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

journal contribution

posted on 18.03.2000, 00:00 authored by Balázs Réffy, Mária Kolonits, Axel Schulz, Thomas M. Klapötke, Magdolna HargittaiThe 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*_{2}*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*_{v}*D*_{3}*symmetry structure,*_{h}^{3}*A**‘*, to lie about 42 kcal/mol above the^{1}*A*_{1}symmetry ground state and the*D*_{3}*symmetry singlet,*_{h}^{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*_{2}*symmetry planar, halogen-bridged geometry, with the gold atom having an approximately square-planar coordination, typical for d*_{h}^{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}.