Metal(<scp>II</scp>) 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.