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

an hydrous H F or SO, at room temperature give adducts of composition M F2-2SbF,. 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*2SbF, has shown that the crystals are triclinic, space group P i , with unit-cell dimensions a = 5.224(1 ), b = 5.467(2), c = 8.779(2) A, a = 75.78(2), p = 89.02(2), y = 65.29(2)", and Z = 1. The Ag2+ ion has square-planar co-ordination with two Ag-F distances, 2.095(5) and 2.1 32(4) 8. Two further F atoms at 2.431 (3) A complete a distorted octahedron.Distorted [SbF,] -octahedra in the structure have four Sb-F distances between 1.830(4) and 1.875(3) A while two others are 1.942(4) and 1.965(4) A.Early vibrational spectroscopic work and ' 9Sn Mossbauer studies suggested the presence of [(SnF),]"' cations in the structures of the 1 : 1 adducts, SnF,-BF,, SnF,*AsF,, and SnF,.SbF,.' The overall accuracy of this interpretation has since been confirmed by a single-crystal X-ray determination on the arsenic compound which showed that it contains the cyclic cation [(SnF)3]3+.2 Another metal(r1) fluoro-cationic species is [Sn2F3]+, found in the SnF,-BF, system,, in 2SnF2-AsF, and 2SnF,-SbF,,4 and in Sn,ClF,.' The possibility that a wide range of cationic and pseudo-cationic species occur in metal difluoride systems is further evidenced by our own vibrational spectroscopic work which has suggested the presence of [MF]', [M2F3]f,6,7 or [(MF),]"+ and our crystallographic work which has confirmed the presence of [(AgF),]"+ in the AgF,*AsF, compound.'In the present paper we report the results of part of a programme designed to probe to what extent such cations appear in the MF2-SbF, system. Results and DiscussionThe adducts MF2*2SbF, (M = Mg, Ni, Zn, Fe, Co, Cu, Cr, Ag, Cd, or Pb) were prepared by the reaction of the appropriate metal difluoride with excess of SbF, at room temperature in anhydrous H F as solvent. All were soluble in H F but were obtained as crystalline solids after removal of volatiles under dynamic vacuum to constant weight (Scheme). MF2 + nSbF5 2 MF2*2SbF5(s0lv.) + ( n -2)SbF,(solv.) -% MF2=2SbF,(cryst.) Scheme. (i) Anhydrous HF solvent at room temperature. (ii) Pump at room temperature t Silver bis(hexafluoroantimonate).

Hexafluoro antimonates(V) of divalent metals, synthesis and properties

“…The X-ray diffraction study had revealed a true Ag2+ ion in a distorted octahedral environment (14). However, the course of the solvolysis and the final product are surprising.…”

“…Both Ni(SbF6)2 (11,12,14) and Sn(SbF6), (13) Alternate routes to P-Ag(SbF6)2: (a) 0.323 g of AgSbF6 is allowed to react with an excess of S2O6F2 at room temperature. The white color of AgSbF6 changes immediately to black-brown. '…”

“…In AgF2.2SbF5, however, a true appears to be present and the crystal structure supports formulation as Ag(sbF6)~ (14).…”

“…When moving from ionic SbF6-to coordinated SbF6-in these compounds, vibrational spectra become more complex and are less readily interpreted. As a consequence, in a recent publication, formulation as MF2.2SbF5 is employed for materials obtained in this manner (14).…”

Structure of the 1:1 silver(II) fluoride–arsenic(V) fluoride adduct, AgF2.AsF5

“…The AsF 6 ions are close to octahedral; the single non-bridging F(3) atom is closer 11.677 (7) A] than the remainder, which span the range 1.714 (4)-1.729 (6) A. The structure of AgFE.ASF 5 is very different from that of AgF 2 itself (Fischer, Schwarzenbach & Rietveld, 1971) and from that of AgFE.2SbF 5 (Gantar, Leban, Holloway & Frlec, 1987), in both of which the coordination around the Ag atom is probably best regarded as square planar. The average bond length of the Ag-F bonds in the square plane about Ag in AgF2.2SbF 5 [2.114 (5) A] is a little longer than the equivalent in AgF 2 [2.071 (6)AI.…”