- The first example of a mixed valence ternary compound of silver with random distribution of Ag(i) and Ag(ii) cations
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The reaction between colourless AgSbF6 and sky-blue Ag(SbF6)2 (molar ratio 2:1) in gaseous HF at 323 K yields green Ag3(SbF6)4, a new mixed-valence ternary fluoride of silver. Unlike in all other Ag(i)/Ag(ii) systems known to date, the Ag+ and Ag2+ cations are randomly distributed on a single 12b Wyckoff position at the 4ˉ axis of the I4ˉ3d cell. Each silver forms four short (4 × 2.316(7) ?) and four long (4 × 2.764(6) ?) contacts with the neighbouring fluorine atoms. The valence bond sum analysis suggests that such coordination would correspond to a severely overbonded Ag(i) and strongly underbonded Ag(ii). Thorough inspection of thermal ellipsoids of the fluorine atoms closest to Ag centres reveals their unusual shape, indicating that silver atoms must in fact have different local coordination spheres; this is not immediately apparent from the crystal structure due to static disorder of fluorine atoms. The Ag K-edge XANES analysis confirmed that the average oxidation state of silver is indeed close to +1 1/3. The optical absorption spectra lack features typical of a metal thus pointing out to the semiconducting nature of Ag3(SbF6)4. Ag3(SbF6)4 is magnetically diluted and paramagnetic (μeff = 1.9 μB) down to 20 K with a very weak temperature independent paramagnetism. Below 20 K weak antiferromagnetism is observed (Θ = -4.1 K). Replacement of Ag(i) with potassium gives K(i)2Ag(ii)(SbF6)4 which is isostructural to Ag(i)2Ag(ii)(SbF6)4. Ag3(SbF6)4 is a genuine mixed-valence Ag(i)/Ag(ii) compound, i.e. Robin and Day Class I system (localized valences), despite Ag(i) and Ag(ii) adopting the same crystallographic position.
- Mazej, Zoran,Micha?owski, Tomasz,Goreshnik, Evgeny A.,Jagli?i?, Zvonko,Ar?on, Iztok,Szyd?owska, Jadwiga,Grochala, Wojciech
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- The volume-based thermodynamics (VBT) and attempted preparation of an isomeric salt, nitryl chlorate: [NO2][ClO3]
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Nitrosyl perchlorate, [NO][ClO4], is a known and stable salt. In this contribution we describe the attempt to synthesize the isomeric compound nitryl chlorate, [NO2][ClO3]. The results are discussed on the basis of volume-based thermodynamics (VBT).
- Bhasin, Kuldip K.,Crawford, Margaret-Jane,Jenkins, H. Donald Brooke,Klapoetke, Thomas M.,Liebman, Joel F.
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p. 897 - 900
(2008/10/09)
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- Silver(I) Undecafluorodiantimonate(V)
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The reaction between AgBF4 and excess of SbF5 in anhydrous hydrogen fluoride (aHF) yields the white solid AgSb2F 11 after the solvent and the excess of SbF5 have been pumped off. Reaction between equimolar amounts of AgSb2F 11 and AgBF4 yields AgSbF6. Meanwhile, oxidation of solvolyzed AgSb2F11 in aHF by elemental fluorine yields a clear blue solution of solvated Ag(II) cations and SbF 6- anions. AgSb2F11 is orthorhombic, at 250 K, Pbca, with a = 1091.80(7) pm, b = 1246.28(8) pm, c = 3880.2(3) pm, V = 5.2797(6) nm3, and Z = 24. The crystal structure of AgSb2F 11 is related to the already known crystal structure of H 3OSb2F11. Vibrational spectra of AgSb 2F11 entirely match the literature-reported vibrational spectra of β-Ag(SbF6)2, for which a formulation of a mixed-valence Ag(I)/Ag(III) compound was suggested (AgIAg III(SbF6)4). On the basis of obtained results it can be concluded that previously reported β-Ag(SbF6) 2 is in fact Ag(I) compound with composition AgSb2F 11.
- Mazej, Zoran,Benkic, Primoz
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p. 8337 - 8343
(2008/10/09)
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- Multinuclear NMR solution studies on complexes of hexakis(pyrazol-1-yl)benzene (hpzb) with Ag(I)
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The reaction of the polydentate N-donor ligand hexakis(pyrazol-1-yl)benzene (hpzb) with AgSbF6/PPh3 or AgClO4PPh3 in a 1:1 ratio leads to the complexes [Ag(PPh3)(hpzb)]SbF6 (1) or [Ag(PPh3)(hpzb)]ClO4 (3). When two or three equivalents of the silver derivatives are used the species [Ag(PPh3)2]X are formed in addition to 1 or 3. In the case of SbF6- the remaining Ag+ competes with AgPPh3+ for coordination to hpzb and the derivative [Ag(hpzb)]SbF6 (2) is also obtained, while in the case of ClO4- the insoluble salt AgClO4 is formed. The same reactions performed with hpzb-15N12 confirmed the presence of the N-donor ligand in 1-3. At room temperature a Ag-P dissociation process is observed for all the derivatives containing Ag-PPh3 fragments. Complexes 1-3 show in solution an intramolecular argentotropic shift that makes the six pyrazolyl rings of the hpzb ligand equivalent on the 1H NMR time scale. When the amount of counteranion present in solution is sufficiently high, an intermediate of lower coordination number (stabilized with the anion) is observed for complexes 1 and 3 in the low temperature 31P NMR spectra in addition to the three-coordinated species. This intermediate is more stable in the case of ClO4- due to the higher coordinating ability of this anion.
- Caballero, Agustín,Guerrero, Ana,Jalón, Félix A.,Manzano, Blanca R.,Claramunt, Rosa M.,Santa María, M. Dolores,Escolástico, Consuelo,Elguero, José
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p. 168 - 174
(2008/10/08)
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- Reaction of azides with dioxygenyl salts: Is dioxygenyl azide existent?
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The reactivity of sodium azide, activated sodium azide and hydrazinium azide towards various dioxygenyl tetrafluoroborate and dioxygenyl hexafluoroantimonate salts was studied both at low temperature in SO2 solution and in the solid state. Under no circumstances the formation of dioxygenyl azide, O2N3, could be observed. This is in agreement with high level quantumchemical ab initio computations at correlated level (MP2, PMP2, CISD), predicting the decomposition of hypothetical O2+(g) / N3-(g) to be thermodynamically highly favourable (MP2: -326; PMP2: -328; CISD: -369 kcal mol-1). Moreover, no true minimum for covalently bound dioxygenyl azide was found at any level of theory applied. The combustion of O2BF4 with either N2H5N3 (spontaneous reaction on contact in a coaxial solid-propellant system) or NaN3 (safe to handle, highly exothermic reaction after ignition) is discussed in terms of high energetic materials. Gauthier-Villars.
- Holfter,Klapoetke,Schulz
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p. 855 - 864
(2008/10/08)
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- Preparation and structural and magnetic properties of AgF+MF6- (M = Ir, Ru, Sb, Bi) and Ag2+(BiF6-)2
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AgFMF6 salts (M = Ir, Ru, Sb, Bi) have been prepared by the action of elemental F2 in AHF on AgMF6, and for AgFBiF6, also by interaction of Ag(BiF6)2 with KBF4 or KPF6 in AHF. Three structure types have been identified. AgFIrF6 {orthorhombic Pnma, a = 7.628(2) ?, b = 7.067(2) ?, c = 10.253(4) ?, V = 552.7(3) ?3, and Z = 4, with R = 0.026 and Rw = 0.030 for 531 observed reflections and 50 parameters refined by full-matrix least squares, Mo Kα radiation at 298 K} is isostructural with AgFAsF6 and AgFAuF6, the one dimensional cation (Ag-F)nn+, showing Ag(II) linearly coordinated to two F ligands with Ag-F = 1.977(9) and 2.014(9) ? and Ag-F-Ag = 146.0(5)°. In AgFRuF6 {monoclinic P21/n, a = 8.3432(13) ?, b = 5.4933(8) ?, c = 11.9286(22) ?, β = 108.36(1)°, V = 518.9(3) ?3, and Z = 4, with R = 0.027 and Rw = 0.028 for 1511 observed reflections and 83 parameters refined by full matrix least squares, Mo Kα radiation at 298 K} the Ag(II) is nearly square coordinated by four F; two cis F, each shared nearly equally with another Ag(II) {Ag-F = 2.007(3) and 2.018(2) A, Ag-F-Ag = 155.9(2)°} give the cation a ribbonlike polymeric character. The other two F ligands of the square array {Ag-F = 2.140(3) and 2.158(3) ?} are each associated with a different RuF6-, each of which is so linked to two Ag(II) moieties. AgFMF6 (M = Sb, Bi) belong to a third structure type. The cation chains of the AgF+MF6- salts have approximate temperature independence of magnetic susceptibility, akin to that of metallic systems. In contrast, Ag(BiF6)2 {triclinic P1, a = 5.218(2) ?, b = 5.579(1) ?, c = 8.934(2) ?, α = 76.08(2)°, β = 88.93(2)°, γ = 65.08(2)°, V = 228.0(1) ?3, and Z = 1, with R = 0.055 and Rw = 0.067 for 1327 observed reflections and 41 parameters refined by full-matrix least squares, Mo Kα radiation at 298 K}, which is isostructural with Ag(SbF6)2, shows approximate obedience to the Curie-Weiss law. AgRuF6BiF6 appears to be similar. In the structure of Ag(BiF6)2, each Ag(II) is linked in nearly square array to four F ligands of four surrounding BiF6- ions {Ag-F = 2.096(9) ? × 2 and 2.122(9) ? × 2}, two other anions making contact normal to that plane, with Ag-F = 2.440(10) ?.
- Lucier,Münzenberg,Casteel Jr.,Bartlett
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p. 2692 - 2698
(2008/10/08)
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