Intriguing Gold TrifluorideMolecular Structure of Monomers and Dimers:  An Electron Diffraction and Quantum Chemical Study

Abstract

The molecular geometry of monomeric and dimeric gold trifluoride, AuF 3 and Au 2 F 6 , has been determined by gas-phase electron diffraction and high-level quantum chemical calculations. Both experiment and computation indicate that the ground-state structure of AuF 3 has C 2V symmetry, rather than 3-fold symmetry, with one shorter and two longer Au-F bonds and an almost T-shaped form, due to a first-order Jahn-Teller effect. CASSCF calculations show the triplet D 3h symmetry structure, 3 A′, to lie about 42 kcal/mol above the 1 A 1 symmetry ground state and the D 3h symmetry singlet, 1 A′, even higher than the triplet state, by about a further 13 kcal/mol. The molecule has a typical "Mexican-hat"-type potential energy surface with three equal minimum-energy structures around the brim of the hat, separated by equal-height transition structures, about 3.6 kcal/mol above the minimum energy. The geometry of the transition structure has also been calculated. The dimer has a D 2h symmetry planar, halogen-bridged geometry, with the gold atom having an approximately square-planar coordination, typical for d 8 transition metals. The geometries of AuF and Au 2 F 2 have also been calculated. The very short Au‚‚‚Au separation in Au 2 F 2 is indicative of the so-called aurophilic interaction. This effect is much less pronounced in Au 2 F 6 .

The chemistry of gold-fluoro compounds: A continuing challenge for gold chemists

“…In comparison, AuCl3 exits as a chlorobridged dimer in the solid state ( Figure 1B) (14,36). The gasphase structures of AuX3 (X = F, Cl, Br and I) have recently been investigated using computational methods (14,37,38). These results show that AuX3 compounds are T-shaped (C2v) structures due to first-order Jahn-Teller distortion.…”

Investigation of Gold Fluorides and Noble Gas Complexes by Matrix‐Isolation Spectroscopy and Quantum‐Chemical Calculations

“…The most prominent oxidation state in gold chemistry is + III, as represented by AuF 3 and higher oligomers Au 2 F 6 and Au 3 F 9 , which have been extensively investigated experimentally [2][3][4][5] and theoretically. [6,7] Gas-phase electron diffraction (GED) experiments of the monomer have shown that this compound forms an almost T-shaped structure, owing to firstorder Jahn-Teller distortion, [2] whereas a helical structure was determined for its crystal.…”

“…[6,7] Gas-phase electron diffraction (GED) experiments of the monomer have shown that this compound forms an almost T-shaped structure, owing to firstorder Jahn-Teller distortion, [2] whereas a helical structure was determined for its crystal. [3,8] The planar dimer structure Au 2 F 6 with two bridging fluorine atoms was also studied in the gas phase.…”

Untersuchung von Goldfluoriden und ihren Edelgaskomplexen durch Matrixisolationsspektroskopie und quantenchemische Rechnungen

“…B. AuF 3 oder entsprechende hçhere Oligomere wie Au 2 F 6 oder Au 3 F 9 , die eingehend sowohl experimentell [2][3][4][5] als auch theoretisch [6,7] untersucht worden sind. GasphasenElektronenbeugungsexperimente (GED) des Monomers zeigten, dass dieses aufgrund eines Jahn-Teller-Effekts erster Ordnung [2] eine fast T-fçrmige Struktur bildet; im Kristall hingegen wurde eine helikale Struktur gefunden. [3,8] Die planare Dimerstruktur von Au 2 F 6 mit zwei verbrückenden Fluoratomen wurde ebenfalls in der Gasphase untersucht.…”

“…[3,8] Die planare Dimerstruktur von Au 2 F 6 mit zwei verbrückenden Fluoratomen wurde ebenfalls in der Gasphase untersucht. [2,6] Eine ähnliche Fluorverbrückung liegt bei der Dimerisierung und Trimerisierung von AuF 5 zu [Au 2 F 10 ] [9,10] oder [Au 3 F 15 ] [10,11] vor. Die im Vergleich zu den leichteren Homologen Silber und Kupfer ungewçhnlich hohe Oxidationsstufe + V ist auf das relativistische Maximum des Goldes zurück-zuführen.…”