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- Title
Homoleptic Gold Acetonitrile Complexes with Medium to Very Weakly Coordinating Counterions: Effect on Aurophilicity?
- Authors
Engesser, Tobias A.; Friedmann, Christian; Martens, Arthur; Kratzert, Daniel; Malinowski, Przemysław J.; Krossing, Ingo
- Abstract
A series of gold acetonitrile complexes [Au(NCMe)2]+[WCA]− with weakly coordinating counterions (WCAs) was synthesized by the reaction of elemental gold and nitrosyl salts [NO]+[WCA]− in acetonitrile ([WCA]− =[GaCl4]−, [B(CF3)4]−, [Al(ORF)4]−; RF =C(CF3)3). In the crystal structures, the [Au(NCMe)2]+ units appeared as monomers, dimers, or chains. A clear correlation between the aurophilicity and the coordinating ability of counterions was observed, with more strongly coordinating WCAs leading to stronger aurophilic contacts (distances, C−N stretching frequencies of [Au(NCMe)2]+ units). An attempt to prepare [Au(L)2]+ units, even with less weakly basic solvents like CH2Cl2, led to decomposition of the [Al(ORF)4]− anion and formation of [NO(CH2Cl2)2]+[F(Al(ORF)3)2]−. All nitrosyl reagents [NO]+[WCA]− were generated according to an optimized procedure and were thoroughly characterized by Raman and NMR spectroscopy. Moreover, the to date unknown species [NO]+[B(CF3)3CN]− was prepared. Its reaction with gold unexpectedly produced [Au(NCMe)2]+[Au(NCB(CF3)3)2]−, in which the cyanoborate counterion acts as an anionic ligand itself. Interestingly, the auroborate anion [Au(NCB(CF3)3)2]− behaves as a weakly coordinating counterion, which becomes evident from the crystallographic data and the vibrational spectral characteristics of the [Au(NCMe)2]+ cation in this complex. Ligand exchange in the only room temperature stable salt of this series, [Au(NCMe)2]+[Al(ORF)4]−, is facile and, for example, [Au(PPh3)(NCMe)]+[Al(ORF)4]− can be selectively generated. This reactivity opens the possibility to generate various [AuL1L2]+[Al(ORF)4]− salts through consecutive ligand-exchange reactions that offer access to a huge variety of AuI complexes for gold catalysis.
- Subjects
ANIONS; HOMOLEPTIC compounds; NITROSYL chloride; ACETONITRILE; SALTS
- Publication
Chemistry - A European Journal, 2016, Vol 22, Issue 42, p15085
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201602797