The crystal structure of germanium difluoride

Abstract

Crystals of germanium difluoride are orthorhombic, a= 4·682, b= 5·178, c= 8·312 Å, Z= 4, space group P2₁2₁2₁. The structure was determined from the three-dimensional Patterson function, and refined by least-squares, the final R being 0·129 for 225 reflexions.

The fluoride is a strong fluorine-bridged chain polymer, in which the parallel chains are cross-linked by weak fluorine bridges. The structural unit of the strongly bridged chains is a trigonal pyramid of three fluorine atoms and an apical germanium atom, with Ge–F distances of 1·79, 1·91, and 2·09 Å and F–Ge–F angles of 85·0, 85·6, and 91·6°. The two longer-bonded fluorine atoms are structurally equivalent and join each germanium atom to its two neighbours in the chain. The fluorine atom 1·79 Å distant from each germanium atom makes a weak bridge bond with a germanium atom in an adjacent chain, 2·57 Å distant. This longest-bonded fluorine atom is almost opposite the fluorine atom at 2·09 Å, the F–Ge–F angle being 163°. The poor fluorine atom packing and the geometry of the [GeF₄] group are consistent with steric activity of the non-bonding valence electron pair. The [GeF₄] group may be described as a distorted trigonal bipyramidal arrangement of four fluorine ligands and an (equatorial) electron pair, about a germanium atom.