Über die Amide des Europiums und Ytterbiums

Abstract

Eu(NH2)2, Yb(NH2)2 (76,2proz. mit 23,8% Yb(NH2)3) und Yb(NH2)3 wurden durch Umsetzung der Metalle mit Ammoniak unter verschiedenen Reaktionsbedingungen als röntgenkristalline Präparate dargestellt. Eu(NH2)2 und Yb(NH2)2 kristallisieren tetragonal im Anatas‐Gitter mit den Gitterkonstanten a = 5,450 Å, c = 10,861 Å, c/a = 1,993 bzw. a = 5,193 Å, c = 10,419 Å, c/a = 2,006; Raumgruppe D 194h—I41/amd. Die IR‐Spektren der Amide wurden gemessen (280–4000 cm−1) und zugeordnet. Von Eu(NH2)2 wurde weiterhin das Remissionsspektrum (4000–38000 cm−1) aufgenommen und gedeutet; die Temperaturabhängigkeit der magnetischen Suszeptibilität des Eu(NH2)2 wurde bestimmt (μ = 7,80 BM). Durch thermische Zersetzung von Eu(NH2)2 wurde bei 250°C kristallines EuN (a = 5,019 Å) dargestellt, durch thermischen Abbau von Yb(NH2)3 bei 240°C wurde eine Phase der Zusammensetzung Yb0,66(NH) festgestellt, die im NaCl‐Gitter (a = 4,85 Å) kristallisiert und deren Homogenitätsbereich sich bis zum stöchiometrischen YbN erstreckt.

Chemistry of Ammonothermal Synthesis

“…Increasing the reaction conditions for Mg(NH 2 ) 2 from ∼0.09 MPa and ambient temperature to ∼10 MPa and 613-653 K reduces the reaction time from 1.5-2 years to two days and forms a micro crystalline product suitable for powder X-ray diffraction [115]. Mg(NH 2 ) 2 crystals were obtained from Mg metal under ammonobasic conditions (using NaNH 2 or NaN 3 as mineralizers) at 523-653 K and 10-345 MPa [1,2,115] [123] and Sm(NH 2 ) 3 [121], La(NH 2 ) 3 [120] is the only binary trivalent rare-earth metal amide so far. Colorless single crystals are obtained from the reaction of lanthanum metal and potassium (molar ratio 80:1) in supercritical ammonia at 623 K and 405 MPa after six days.…”

“…A few imides and nitride imides were obtained from ammonothermal conditions, but only in the form of micro crystalline powders, see Table 8. From the thermal degradation of ternary rare-earth metal amides the formation of Yb 0.66 (NH) [123], Ce 3 (NH) 3 N [76] and La 0.667 NH [172] was reported. The reaction of Mg 3 N 2 with NH 3 at T ≥ 773 K and p ≥ 5 MPa yields MgNH with Mg(NH 2 ) 2 and Mg 3 N 2 impurities after one week.…”

Octaammine EuII and YbII Azides and Their Thermal Decompositions to the Nitrides

“…By the reaction of organometallic precursors, such as (ammine)tris(η 5 ‐cyclopentadienyl)ytterbium(III) or its amido derivative, with LiNH 2 nanocrystalline YbN was synthesized at only 250 °C . Also, the thermal decomposition of europium(II) amide yielded the nitride at only 250 °C …”

“…[30] Also, the thermal decomposition of europium(II) amide yielded the nitride at only 250°C. [32] Bulky ligands on lanthanoid atoms have been frequently employed to lend lanthanoid azides more stability towards mechanical shock or temperature changes, and also to increase the solubility in organic and unipolar solvents. Targets of these works are the preparation of phosphors or of molecular nitrides of the lanthanoids, which still seem to be elusive.…”

The Utilization of Solid State Chemistry Reaction Routes as New Syntheses Strategies for the Coordination Chemistry of Rare Earth Amides

“…As this report shows the variety of products from the oxidation of rare earth metals in liquid ammonia is even more diversified. As the formation of amides [Ln(NH 2 ) x ] and nitrides LnN in liquid ammonia demonstrates [42,43,52,53], autoprotolysis of ammonia and participation of NH 3 molecules, NH 2 Ϫ and N 3Ϫ anions in the coordination of the metal centres in addition to N-heterocyclic amines further increase the variability of the amide products obtained.…”