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 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, 3A', to lie about 42 kcal/mol above the 1A1 symmetry ground state and the D(3h) 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 D(2h) 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.
ASJC Scopus subject areas
- Colloid and Surface Chemistry