Fluoride crystal structures. Part I. Tungsten oxide tetrafluoride

Abstract

Crystals of tungsten oxide tetrafluoride are monoclinic, space group C2/m, with a= 9·65, b= 14·42, c= 5·15 Å, and β= 95·4°. The structure is very similar to that of niobium and tantalum pentafluorides and was refined by three-dimensional least-squares methods, the final R being 0·128 for 488 independent reflections. The tetrameric molecular unit has tungsten atoms at the corners of a square, linked by nearly linear, bridging oxygen atoms, with fluorine atoms completing the octahedral co-ordination about each tungsten atom. The light atoms form a slightly distorted octahedron, with the tungsten atom displaced 0·3 Å from its centre, away from the bridging oxygen atoms. The i.r. spectra of the compound in the solid and vapour states are reported and discussed.