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(Mg1–xCrx)2P2O7, CaCrP2O7, SrCrP2O7 und BaCrP2O7 – Neue Diphosphate des zweiwertigen Chroms

2001; Wiley; Volume: 627; Issue: 9 Linguagem: Inglês

10.1002/1521-3749(200109)627

1521-3749

Kai Maaß, Robert Glaum, R. Gruehn,

Organometallic Compounds Synthesis and Characterization

In den Systemen A2P2O7/Cr2P2O7 (A = Mg, Ca, Sr, Ba) wurden die Mischkristallreihe Mg2P2O7–Cr2P2O7 sowie CaCrP2O7, SrCrP2O7 und BaCrP2O7 erstmalig synthetisiert und charakterisiert. Die Mischkristallreihe (Mg1–xCrx)2P2O7 ist im gesamten Bereich (0,01 < x < 0,94; T = 950 °C) isotyp zu den Randphasen β-Mg2P2O7 und β-Cr2P2O7; sie zeigte während der Abkühlung auf Raumtemperatur keine Umwandlung (β → α) in eine Tieftemperaturphase wie bei Mg2P2O7 und Cr2P2O7. Die diskreten Phasen CaCrP2O7 (A), SrCrP2O7 (B) und BaCrP2O7 (C) in den weiteren quasibinären Systemen sind untereinander strukturell nicht verwandt, aber jeweils isotyp zu den bekannten Cobaltverbindungen [(A): P-1, Z = 2, a = 6,312(2) Å, b = 6,499(2) Å, c = 6,916(2) Å, α = 83,12(3)°, β = 88,37(3)°, γ = 67,72(3)°, 3235 unabhängige Reflexe, R1 = 0,041, wR2 = 0,112; (C): P-1, Z = 2, a = 5,382(8) Å, b = 7,271(8) Å, c = 7,589(4) Å, α = 103,33(7)°, β = 89,91(9)°, γ = 93,6(1)°, 1571 unabhängige Reflexe, R1 = 0,085, wR2 = 0,31]. Über SrCrP2O7 haben wir bereits früher berichtet. Die Cr2+-Ionen in (A) sind verzerrt-oktaedrisch, in (B) und (C) quadratisch-pyramidal koordiniert. Die Ergebnisse von UV/VIS-spektroskopischen und magnetischen Messungen wie auch die IR-Spektren der Diphosphate werden mitgeteilt. Contributions on Crystal Chemistry and Thermal Behaviour of Anhydrous Phosphates. XXXI. (Mg1–xCrx)2P2O7, CaCrP2O7, SrCrP2O7 and BaCrP2O7 – New Diphosphates of Divalent Chromium In the quasi-binary systems A2P2O7/Cr2P2O7 (A = Mg, Ca, Sr, Ba) the solid solution (Mg1–xCrx)2P2O7 as well as the new compounds CaCrP2O7, SrCrP2O7, and BaCrP2O7 have been synthesized and characterized for the first time. In the whole experimental range (0.01 < x < 0.94; T = 950 °C) the solid solution (Mg1–xCrx)2P2O7 is isotypic to the pure phases β-Mg2P2O7 and β-Cr2P2O7; but no phase transition (β → α) to a low-temperature modification, as in Mg2P2O7 and Cr2P2O7, was found. CaCrP2O7 (A), SrCrP2O7 (B), and BaCrP2O7 (C), phases without detectable homogenity range in the other quasi-binary systems are not structurally related to each other, but are isotypic to the corresponding compounds containing cobalt. [(A): P-1, Z = 2, a = 6.312(2) Å, b = 6.499(2) Å, c = 6.916(2) Å, α = 83.12(3)°, β = 88.37(3)°, γ = 67.72(3)°, 3235 independent reflections, R1 = 0.041, wR2 = 0.112; (C): P-1, Z = 2, a = 5.382(8) Å, b = 7.271(8) Å, c = 7.589(4) Å, α = 103.33(7)°, β = 89.91(9)°, γ = 93.6(1)°, 1571 independent reflections, R1 = 0.085, wR2 = 0.31]. We have reported earlier details on SrCrP2O7. The coordination of Cr2+ by oxygen is distorted octahedral in (A), while in the structures of (B) and (C) square-pyramidal environment is found. The results of UV/VIS-spectroscopic and magnetic measurements as well as IR-spectra of the diphosphates are reported.