Metal(II) hexafluoroantimonates: preparation and characterization of MF2·2SbF5(M = Mg, Ni, Zn, Fe, Co, Cu, Cr, Ag, Cd, or Pb) and the X-ray structure determination of AgF2·2SbF5

Abstract

Reactions of MF₂(M = Mg, Ni, Zn, Fe, Co, Cu, Cr, Ag, Cd, or Pb) with excess of SbF₅ in anhydrous HF or SO₂ at room temperature give adducts of composition MF₂·2SbF₅. Efforts to prepare similar adducts of the difluorides of Ca, Sr, and Ba led only to non-stoicheiometric compounds. Vibrational spectra and X-ray powder diffraction studies indicate that the Mg, Ni, and Zn compounds and the Fe, Co, and Cu compounds form two distinct isostructural triads. The remaining adducts have structures which differ from each other and from those of the two triads. A single-crystal X-ray study on AgF₂·2SbF₅ has shown that the crystals are triclinic, space group P, with unit-cell dimensions a= 5.224(1), b= 5.467(2), c= 8.779(2)Å, α= 75.78(2), β= 89.02(2), γ= 65.29(2)°, and Z= 1. The Ag²⁺ ion has square-planar co-ordination with two Ag–F distances, 2.095(5) and 2.132(4)Å. Two further F atoms at 2.431(3)Å complete a distorted octahedron. Distorted [SbF₆]^– octahedra in the structure have four Sb–F distances between 1.830(4) and 1.875(3)Å while two others are 1.942(4) and 1.965(4)Å.