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Intriguing Gold TrifluorideMolecular Structure of Monomers and Dimers:  An Electron Diffraction and Quantum Chemical Study

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journal contribution
posted on 18.03.2000, 00:00 authored by Balázs Réffy, Mária Kolonits, Axel Schulz, Thomas M. Klapötke, Magdolna Hargittai
The molecular geometry of monomeric and dimeric gold trifluoride, AuF3 and Au2F6, 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 AuF3 has C2v 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 D3h symmetry structure, 3A, to lie about 42 kcal/mol above the 1A1 symmetry ground state and the D3h symmetry singlet, 1A‘, 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 D2h symmetry planar, halogen-bridged geometry, with the gold atom having an approximately square-planar coordination, typical for d8 transition metals. The geometries of AuF and Au2F2 have also been calculated. The very short Au···Au separation in Au2F2 is indicative of the so-called aurophilic interaction. This effect is much less pronounced in Au2F6.

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