ISSN:
0044-2313
Keywords:
Lanthanum acetate
;
ammonium lanthanum acetate
;
synthesis
;
crystal structure
;
thermal behaviour
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Anhydrous Lanthanum Acetate, La(CH3COO)3, and its Precursor, ·NH4)3[La(CH3COO)6] · 1/2 H2O: Synthesis, Structures, Thermal BehaviourSingle crystals of (NH4)3[La(CH3COO)6] · ½ H2O are obtained by refluxing La2O3in (CH3COO)3 · 1.5 H2O with an excess of NH4CH3COO in methanol. The crystal structure (trigonal, R3, Z = 6, a = 1 365.0(3) pm, c = 2 360(1) pm, R = 0.088, Rw = 0.061 exhibits the coordination number of nine for La3+, which is surrounded by three chelating-type bidentate and three unidentate acetate groups. Characteristic are monomeric units of [La(CH3COO)6]3- which are connected to a three-dimensional network by hydrogen bonds with the NH4+ ions. Thermal decomposition consists of four steps with La(CH3COO)3, La2(CO3)3 and La2O2CO3 as intermediates and La2O3 as the final Product. Single crystals of La(CH3COO)3 are obtained from La2O3 in a melt of NH4CH3COO (molar ratio 1:12) in a sealed glass ampoule. The crystal structure (trigonal, R3, Z = 18, a = 2 203.0(5) pm; c = 987.1(3) pm, R = 0.027, Rw = 0.023) shows the coordination number of ten for La3+. These are three-dimensionally connected by oxygen atoms of the acetate groups with two tetradentate double-bridging and one Z,Z-type-bridging bidentate acetate group.
Notes:
(NH4)3[La(CH3COO)6] · 1/2 H2O erhält man in Form von Einkristallen durch Erhitzen von La2O3 bzw. La(CH3COO)3 · 1,5 H2O mit einem Überschuß von Ammoniumacetat in Methanol. Die Röntgenstrukturanalyse (trigonal, R3, Z = 6, a = 1 365,0(3) pm, a = 2 360(1) pm, R = 0,088, Rw = 0,061 zeigt, daß La3+ von jeweils drei „chelating-type bidentate“- bzw. „unidentate“-Acetatgruppen umgeben ist (Koordinationszahl neun). Die Kristallstruktur wird von monomeren anionischen Baueinheiten [La(CH3COO)6]3- bestimmt, welche über Wasserstoffbrückenbindungen mit den NH4+-Ionen zu einer dreidimensionalen Struktur verknüpft sind. Der thermische Abbau verläuft in vier Stufen über La(CH3COO)3, La2(CO3)3 und La2O2CO3 zu La2O3. Einkristalle von La(CH3COO)3 erhält man aus einer Schmelze von La2O3 in NH4CH3COO (molares Verhältnis 1:12) in einer abgeschmolzenen Glasampulle. Die Röntgenstrukturanalyse (trigonal, R3, Z = 18, a = 2 203,0(5) pm; c = 987,1(3) pm, R = 0,027, Rw = 0,023) ergibt für La3+ die Koordinationszahl zehn. Die La3+-Ionen sind dreidimensional über die Sauerstoffatome der Acetatgruppen verknüpft, Pro La3+ zwei „tetradentate double-bridging“-Acetatgruppen und eine „Z,Z-type-bridging bidentate“-Acetatgruppe.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19936190916
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