>III</sup>(CF<sub>3</sub>)<sub>4</sub>] (<bold>2</bold>) have been established by X‐ray diffraction methods. Compound <bold>1′</bold> oxidatively adds halogens, X<sub>2</sub>, furnishing [PPh<sub>4</sub>][Au<sup>III</sup>(CF<sub>3</sub>)<sub>2</sub>X<sub>2</sub>] (X=Cl (<bold>3</bold>), Br (<bold>4</bold>), I (<bold>5</bold>)), which are assigned a <italic>trans</italic> stereochemistry. Attempts to activate CF bonds in the gold(III) derivative <bold>2′</bold> by reaction with Lewis acids under different conditions either failed or only gave complex mixtures. On the other hand, treatment of the gold(I) derivative <bold>1′</bold> with BF<sub>3</sub>⋅OEt<sub>2</sub> under mild conditions cleanly afforded the carbonyl derivative [Au<sup>I</sup>(CF<sub>3</sub>)(CO)] (<bold>6</bold>), which can be isolated as an extremely moisture‐sensitive light yellow crystalline solid. In the solid state, each linear F<sub>3</sub>C‐Au‐CO molecule weakly interacts with three symmetry‐related neighbors yielding an extended 3D network of aurophilic interactions (Au⋅⋅⋅Au=345.9(1) pm). The high <tex-math notation="tex"><![CDATA[$\tilde \nu $]]></tex-math><inline-graphic xlink:href="ark:/27927/pgg4t3tq4z4" mimetype="image" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><sub>CO</sub> value (2194 cm<sup>−1</sup> in the solid state and 2180 cm<sup>−1</sup> in CH<sub>2</sub>Cl<sub>2</sub> solution) denotes that CO is acting as a mainly σ‐donor ligand and confirms the role of the CF<sub>3</sub> group as an electron‐withdrawing ligand in organometallic chemistry. Compound <bold>6</bold> can be considered as a convenient synthon of the "Au<sup>I</sup>(CF<sub>3</sub>)" fragment, as it reacts with a number of neutral ligands L, giving rise to the corresponding [Au<sup>I</sup>(CF<sub>3</sub>)(L)] compounds (L=CN<italic>t</italic>Bu (<bold>7</bold>), NCMe (<bold>8</bold>), py (<bold>9</bold>), tht (<bold>10</bold>)).</p> </abstract>