10026-12-7Relevant articles and documents
Reactivity of transition metal fluorides. III. Higher fluorides of vanadium, niobium, and tantalum
Canterford,O'Donnell
, p. 1442 - 1446 (1966)
A series of oxidation-reduction and halogen-exchange reactions has been used to compare the chemical reactivities of the pentafluorides of vanadium, niobium, and tantalum. Vanadium pentafluoride is extremely reactive and its reaction pattern with many reagents is extremely complex, depending largely on relative proportions of reagents and other experimental conditions. The pentafluorides of niobium and tantalum are very much less reactive than that of vanadium and are similar to each other. There is some evidence that of the two, the niobium compound is slightly more reactive. The reactivities of these three pentafluorides are discussed in terms of their physical properties and in relation to the higher fluorides of neighboring transition elements.
Austin, T. E.,Tyree, S. Y.
, p. 141 - 142 (1960)
Electrochemical and spectroscopic studies of the chloro and oxochloro complex formation of Nb(V) and Ta(V) in NaCl-AlCl3 melts
Von Barner,Bjerrum
, p. 9847 - 9851 (2005)
The equilibrium constant for the chloro complex formation of Nb(V) NbCl6-?NbCl5+Cl- (i) in NaCl-AlCl3 melts at 175°C was found to be pKi = 2.86(5). The oxochloro complex formation of Nb(V) and Ta(V) in NaCl-AlCl 3 melts at 175°C could be explained by the following equilibria: MOCl4-?MOCl3+Cl- (ii) MOCl 3?MOCl2++Cl- (iii) where M = Nb and Ta. The equilibrium constants determined by potentiometric measurements with chlorine-chloride electrodes were, for M = Nb, pKii, = 2.21(4) and pKiii = 3.95(5) and, for M = Ta, pKii = 2.743(15) and pKiii = 4.521(13). NbCl6- has two bands in the UV-vis region, a strong one at 34.7 × 103 cm-1 and a weaker one at 41.6 × 103 cm-1. The MOCl 4- complexes showed in the case of Nb(V) absorption bands at 32.7 and 42.9 × 103 cm-1 and in the case of Ta(V) at 38.6 and 48.1 × 103 cm-1.
Delafontaine, M.,Linebarger, C. E.
, p. 532 - 536 (1896)
Preparations, Properties, and Crystal and Molecular Structures of the Cyanomethane Adducts of Niobium(IV) Chloride and Di-μ-sulphido-bis
Benton, A. John,Drew, Michael G. B.,Hobson, Richard J.,Rice, David A.
, p. 1304 - 1309 (1981)
The cyanomethane adduct of NbCl4 analyses for NbCl4*3CH3CN (1).A crystal-structure determination of this species shows that it contains cis octahedral and a solvent CH3CN molecule.The unique bond lengths are Nb-N 2.220(13) Angstroem and Nb-Cl 2.328(2),2.343(6), and 2.349(4) Angstroem.The crystals of (1) are orthorhombic with unit-cell dimensions a=10.437(11), b=13.883(12), c=9.828(9) Angstroem, Z=4, and space group Pnma.A total of 729 reflections above background have been collected on a diffractometer and refined to R 0.051.When the cyanomethane adducts of NbX4 (X=Cl or Br) are treated with Sb2S3 in cyanomethane, adducts of NbX2S (X=Cl or Br) are formed.The products contain 2> in which there is a ring.The crystal structures of two compounds, (2) and (3), containing the 2> dimeric unit have been determined.In (2) there are two molecules of occluded CH3CN for each dimer while (3) has one.Both (2) and (3) are triclinic with space group P, with (2) having a=9.031(7), b=9.367(6), c=8.360(8) Angstroem, α=108.72(9), β=94.93(7), γ=105.70(8) degree, Z=1 and (3) having a=14.965(18), b=8.838(17), c=9.543(23) Angstroem, α=112.42(18), β=84.39(28), γ=103.65(21) degree, z=2.For (2), 1434, and for (3), 1530, independent reflections above background have been collected on a diffractometer and refined to R 0.056 and 0.050 respectively.The dimer configurations in (2) and (3) are identical.The niobium atoms are in a pseudo-octahedral enviroment consisting of two cis sulphur, two trans chlorine , and two cis nitrogen atoms .In addition, in each dimer there is a Nb-Nb single bond .
Chemistry of polynuclear metal halides. II. Preparation of polynuclear niobium chloride and bromide
Fleming, Peter B.,Mueller, Leta A.,McCarley, Robert E.
, p. 1 - 4 (1967)
Improved preparations leading to the compounds Nb6X14·8H2O (X = Cl, Br) are described. High yields of Nb6Cl122+ were obtained by the high-temperature reaction of KCl and Nb3Cl8 which proceeds via 14KCl + 5Nb3Cl8 = 2K4Nb6Cl18 + 3K2-NbCl6. Extraction of this reaction mixture with water provides a convenient route to Nb6Cl14·8H2O. The attempted formation of Nb6Cl14 via direct reduction of NbCl5 with aluminum was unsuccessful. However, aluminum reduction of NbBr5 provided an unidentified anhydrous product from which yields of up to 35% Nb6Br122+ were extracted. Equilibration reactions involving niobium and Nb3Br8 at temperatures up to 975° gave no evidence for phases having Br: Nb 6Cl122+ and Nb6Br122+ are given. Copyright 1967 by the American Chemical Society.
Balke, C. W.,Smith, E. F.
, p. 1637 - 1668 (1908)
Knox, K.,Tyree, S. Y.,Srivastava, R. D.,Norman, V.,Bassett, J. Y.,Holloway, J. H.
, p. 3358 - 3361 (1957)
MacCordick, J.,Kaufmann, G.,Rohmer, R.
, p. 3059 - 3070 (1969)
Hall, D.,Smith, E. F.
, p. 1369 - 1403 (1905)
Synthesis and crystal structure of U2Ta6O19, a new compound with Jahnberg-structure and a note to the first oxide chlorides in the systems Th/Nb/O/Cl and Th/Zr(Hf)/Nb/O/Cl
Schleifer, Michaela,Busch, Jochen,Albert, Barbara,Gruehn, Reginald
, p. 2299 - 2306 (2008/10/08)
Black crystals of U2Ta6O19 with hexagonal shape were obtained (at T1) by chemical transport using HCl (p (HCl, 298 K) = 1 atm; silica tube) as transport agent in a temperature gradient (T2 → T1; 1000 °C → 950 °C) and using a mixture of UO2, Ta2O5, and HfO2 (or ZrO2) (1:2:2) as starting materials (at T2). For the structure determination the best result was achieved in space group P63/mcm (No. 193, a = 6.26(2) A, c = 19.86(6) A). U2Ta6O19 is isotypical to Th2Ta6O19. In the crystal structure each uranium atom is surrounded by oxygen atoms like a bi-capped trigonal antiprism and tantalum atoms like a pentagonal bipyramid (CN = 7). Like the Jahnberg Structures both coordination polyhedra arrange themselves in separate layers (U-O-polyhedra, in o-, Ta-O-polyhedra in p-layers) so that in the direction of the c-axis the sequence of layers is p-p-o. Using chemical transport it was possible to prepare the compounds Th12Nb16O63Cl2 and Th8M4Nb16O63Cl2 (M = Zr, Hf), which are the first quaternary and quinquinary examples in these systems. They crystallize isotypically.
