The crystal structure of gold trifluoride

Abstract

Crystals of gold trifluoride are hexagonal, a= 5·149, c= 16·26 Å, U= 373·3 ų, D_m= 6·72, Z= 6, D_c= 6·78, space-group P6₁22–D₆². The structure was determined from a Patterson projection, and refined by three-dimensional least squares, the final R being 0·090 for 193 reflections.

Gold trifluoride is a fluorine-bridged polymer, with gold atoms linked to square-planar arrangements of fluorine atoms. Each square-planar unit is linked to two adjacent units by cis fluorine bridges, giving an infinite hexagonal helix, with Au–F (bridging)= 2·04 Å, Au–F (non-bridging)= 1·91 Å, Au–F–Au = 116°. Weak cross-linking between chains, with Au⋯F = 2·69 Å, completes a tetragonally-elongated octahedral environment around each gold atom.

Gold trifluoride is the least densely packed of the noble-metal trifluorides. This and the geometry of the fluorine ligand co-ordination are consistent with the antibonding nature of one of the electron pairs of the low-spin d⁸ electron configuration of gold(III).