ISSN:
0044-2313
Keywords:
Mixed-valent oxide of cobalt
;
structure
;
MAPLE, CHARDI, MEFIR-FIT
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
A New Mixed-Valent Oxide of Cobalt(I, II): Rb5Co2O4For the first time we obtained a new mixed-valent oxide of mono- and divalent Cobalt. Black-red single-crystals of Rb5Co2O4 were prepared by heating powders of “Rb6CdO4” in closed Co-cylinders at 500° during 48 days.Structure solution and refinement are covered by two measurements with four-circle diffractometers. MoKα: 2 145 Io(hkl), out of 2 818 Io(hkl), R = 9.85%, Rw = 5.93% AgKα: 1 813 Io(hkl) out of 4 007 Io(hkl), R = 9.46%, Rw = 6.51%) and confirm the space-group P1. The lattice constants are a = 696.4(1) pm, b = 922.2(3) pm, c = 958.9(3) pm, α = 117.99(2)°, β = 89.96(2)°, γ h= 108.12(2)°, Z = 2According to its composition Rb10[OCoO]2[OCoO2CoO] the structure is built up by two Co atoms of chemically and crystallographically different nature. We find isolated dumb-bell-like anions [O—Co—O]3- being already known with monovalent Co (e. g. K3CoO2) together with units [OCoO2CoO]4- of two connected triangles CoO3 being well-known from K2BeO2 ≜ K4[Be2O4]. ECoN/mEFIR calculations are made starting with values obtained by a new procedure called “MEFIR-FIT”.
Notes:
Durch 48tägiges Tempern von Rb6CdO4 in verschlossenen Co-Zylindern bei 500°C wurde erstmals ein gemischt-valentes Oxid des ein- und zweiwertigen Cobalts in Form von schwarzroten Einkristallen dargestellt. Die Strukturaufklärung mittels Vierkreisdiffraktometer (zwei Messungen: MoKα: 2 145 von 2 818 Io(hkl), R = 9,85%, Rw = 5,93% AgKα: 1 813 von 4 007 Io(hkl), R = 9,46%, Rw = 6,51%) belegt die Raumgruppe P1. Die Gitterkonstanten nach Pulverdaten sind a = 696,4(1) pm, b = 922,2(3) pm, c = 958,9(3) pm, α = 117,99(2)°, β = 89,96(2)°, γ = 108,12(2)°, Z = 2 (Standardabweichungen in Einheiten der letzten Stelle Klammern).Die chemisch unterschiedlichen Co-Teilchen nehmen auch kristallographisch unterschiedliche Umgebungen an: Während CoI in Form „isolierter“, linearer Hanteln [O—Co—O]3- vorliegt, bildet CoII[Co2O4]4--Einheiten in Form zweier kantenverknüpfter Dreiecke CoO3, analog dem Aufbau des Anions in K4[Be2O4] [2].Zur Berechnung der Startwerte der „Mittleren Fiktiven Ionenradien“ (MEFIR) wird ein neues Verfahren (MEFIR-FIT) angewandt.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19936190320
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