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  • 1
    ISSN: 0044-2313
    Keywords: Chromium(II)-orthophosphate ; crystal growth ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Beiträge zum thermischen Verhalten und zur Kristallchemie von wasserfreien Phosphaten. XIX. Tri-chrom(II)-bis-phosphat Cr3(PO4)2 (≙ Cr6(PO4)4) - Ein Übergangsmetall(II)- Orthophosphat mit neuem StrukturtypIntensiv blau-violette Kristalle des bislang unbekannten Tri-chrom(II)-bis-phosphats, Cr3(PO4)2, entstehen bei der Reduktion von CrPO4 mit Chrom oberhalb von 1050°C (evakuierte Quarzglasampullen, wenige mg NH4I oder I2 als Mineralisator). Die Kristallstruktur von Cr3(PO4)2 enthält sechs kristallographisch unabhängige Cr2+ in der Elementarzelle (P212121, Z = 8, a = 8,4849(10) Å, b = 10,3317(10) Å, c = 14,206(3) Å). Davon sind fünf in der ersten Koordinationssphäre von vier Sauerstoffatomen leicht verzerrt quadratisch-planar umgeben (1,96 Å ≤ d(Cr—O) ≤ 2.15 Å). Deren Koordination wird vervollständigt durch zwei bzw. drei weiter entfernte Sauerstoffatome (2,32 Å ≤ d(Cr—O) ≤ 3,21 Å). Das sechste Cr2+-Ion ist stark verzerrt oktaedrisch koordiniert (d(Cr—O): 1,97, 2,04, 2,15, 2,28, 2,29, 2,53 Å).Die vier kristallographisch unterschiedlichen [PO4]-Gruppen zeigen nur geringe Abweichungen von der Geometric eines idealen Tetraeders (1,51 Å ≤ d(P—O) ≤ 1,57 Å; 104,3° ≤ ∠(O—P—O) ≤ 114,4°).Für die Cr2+ wurde mit μexp = 4,28(2) μB (θP = -54,8(5) K) ein ungewöhnlich niedriges mittleres magnetische Moment gefunden.
    Notes: Deep blue-violet single crystals of hitherto unknown chromous orthophosphate have been obtained reducing CrPO4 by elemental Cr at temperatures above 1050°C in evacuated silica ampoules (NH4I or I2 as mineraliser). The complex structure of Cr3(PO4)2 (P212121, Z = 8, a = 8.4849(10) Å, b = 10.3317(10) Å, c = 14.206(2) Å) contains six crystallographically independent Cr2+ per unit cell. Five of them are coordinated by four oxygen atoms which form a distorted (roof shaped) square plane as first coordination sphere at interatomic distances 1.96 Å ≤ d(Cr—O) ≤ 2.15 Å. Their coordination is completed by additional oxygen atoms (2 or 3) at distances 2.32 Å ≤ d(Cr—O) ≤ 3.21 Å. The sixth Cr2+ shows six-fold octahedral coordination with strong radial distortion (d(Cr—O): 1.97, 2.04, 2.15, 2.28, 2.29, 2.53 Å).The four different [PO4] groups exhibit only minor deviations from ideal tetrahedral geometry (1.51 Å ≤ d(P—O) ≤ 1.57 Å, 104.3° ≤ ∠(O—P—O) ≤ 114.4°).An unusually low magnetic moment μexp = 4.28(2) μB (θP = -54.8(5) K) has been observed for Cr2+.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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