Ce4Ag3Ge4O(0.5)--chains of oxygen-centered [OCe2Ce(2/2)] tetrahedra embedded in a [CeAg3Ge4] intermetallic matrix.
The oxidation of an intermetallic phase under high-pressure/high-temperature conditions led to the synthesis of Ce4Ag3Ge4O(0.5) exhibiting [OCe2Ce(2/2] tetrahedral chains, in which the oxygen atoms statistically occupy the tetrahedral centres. Starting from a 1:1:1 CeAgGe precursor (NdPtSb type), a multianvil high-pressure/high-temperature experiment at 11.5 GPa and 1250-1300 °C revealed Ce4Ag3Ge4O(0.5), crystallizing in the space group Pnma with the following lattice parameters: a = 2087.3(4), b = 439.9(1), and c = 1113.8(2) pm. Magnetic measurements showed Curie-Weiss behavior above 100 K with an experimental magnetic moment of 2.42 µB per Ce atom, close to the value for the free Ce(3+) ion, clearly indicating trivalent cerium in Ce4Ag3Ge4O(0.5). Full potential GGA+U band structure calculations resulted in metallic properties and a magnetic ground state with one unpaired 4f-electron per cerium in agreement with the experiments.
The quaternary arsenide oxides Ce9Au5–xAs8O6 and Pr9Au5–xAs8O6
Abstract The quaternary gold arsenide oxides Ce9Au5−xAs8O6 and Pr9Au5−xAs8O6 were synthesized from the rare earth elements (RE), rare earth oxides, arsenic and gold powder at maximum annealing temperatures of 1173 K. The structures were refined from single crystal X-ray diffractometer data: Pnnm, a=1321.64(6) pm, b=4073.0(3), c=423.96(2), wR2=0.0842, 3106 F2 values, 160 variables for Ce9Au4.91(4)As8O6 and Pnnm, a=1315.01(4), b=4052.87(8), c=420.68(1) pm, wR2=0.0865, 5313 F2 values, 160 variables for Pr9Au4.75(1)As8O6. They represent a new structure type and show a further extension of pnictide oxide crystal chemistry. A complex polyanionic gold arsenide network [Au5As8]15− (with some disorder in the gold substructure) is charge compensated with polycationic strands of condensed edge-sharing O@RE4/4 and O@RE4/3 tetrahedra ([RE4O3]212+) as well as RE3+ cations in cavities.
Die Koordinationszahl 5 bei wolframaten und molybdaten: Über K4[WO5], K4[MoO5] und Rb4[WO5]
Zusammenfassung Nach Einkristalldaten kristallisiert farbloses K 4 [WO 5 ] triklin ( P 1 ): a = 1692,18(15) pm; b = 1021,19(9) pm; c = 626,39(6) pm; α = 96,139(7)°; β = 92,611(8)°; γ = 94,239(7)°; Z = 6 (Vierkreisdiffraktometerdaten; Philips PW 1100; 5845 I o ( hkl ); Mo K \ ga-Strahlung; R = 5,7%). Nach Pulverdaten sind K 4 [MoO 5 ], mit a = 1690,25(18) pm, b = 1019,49(14) pm, c = 625,82(8)pm, α = 96,150(9)°, β = 92,634(9)° und γ = 94,223(10)°, und Rb 4 [WO 5 ], mit a = 1758,93(15) pm, b = 1062,26(12) pm, c = 651,93(6) pm, α = 96,638(9)°, β = 92,351(8)° und γ = 94,230(9)°, isotyp. Es liegen “isolierte” trigonalbipyramidale WO 5 -Gruppen vor, Koordinationszahl 5 und 6 fur K + . Der Madelunganteil der Gitterenergie und effektive Koordinationszahlen diese uber mittlere fiktive Ionenradien werden berechnet und diskutiert.