Olaf Reckeweg

About binary and ternary alkaline earth metal nitrides

Binary and ternary alkaline earth metal nitrides compounds have been synthesized and characterized by the means of X-ray structure analysis. By the reaction of the alkaline earth metals Be, Mg, and Ca with dry nitrogen, we obtained crystalline material of Be3N2 (1), Mg3N2 (2), and Ca3N2 (3), respectively. For these three compounds we could confirm the cubic anti bixbyite structure (Ia3 (#206); 1: a = 814.92(1) pm; 2: 997.26(6) pm and 3: a = 1147.86(2) pm). By reacting 1 : 2 : 1 mixtures of Ae (Ae = Ca, Sr) : Mg : NaN3 we synthesized the ternary nitrides CaMg2N2 (4) and SrMg2N2 (5). We confirmed the structural data obtained by Rietveld-analysis of X-ray powder diffraction data for 4 and found 5 to be isotypic (anti-C–M2O3 structure, trigonal, P 3ml (#164); 4: a = 354.77(5) pm, c = 609.60(12) pm; 4: a = 362.20(5), c = 635.90(13) pm). The indexing of the powder diffractogram of “Ca3Mg3N4” and refining the lattice parameters (hexagonal, a = 352.9(2) and c = 607.5(5) pm) suggest its identity with 4. The black “low-temperature phase of Ca3N2” has been synthesized and and the X-ray powder diffractogram has been recorded. The reactions of this phase are also described. The yellow “high-temperature phase of Ca3N2” was found to be Ca4N2(CN2).

Alkaline earth metal nitride compounds with the composition M2NX (M=Ca, Sr, Ba; X=□, H, Cl or Br)

Abstract The alkaline earth metal nitride compounds Ca 2 N, Sr 2 N, (Sr 0.48 Ba 0.52 ) 2 N, Ba 2 N, Sr 2 NCl and Sr 2 NBr have been synthesized and investigated by the means of X-ray diffraction. These compounds all have crystal structures closely related to the anti- α -NaFeO 2 structure type. The reaction products obtained from the nominal starting compositions “Ca 2 NH x ” (0⩽ x ⩽1) were also analyzed by X-ray powder diffraction. With x ⩾0.75, Ca 2 NH 1− δ is the only product observed, but for x 2 N is found in equilibrium with Ca 2 NH 1− δ . An overview of M 2 NX and alkaline earth metal subnitride compounds compares the present results to literature data.

Über die Koexistenz von tetragonalem und monoklinem CaC2: Strukturelle und spektroskopische Untersuchungen an Erdalkalimetallacetyliden, MC2 (M = Ca, Sr, Ba)

Fur die Erdalkalimetallacetylide CaC2, SrC2 und BaC2 kann die Existenz von jeweils drei polymorphen Strukturen angenommen werden, die monokline Tieftemperaturform, die tetragonale Form und die kubische Hochtemperaturform. Einkristallstrukturanalysen und 13C-MAS-NMR-Messungen ergaben, das die C22–-Ionen in den tetragonalen Strukturen axialsymmetrisch angeordnet sind. Allerdings enthielten die von uns synthetisierten CaC2-Proben stets Anteile von monokliner und tetragonaler Phase. Raman-Spektren von CaC2-Proben zeigten die Prasenz zweier verschiedener C2-Streckschwingungsbanden. Die aus der Koexistenz dieser beiden Phasen resultierende Problematik bei der Interpretation von 13C-MAS-NMR-Spektren wird diskutiert. On the Coexistence of Tetragonal and Monoclinic CaC2: Structural and Spectroscopic Studies on Alkaline Earth Metal Acetylides, MC2 (M = Ca, Sr, Ba) The alkaline earth acetylides CaC2, SrC2 and BaC2 can be considered to occur in three polymorphic structures each. The monoclinic low-temperature form, the tetragonal form, and the cubic high-temperature form. No deviation from axial symmetry is obtained for the C22– ions in the tetragonal structure determinations, as confirmed by X-ray single-crystal structures and 13C MAS NMR studies. The CaC2 samples prepared by us were always a mixture of monoclinic and tetragonal phase. Their Raman spectra exhibited two distinct C2 streching vibrations. Problems arising from the coexistence of these two phases for the interpretation of 13C MAS NMR spectra are discussed.

Ca11N6(CN2)2 and Ca4N2(CN2): The True Nature of an “Unusual Binary Nitride” Is Finally Revealed

One calcium nitride less! Several different binary nitrides of calcium have been reported: Ca(3)N(2), Ca(2)N, Ca(3)N(4), and Ca(11)N(8). X-ray structural analysis and spectroscopy revealed the latter is actually calcium nitride cyanamide and one of, so far, two examples of a new class of ternary phases (see boxes in the phase diagram).

Magnesium nitride chemistry

Abstract Experiments in the system RE–Mg–N (RE=La, Ce, Gd) have been done to explore the possible synthesis of nitrides using Mg as reactive melt and to extend the number of known nitride compounds containing Mg. Since these experiments produce only binary nitrides, we explored the use of mixed Na/Mg melts and discovered the quarternary nitrides BaMg 3.33 Nb 0.67 N 4 ( 1 ), BaMg 3.33 Ta 0.67 N 4 ( 2 ) and Eu 4 TaMgN 5 ( 3 ), which were characterized by single crystal structure analysis. The BaMg 3.33 M 0.67 N 4 compounds are isotypic to UCr 4 C 4 [R.K. Behrens, W. Jeitschko, Monatsh. Chem. 118 (1987) 43–50] (filled MoNi 4 type [D. Harker, J. Chem. Phys. 12 (1944) 315–317]) and crystallize in the space group I 4/ m (#87) with the lattice parameters a =856.40(12) and c =353.90(7) pm for ( 1 ), and a =859.61(8) and c =354.21(5) for ( 2 ). ( 3 ) crystallizes in a new structure type in the acentric orthorhombic space group Pna 2 1 (#33) with the lattice parameters a =1265.5(3), b =1015.9(2) and c =692.5(1) pm.

Ag8Ca19N7 – Nitrogen Bridged Ca19N7 Superoctahedra surrounded by Silver Tetrahedra

By reacting Ca3N2 and silver powder at a temperature of 1300 K the subnitride Ag8Ca19N7 was obtained. The title compound crystallizes in the space group Fm3m (No. 225) and has the lattice constant a = 1472.0(2) pm at T = 210 K and a = 1474.43(3) pm at T = 295 K. Ag8Ca19N7 combines two very interesting, but rather different structural features, Ag4 tetrahedra and Ca19N7 superoctahedra. An analysis of the bonding situation has been performed by means of Extended-Huckel calculations. Ag8Ca19N7 – Stickstoff-verbruckte Ca19N7-Superoktaeder umgeben von SilberTetraedern Durch die Reaktion von Ca3N2 und Silberpulver bei einer Temperatur von 1300 K wurde das Subnitrid Ag8Ca19N7 erhalten. Die Titelverbindung kristallisiert in der Raumgruppe Fm3m (Nr. 225) mit der Gitterkonstanten a = 1472.0(2) pm (T = 210 K) und a = 1474.43(3) pm (T = 295 K). In Ag8Ca19N7 sind zwei interessante, aber verschiedene Strukturelemente vereint: Ag4-Tetraeder und Ca19N7-Superoktaeder. Eine Analyse der Bindungsverhaltnisse wurde mit der Extended-Huckel-Methode durchgefuhrt.

The Nitrido Borates Ln3B2N4 (Ln = La-Nd) and La5B4N9: Syntheses, Structures, and Properties

Single crystals of the lanthanoide nitrido borates Ln3B2N4 (Ln = La–Nd) and La5B4N9 have been obtained from reactions of lanthanoide metal powder, lanthanoide nitride powder, and hexagonal boron nitride in calcium chloride melts. The isotypic compounds Ln3B2N4 belong to the space group Immm (#71), Z = 2, with the lattice parameters for La3B2N4: a = 362.94(3), b = 641.25(6), c = 1097.20(8) pm; Ce3B2N4: a = 356.20(3), b = 631.90(6), c = 1071.91(8) pm; Pr3B2N4: a = 353.46(4), b = 630.04(13), c = 1079.04(23) pm and Nd3B2N4: a = 351.52(4), b = 627.01(15), c = 1075.59(23) pm. The structure of La5B4N9 has been determined in the space group Pbcm (#57), Z = 4, with a = 988.25(5); b = 1263.48(7), c = 770.33(4) pm. These two structure types resemble three kinds of nitrido borate anions, the oxalate analogue B2N4 of Ln3B2N4, and the carbonate analogue BN3 together with the six-membered ring system B3N6 of La5(BN3)(B3N6). In contrast to the valence compound La5B4N9 the compounds (Ln3+)3(B2N4)8–(e–) contain one electron in the conduction band, yielding temperature independent paramagnetism for La3B2N4. The calculated electronic structure is developed through the formation of B2N48– ions by dimerisation of two BN2 units. Die Nitridoborate Ln3B2N4 (Ln = La–Nd) und La5B4N9: Synthesen, Strukturen und Eigenschaften Einkristalle der Lanthanoidnitrodoborate Ln3B2N4 (Ln = La–Nd) und La5B4N9 wurden durch Reaktionen von Lanthanoid-Metallpulver, Lanthanoidnitrid-Pulver mit hexagonalem Bornitrid in Schmelzen aus Calciumchlorid dargestellt. Die isotypen Verbindungen Ln3B2N4 kristallisieren in der Raumgruppe Immm (Nr. 71), Z = 2, mit den Gitterkonstanten fur La3B2N4: a = 362.94(3), b = 641.25(6), c = 1097.20(8) pm; Ce3B2N4: a = 356.20(3), b = 631.90(6), c = 1071.91(8) pm; Pr3B2N4: a = 353.46(4), b = 630.04(13), c = 1079.04(23) pm und Nd3B2N4: a = 351.54(2), b = 627.01(15), c = 1075.59(23) pm. La5B4N9 kristallisiert in der Raumgruppe Pbcm (Nr. 57), Z = 4, mit a = 988,25(5); b = 1263,48(7), c = 770,33(4) pm. Diese zwei Strukturtypen enthalten drei verschiedene Nitridoborat Anionen, das Oxalat-analoge B2N4 von Ln3B2N4 und das Carbonat-analoge BN3 zusammen mit dem sechsgliedrigen Ringsystem B3N6 von La5(BN3)(B3N6). Anders als die Valenzverbindung La5B4N9 enthalten die Verbindungen (Ln3+)3(B2N4)8–(e–) ein Elektron im Leitungsband. Fur La3B2N4 resultiert temperaturunabhangiger Paramagnetismus. Die berechnete elektronische Struktur von La3B2N4 wird durch die Bildung von B2N48–-Ionen aus zwei BN2-Einheiten abgeleitet.

Orthorhombic Ba3[BN2]2: a new structure type for an alkaline earth metal nitrido borate

Abstract Yellow, transparent single crystals of Ba 3 [BN 2 ] 2 (P2 1 2 1 2 1 (No. 19), a =424.73(2), b =1105.60(4) and c =1475.72(6) pm, Z =4) are obtained by the reaction of Ba 2 N and BN in arc-welded Nb ampoules at 1300 K. The title compound crystallizes, despite its familiar 3:2:4 stoichiometry, in a new structure type. The vibrational spectra of orthorhombic Ba 3 [BN 2 ] 2 have been measured and assigned. The IR spectrum reveals strong band splitting arising from the low site symmetry and the presence of two different sets of crystallographically independent [BN 2 ] 3− groups. The new structure and the vibrational data are compared with those previously reported for the cubic form of Ba 3 [BN 2 ] 2 .

Ca11N6(CN2)2 und Ca4N2(CN2): Die wahre Natur eines „ungewöhnlichen binären Nitrids” wird enthüllt

Ein Calciumnitrid weniger! Einige binare Calciumnitride sind bisher beschrieben worden: Ca3N2, Ca2N, Ca3N4 und Ca11N8. Rontgenstrukturanalysen und spektroskopische Befunde sprechen aber dafur, dass es sich bei der zuletzt genannten Verbindung tatsachlich um ein Calciumnitridcyanamid handelt und damit um eines von bisher zwei Beispielen einer neuen Klasse ternarer Phasen (siehe Kasten im Phasendiagramm).

Die Synthese und Struktur von Clusteraziden: A4[Nb6Cl12(N3)6](H2O)2 mit A=Rb. Cs / Synthesis and Structure of the Cluster Azides: A4Nb6Cl12(N3)6](H2O)2 with A=Rb, Cs

Abstract The new compounds A4[Nb6Cl12(N3)6](H2O)2 (A = Rb, Cs) were synthesized from In4[Nb6Cl12Cl6] by substituting six terminal Cl ligands and the In+ ions in methanolic solution. An X-ray structure refinement was performed on single-crystal data of Rb4[Nb6Cl12(N3)6](H2O)2 (1) (space group P1̄, Z = 1, a = 912.5(1) pm, b = 937.2(1) pm, c = 1062.0(1) pm, α = 96.88(2)°, β = 101.89(1)°, γ = 101.44(2)°) and Cs4[Nb6Cl12(N3)6](H2O)2 (2) (space group PI, Z = 1, a = 920.9(5) pm, b = 947.9(7) pm, c = 1091.8(7) pm, α = 96.89(6)°, β = 103.35(5)°, γ = 101.60(5)°. Each of the centrosymmetric [Nb6Cl12(N3)6]4- ions of the isotypic compounds contains six terminal azide groups at the corners of the octahedral niobium cluster (d̄Nb-N = 226(1) pm (1), 225(1) pm (2), bond angles Nb-N-N 120-127°). The [Nb6Cl12(N3)6]4- ions are linked via Rb-N and Rb-Cl interactions of the Rb+ ions to form a three-dimensional structure. Crystals of the compounds react explosively on heating or mechanical pressure.