91899-63-7Relevant articles and documents
Silver Trifluoride: Preparation, Crystal Structure, Some Properties, and Comparison with AUF3
?emva, Boris,Lutar, Karel,Jesih, Adolf,Casteel Jr., William J.,Wilkinson, Angus P.,Cox, David E.,Von Dreele, Robert B.,Borrmann, Horst,Bartlett, Neil
, p. 4192 - 4198 (1991)
Red, diamagnetic AgF3 is precipitated from anhydrous hydrogen fluoride (AHF) solutions of AgF4- salts by addition of fluoro acids (L) such as BF3, PF5, or AsF5: AgF4-+ L → AgF3 + LF-. With additional AsF5, silver(III) is reduced: AgF3 + AsFf → AgFAsF6 + 1/2F2. Such reduction does not occur with BF3, and the latter acid is therefore preferred for the preparation of stoichiometric AgF3. AgF3 is thermodynamically unstable and, in contact with AHF, at ～20 °C, loses F2 in less than 19 h according to the equation 3AgF3 → Ag3F8 + 1/2F2. The trifluoride is isostructural with AuF3. To provide for meaningful comparisons, the structure of AuF3 was redetermined. AgF3 and AuF3 were successfully refined in space group P61-D62 (No. 178) by using the Rietveld method from time-of-flight neutron powder diffraction data from 100-mg samples contained in 2-mm capillary tubes. The 7762 observations for AgF3 yielded a = 5.0782 (2) A?, c = 15.4524 (8) A?, and V= 345.10 (2) A?3, the reliability parameters for the structure being Rwp = 6.21 and Rp = 3.83%. From the 7646 observations for AuF3, a = 5.1508 (1) A?, c= 16.2637 (7) A?, V= 373.68 (2) A?33, and Rwp = 11.21 and Rp = 7.58%. The lilver or gold atom lies at the center of an elongated octahedron with two Ag-F(1) = 1.990 (3) A?, two Au-F(1) = 1.998 (2) A?, two Ag-F(2) = 1.863 (4) A?, and two Au-F(2) = 1.868 (3) A?, the approximately square, isodimensional AF4 units being joined by symmetrical μ-fluoro bridges (two F(1) in cis relationship in the AF4 unit) to form the 61 (or 65) helical chains where Ag-F(1)-Ag = 123.2 (2)° and Au-F(1)-Au = 119.3 (2)°. The ～5-A?3 smaller formula unit volume of AgF3 compared with AuF3 and the shorter z axis interatomic distance (Ag-F = 2.540 (4), Au-F = 2.756 (8) A?) are in accord with the tighter binding of the Ag(III) d-orbital electrons evident in the strong oxidizing properties of Ag(III). Interaction of AgF+ with AgF4- (1:1) in AHF yields maroon AgIIAgIIIF5. The latter interacts with AgF3 to yield AgIIAgIII2F8, which is identical with the product of the decomposition of AgF3 at 20 °C in AHF and with the material previously described1,2 AgF3. The magnetic susceptibility for AgIIAgIII2F8 obeys the Curie-Weiss law (4-280 K) with θ = -4.2 (5) ° and μeff = 1-924 (3) μB.
