Synthesis and crystal structure of monoclinic Fe2(SeO4)3

Summary Crystals of monoclinic Fe₂(SeO₄)₃ were synthesized under hydrothermal conditions. The structure was determined by single crystal X-ray methods and refined in space group P2₁/n with 2 646 independent reflections (sin /<0.7 Å^–1) toR=0.033,R _w=0.037:a=8.530 (2) Å,b=8.888 (2) Å,c=11.952 (2) Å, =91.13 (1)°,V=906.0 ų,Z=4. The crystal structure is isotypic with the monoclinic modification of Fe₂(SO₄)₃, containing two different Fe(III) and three Se(VI) atomic positions. The FeO₆ and SeO₄ polyhedra are only slightly distorted, the mean Fe-O bond lengths are 1.986 Å and 2.004 Å, the average distances within the SeO₄ tetrahedra are each 1.628 Å. The isolated FeO₆ octahedra only share corners with SeO₄ tetrahedra to build a framework structure.

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Synthese und Kristallstruktur von monoklinem Fe₂(SeO₄)₃

Zusammenfassung Kristalle von monoklinem Fe₂(SeO₄)₃ wurden unter Hydrothermalbedingungen gezüchtet. Die Struktur wurde mit Einkristall-Röntgenmethoden bestimmt und in der Raumgruppe P2₁/n mit 2 646 unabhängigen Reflexen (sin /<0.7Å^–1) aufR=0.033,R _w=0.037 verfeinert:a=8.530(2) Å,b=8.888(2) Å,c=11.952(2) Å, =91.13(1)°,V=906.0 ų,Z=4. Die Kristallstruktur ist isotyp mit der monoklinen Modifikation von Fe₂(SO₄)₃, sie enthält zwei unterschiedliche Fe(III) und drei Se(VI) Atompositionen. Die FeO₆-Polyeder sind nur gering verzerrt, die mittleren Fe-O Bindungslängen sind 1.986 Å und 2.004 Å, die mittleren Abstände in den SeO₄-Tetraedern sind jeweils 1.628 Å. Die isolierten FeO₆-Oktaeder sind nur über gemeinsame Ecken mit SeO₄-Tetraedern verbunden, wobei eine Gerüststruktur entsteht.

     

PbCu3(OH)(NO3)(SeO3)3·1/2H2O und Pb2Cu3O2(NO3)2(SeO3)2: Synthese und Kristallstrukturuntersuchung

Crystals of PbCu₃(OH)(NO₃)(SeO₃)₃·1/2H₂O [a=7.761(3)Å,b=9.478(4)Å,c=9.514(4)Å, =66.94(2)°, =69.83(2)°, =81.83(2)°, space group P ,Z=2] and Pb₂Cu₃O₂(NO₃)₂(SeO₃)₂ [a=5.884(2)Å,b=12.186(3)Å,c=19.371(4)Å, space group Cmc2₁,Z=4] were synthesized under hydrothermal conditions. Their crystal structures were refined with three-dimensional X-ray data toR _w=0.033 resp. 0.055. In PbCu₃(OH)(NO₃)(SeO₃)₃·1/2H₂O the Cu atoms are [4+1] and [4+2] coordinated and via SeO₃ groups a three-dimensional atomic arrangement is built up. In Pb₂Cu₃O₂(NO₃)₂(SeO₃)₂ there are sheets, which are connected only via Pb-O bonds ranging from 2.98 Å to 3.16 Å.

     

Crystal structure of synthetic Cu3SeO4(OH)4

Summary The crystal structure of synthetic Cu₃SeO₄(OH)₄ was determined by single crystal X-ray methods:a=8.382 (2) Å,b=6.087 (1) Å,c=12.285 (2) Å,V=626.8 ų,Z=4, space group Pnma,R=0.026,R _w =0.021 for 1255 independent reflections (sin / 0.8 Å^–1). The crystal structure is isotypic to that of the mineral antlerite, Cu₃SO₄(OH)₄. The copper atoms are Jahn-Teller distorted with Cu^[4+2]O₆ polyhedra forming triple chains along [010]. These chains are linked via SeO₄ tetrahedra and weak hydrogen bonds to a framework structure.

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Die Kristallstruktur von synthetischem Cu₃SeO₄(OH)₄

Zusammenfassung Die Kristallstruktur von synthetischem Cu₃SeO₄(OH)₄ wurde mittels Einkristall-Röntgenmethoden ermittelt:a=8.382 (2) Å,b=6.087 (1) Å,c=12.285 (2) Å,V=626.8 ų,Z=4, Raumgruppe Pnma,R=0.026,R _w =0.021 für 1255 unabhängige Reflexe (sin / 0.8 Å^–1). Die Kristallstruktur ist isotyp mit der des Minerals Antlerit, Cu₃SO₄(OH)₄. Die Kupferatome sind Jahn-Teller-verzerrt, die Cu^[4+2]O₆ Polyeder bilden Dreierketten entlang [010]. Diese Ketten sind über SeO₄-Tetraeder und schwache Wasserstoffbrücken zu einer Gerüststruktur verbunden.

     

Die Kristallstrukturen der Kupfer(II)-oxo-selenite Cu2O(SeO3) (kubisch und monoklin) und Cu4O(SeO3)3 (monoklin und triklin)

Syntheses within the system CuO-SeO₂-H₂O revealed four copper(II)-oxo-selenites. The crystal structures of these compounds were determined by single crystal X-ray techniques. Chemical formulae, lattice parameters and space groups are: Cu₂O(SeO₃)-I [a=8.925 (1) Å, P2₁3], Cu₂O(SeO₃)-II [a=6.987 (5) Å,b=5.953 (4) Å,c=8.429 (6) Å, =92.17 (3)°, P2₁/n], Cu₄O(SeO₃)₃-I [a=15.990 (8) Å,b=13.518 (8) Å,c=17.745 (12) Å, =90.49 (5)°, P2₁/a], and Cu₄O(SeO₃)₃-II [a=7.992 (6) Å,b=8.141 (6) Å,c=8.391 (6) Å, =77.34 (3)°, =65.56 (3)°, =81.36 (3)°, ].All the Cu atoms are-with one exception-[4], [4+1], and [4+2] coordinated by O atoms. The four nearest O atoms are more or less distorted square planar arranged. Within the CuO₄ squares the Cu-O bond lengths are significantly shorter for the [4] coordinated O atoms as compared with those of the [4+1] and [4+2] coordinated Cu atoms. The exception in the coordination of the Cu atoms is the Cu(1) atom in Cu₂O(SeO₃)-I with the site symmetry 3, which is trigonal dipyramidal [5] coordinated. A common feature of these four crystal structures is, that O atoms outside the SeO₃ groups are tetrahedrally coordinated by four Cu(II) atoms. The Se atoms are as usual [3] coordinated, building up SeO₃ pyramids. In all these four compounds the copper-oxygen polyhedra are combined to a three-dimensional network.

     

The crystal structure of ZnFe 2 3+ (SeO3)4

Summary The new synthetic compound ZnFe ₂ ³⁺ (SeO₃)₄ forms at low-hydrothermal conditions at 220 °C. It belongs to the monoclinic system; the structure was determined by single-crystal X-ray diffraction in the space group Pc. The unit cell data are:a=8.196(4) Å,b=7.997(4) Å,c=8.033(4) Å, =92.27(3)°,V=526.1 ų;Z=2. The structure of ZnFe ₂ ³⁺ (SeO₃)₄ contains two types of FeO₆ octahedra, one distorted ZnO₅ trigonal bipyramid, and four selenite groups. Formal clusters consisting of the ZnO₅ group, edge-linked with both FeO₆ groups and one SeO₃ pyramid, are connected by common corners, involving three further selenite groups to a framework structure.

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Die Kristallstruktur von ZnFe ₂ ³⁺ (SeO₃)₄

Zusammenfassung Die neue synthetische Verbindung ZnFe ₂ ³⁺ (SeO₃)₄ bildet sich bei niedrighydrothermalen Bedingungen (220°C). Die Kristallstruktur wurde mit Einkristallröntgenmethoden in der monoklinen Raumgruppe Pc gelöst. Die Zellparameter sind:a=8.196(4) Å,b=7.997(4) Å,c=8.033(4) Å, =92.27(3)°,V=526.1 ų;Z=2. Die Kristallstruktur von ZnFe ₂ ³⁺ (SeO₃)₄ weist zwei Arten von FeO₆-Oktaedern, eine verzerrte trigonale ZnO₅-Dipyramide sowie vier Selenitgruppen auf. Formal können Cluster, bestehend aus dem ZnO₅-Polyeder, kantenverknüpft mit den beiden FeO₆-Gruppen sowie einer SeO₃-Pyramide, beschrieben werden. Die Verknüpfung über Ecken zu einer Gerüststruktur erfolgt unter Beteiligung von drei weiteren Selenitgruppen.

     

Crystal structure of LiFe3+(SeO3)2

Summary Single crystals of LiFe³⁺(SeO₃)₂ were prepared by hydrothermal synthesis. The crystal structure of LiFe³⁺(SeO₃)₂ is reported: tetragonal, space group I 2d,a=10.649(2) Å,c=9.959(2) Å,V=1129.4 ų,Z=8, 1268 unique reflections,R=0.037. The structure contains LiFeO₈ groups, built up by FeO₆ octahedra edgesharing with strongly distorted LiO₄ tetrahedra. These LiFeO₈ groups share corners with trigonal pyramidal SeO₃ groups to form a three dimensional network. The mean bondlengths are 1.994 Å, 2.006 Å and 1.699 Å for Li-O, Fe-O and Se(IV)-O, respectively.

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Die Kristallstruktur von LiFe³⁺(SeO₃)₂

Zusammenfassung Einkristalle von LiFe³⁺(SeO₃)₂ wurden auf hydrothermalem Weg dargestellt und ihre Kristallstruktur bestimmt: tetragonal, Raumgruppe I 2d,a=10.649(2) Å,c=9.959(2) Å,V=1129.4 ų,Z=8, 1268 unabhängige Reflexe,R=0.037. Kennzeichnend für die Atomanordnung sind LiFeO₈ Gruppen, die aus FeO₆ Oktaedern und mit ihnen kantenverknüpften, stark verzerrten LiO₄ Tetraedern aufgebaut sind. Diese LiFeO₈ Baueinheiten bilden, mit trigonal pyramidalen SeO₃ Gruppen über Ecken verbunden, ein dreidimensionales Netzwerk. Die Mittelwerte der Li-O, Fe-O and Se(IV)-O Abstände sind 1.994 Å, 2.006 Å und 1.699 Å.

     

Darstellung und Kristallstruktur von Pb2(NO2)(NO3)(SeO3)

Crystals of Pb₂(NO₂)(NO₃)(SeO₃) were synthesized by partial reduction of nitrate ions with native copper under hydrothermal conditions. The crystal structure [a=5.529 (2) Å,b=10.357 (3) Å,c=6.811 (2) Å, space group Pmn2₁,Z=2] was determined from 1 707 independent X-ray data up to sin /=0.81 Å^–1 and was refined toR _w =0.028. The Pb(1) atom is ten coordinated to O atoms [Pb(1)-O from 2.51 Å to 2.96 Å], the Pb(2) atom has three nearest O atoms [Pb(2)-O=2.41 Å (1 ×) and 2.45 Å (2 ×)] and six next-nearest O atoms [Pb(2)-O from 2.80 Å to 3.22 Å].

Herrn Prof. Dr.K. Komarek zum 60. Geburtstag gewidmet.     

On the crystal chemistry of three copper(II)-arsenates: Cu3(AsO4)2-III,Na4Cu(AsO4)2, and KCu4(AsO4)3

The three copper(II)-arsenates were synthesized under hydrothermal conditions; their crystal structures were determined by single-crystal X-ray diffraction methods:Cu₃(AsO₄)₂-III:a=5.046(2) Å,b=5.417(2) Å,c=6.354(2) Å, =70.61(2)°, =86.52(2)°, =68.43(2)°,Z=1, space group ,R=0.035 for 1674 reflections with sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a=4.882(2) Å,b=5.870(2) Å,c=6.958(3) Å, =98.51(2)°, =90.76(2)°, =105.97(2)°,Z=1, space group ,R=0.028 for 2157 reflections with sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a=12.234(5) Å,b=12.438(5) Å,c=7.307(3) Å, =118.17(2)°,Z=4, space group C2/c,R=0.029 for 1896 reflections with sin / 0.80 Å^–1.Within these three compounds the Cu atoms are square planar [4], tetragonal pyramidal [4+1], and tetragonal bipyramidal [4+2] coordinated by O atoms; an exception is the Cu(2)^[4+1] atom in Cu₃(AsO₄)₂-III: the coordination polyhedron is a representative for the transition from a tetragonal pyramid towards a trigonal bipyramid. In KCu₄(AsO₄)₃ the Cu(1)^[4]O₄ square and the As(1)O₄ tetrahedron share a common O—O edge of 2.428(5) Å, resulting in distortions of both the CuO₄ square and the AsO₄ tetrahedron. The two Na atoms in Na₄Cu(AsO₄)₂ are [6] coordinated, the K atom in KCu₄(AsO₄)₃ is [8] coordinated by O atoms.Die drei Kupfer(II)-Arsenate wurden unter Hydrothermalbedingungen gezüchtet und ihre Kristallstrukturen mittels Einkristall-Röntgenbeugungsmethoden ermittelt:Cu₃(AsO₄)₂-III:a = 5.046(2) Å,b = 5.417(2) Å,c = 6.354(2) Å, = 70.61 (2)°, = 86.52(2)°, = 68.43(2)°,Z = 1, Raumgruppe ,R = 0.035 für 1674 Reflexe mit sin / 0.90 Å^–1.Na₄Cu(AsO₄)₂:a = 4.882(2) Å,b = 5.870(2) Å,c = 6.958(3) Å, = 98.51(2)°, = 90.76(2)°, = 105.97(2)°,Z = 1, Raumgruppe ,R = 0.028 für 2157 Reflexe mit sin / 0.90 Å^–1.KCu₄(AsO₄)₃:a = 12.234(5) Å,b = 12.438(5) Å,c = 7.307(3) Å, = 118.17(2)°,Z = 4, Raumgruppe C2/c,R = 0.029 für 1896 Reflexe mit sin / 0.80 Å^–1.Die Cu-Atome in diesen drei Verbindungen sind durch O-Atome quadratisch planar [4], tetragonal pyramidal [4 + 1] und tetragonal dipyramidal [4 + 2]-koordiniert; eine Ausnahme ist das Cu(2)^{[4 + 1]}-Atom in Cu₃(AsO₄)₂-III: Das Koordinationspolyeder stellt einen Vertreter des Übergangs von einer tetragonalen Pyramide zu einer trigonalen Dipyramide dar. In KCu₄(AsO₄)₃ haben das Cu(1)^[4]O₄-Quadrat und das As(1)O₄-Tetraeder eine gemeinsame O—O-Kante von 2.428(5) Å, was eine Verzerrung der beiden Koordinationsfiguren CuO₄-Quadrat und AsO₄-Tetraeder bedingt. Die zwei Na-Atome in Na₄Cu(AsO₄)₃ sind durch O-Atome [6]-koordiniert, das K-Atom in KCu₄(AsO₄)₃ ist [8]-koordiniert.

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Zur Kristallchemie dreier Kupfer (II)-Arsenate: Cu₃(AsO₄)₂-III, Na₄Cu(AsO₄)₂ und KCu₄(AsO₄)₃

     

Crystal structure of anhydrous alum RbFe3+(SeO4)2

Summary The compound RbFe(SeO₄)₂ was prepared hydrothermally by reaction of Rb₂CO₃ and FeC₂O₄·2H₂O with H₂O and H₂SeO₄ at 490 K. Single crystal X-ray methods revealed isotypy with KAl(SO₄)₂. RbFe(SeO₄)₂ crystallizes in space group P321;Z=1;a=5.005(1)Å,c=8.548(2) Å,V=185.4 ų; 781 unique data up to 80 °2;R,R _w =0.045, 0.042. The structure is best described as sheets of [Fe(SeO₄)₂]^– parallel (001), interconnected by Rb⁺. FeO₆ trigonal prims and SeO₄ tetrahedra have bond lengths of 1.99 Å and 1.63 Å, respectively. The Rb atom is [6 + 6] coordinated with Rb-O distances of 3.04 Å and 3.48 Å.

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Die Kristallstruktur des wasserfreien Alauns RbFe³⁺(SeO₄)₂

Zusammenfassung Die Verbindung RbFe(SeO₄)₂ wurde hydrothermal dargestellt durch Reaktion von Rb₂CO₃ und FeC₂O₄·2H₂O mit H₂O und H₂SeO₄ bei 490K. Einkristallröntgenmethoden belegten die Isotypie mit KAl(SO₄)₂ RbFe(SeO₄)₂ kristallisiert in der Raumgruppe P321;Z=1;a=5.005(1) Å,c=8.548(2) Å,V=185.4 ų; 781 unabhängige Daten bis 80 °2;R,R _w =0.045, 0.042. Die Struktur läßt sich am besten als Schichten von [Fe(SeO₄)₂]^– parallel (001) beschreiben, die durch Rb⁺ verbunden sind. FeO₆ trigonale Prismen und SeO₄ Tetraeder weisen Bindungslängen von 1.99 Å bzw. 1.63 Å auf. Das Rb-Atom ist [6+6] koordiniert mit Rb-O Abständen von 3.04 Å und 3.48 Å.

     

Crystal structures of Co3(SeO3)3·H2O and Ni3(SeO3)3·H2O,two new isotypic compounds

Summary The crystal structures of the new, hydrothermally synthesized, isotypic compounds Co₃(SeO₃)₃·H₂O and Ni₃(SeO₃)₃·H₂O were determined by direct and Fourier methods and refined toR _w=0.023, 0.032 using single crystal X-ray data up to sin/=0.81 Å^–1 [space group P ,a=8.102 (2), 7.986 (3) Å;b=8.219 (2), 8.133 (3) Å;c=8.572 (2), 8.422 (3) Å, =69.15 (1), 69.50 (1)°; =62.88 (1), 62.50 (1)°; =67.23 (1), 67.64 (1)°;Z=2]. The structures are built up from [Me ₅(SeO₃)₆·2H₂O]^2– sheets containing three crystallographically different types of octahedrally coordinatedMe ²⁺ and trigonal pyramidal coordinated Se⁴⁺ atoms, respectively. These sheets are linked only by a fourth type ofMe ^2+[6] atom. All coordination polyhedra deviate significantly from their ideal shapes, bond lengths within the extremly distortedMe(4)O₆ polyhedra range from 1.983 (2) Å to 2.403 (2) Å in Co₃(SeO₃)₃·H₂O and from 1.987 (4) Å to 2.301 (3) Å in the Ni compound, O-Se-O bond angles were found between 92.8 (2)° and 104.9 (1)°. Hydrogen bond lengths are 2.802 (3)Å and 2.600 (4)Å in the Co compound, and 2.762 (6) Å and 2.561 (6) Å in Ni₃(SeO₃)₃·H₂O. The latter is one of the shortest known hydrogen bonds donated by a water molecule.

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Die Kristallstrukturen von Co₃(SeO₃)₃·H₂O und Ni₃(SeO₃)₃·H₂O, zwei neue isotype Verbindungen

Zusammenfassung Die Kristallstrukturen der neuen, hydrothermal synthetisierten, isotypen Verbindungen Co₃(SeO₃)₃·H₂O und Ni₃(SeO₃)₃·H₂O wurden mit direkten und Fourier-Methoden bestimmt und unter Verwendung von Einkristallröntgendaten bis sin/=0.81 Å^–1 aufR _w-Werte von 0.023, 0.032 verfeinert [Raumgruppe P ,a=8.102 (2), 7.986 (3) Å;b=8.219 (2), 8.133 (3) Å;c=8.572 (2), 8.422 (3) Å, =69.15 (1), 69.50 (1)°; =62.88 (1), 62.50 (1)°; =67.23 (1), 67.64 (1)°;Z=2]. Die Strukturen werden von [Me ₅(SeO₃)₆·2H₂O]^2– Schichten aufgebaut, die je drei kristallographisch unterschiedliche Arten von oktaedrisch koordiniertenMe ²⁺ und trigonal pyramidal koordinierten Se⁴⁺ Atomen enthalten. Diese Schichten sind nur durch eine vierte Art vonMe ^2+[6] Atomen verknüpft. Alle Koordinationspolyeder weichen deutlich von ihren Idealformen ab, Bindungslängen in den extrem verzerrtenMe(4)O₆ Polyedern variieren zwischen 1.983 (2) Å und 2.403 (2) Å in Co₃(SeO₃)₃·H₂O und zwischen 1.987 (4) Å und 2.301 (3) Å in der Ni-Verbindung, O-Se-O-Bindungswinkel liegen zwischen 92.8 (2)° und 104.9 (1)°. Wasserstoffbrückenlängen sind 2.802 (3) Å und 2.600 (4) Å in der Co-Verbindung, und 2.762 (6) Å und 2.561 (6) Å in Ni₃(SeO₃)₃·H₂O. Letztere ist eine der kürzesten bekannten Wasserstoffbrücken eines Wassermoleküls.

     

The crystal structure of Fe(SeO2OH)(SeO4)·H2O

Summary The crystal structure of the hydrothermally synthesized compound Fe(SeO₂OH) (SeO₄) · H₂O was determined by single crystal diffraction methods:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 ų;Z=4, space group P2₁/c,R=0.029,R _w=0.027 for 2430 independent reflections (sin /0.76 Å^–1). Isolated FeO₅(H₂O)-octahedra share five corners with [SeO₂OH] and [SeO₄] groups to form sheets parallel to (100). These sheets are interconnected via hydrogen bonds only.

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Die Kristallstruktur von Fe(SeO₂OH)(SeO₄)·H₂O

Zusammenfassung Die Kristallstruktur der hydrothermal dargestellten Verbindung Fe(SeO₂OH) (SeO₄)·H₂O wurde mittels Einkristallbeugungsmethoden bestimmt:a=8.355(2) Å,b=8.696(2) Å,c=9.255(2) Å, =93.72(1)°,V=670.95 ų;Z=4, Raumgruppe P2₁/c,R=0.029,R _w=0.027 für 2 430 unabhängige Reflexe (sin / 0.76 Å^–1). Isolierte FeO₅(H₂O)-Oktaeder teilen fünf Ecken mit [SeO₂OH]- und [SeO₄]-Gruppen, wobei sie Schichten parallel (100) bilden. Diese Schichten sind nur über Wasserstoffbrücken miteinander verbunden.

     

Die Kristallstruktur von Cu7(OH)6(TeO3)2(SO4)2

The crystal structure of the new phase Cu₇(OH)₆(TeO₃)₂(SO₄)₂ [a=7.389 (1),b=7.638 (1),c=7.662 (2) Å, =75.17 (1), =75.90 (1), =84.19 (1)°;Z=1] was determined by direct methods andFourier summations from X-ray intensities, and was refined in space group P -C _i ¹ toR=0.039. As usual, the Cu(II) atoms are coordinated to four O atoms forming approximately a square with average Cu-O=1.96 (3) Å; one or two more distant O neighbours complete the coordination. The shape of the TeO₃ group is a rather clear-cut trigonal pyramid. A disorder was found for the SO₄ tetrahedra. The compound was synthesized under hydrothermal conditions [500 (10) K, saturation vapour pressure].

Herrn Prof. Dr.K. Komarek zum 60. Geburtstag gewidmet.     

Synthese und Strukturanalyse von Na3SbSe3·3Sb2O3·0,5Sb(OH)3

Investigations in the system Sb-Se-NaOH-H₂O, hydrothermal conditions, yielded crystals of the compound Na₃SbSe₃·3Sb₂O₃·0,5Sb(OH)₃. The structure of this compound (a=14.40 Å,c=5.568 Å; space group P 6₃-C ₆ ⁶ ;Z=2) was determined from 985 independent X-ray intensities — collected on an automaticWeissenberg type diffractometer — by thePatterson method and refined by the least squares method toR=8.3% (with -weighting 5.9%). The structure consists of SbO₃ pyramids which are connected via common oxygen corners to tubes parallel [001]. These tubes and SbSe₃ pyramids are combined by Na atoms to a framework. The Sb(OH)₃ groups are statistically located within the channels of the tubes.

     

Die Kristallstruktur von Dikalium-trikobalt(II)-dihydroxid-trisulfat-dihydrat,K2Co3(OH)2(SO4)3·2H2O

Crystals of K₂Co₃(OH)₂(SO₄)₃·2H₂O were synthesized under hydrothermal conditions. The crystal structure [a=17.945 (4) Å,b=7.557 (2) Å,c=9.760 (3) Å, space group Cmc2₁,Z=4] was determined by direct methods and refined with single crystal X-ray data. The H atoms were located byFourier syntheses. Their structural parameters were refined, too. The finalR-values areR=0.025 andR _w =0.028 (w=1/) for 612 reflections withF ₀>3 (F ₀). Both Co(II) atoms are octahedral six coordinated and form zigzag chains running parallel [001]. These chains are connected via sulfate groups to built up sheets parallel (100). The KO₉ polyhedron and one of the four hydrogen bonds link these sheets.

     

The thermal decomposition of (NH4)[VO(O2)2(NH3)]

The compound, (NH₄)[VO(O₂)₂(NH₃)], thermally decomposes to ammonium metavanadate, which then decomposes to vanadium pentoxide. Using a heating rate of 5 deg·min^–1, the first decomposition step occurs between 74° and 102°C. The transformation degree dependence of the activation energy (-E) is shown to follow a decreasing convex form, indicating that the first decomposition step is a complex reaction with a change in the limiting stage of the reaction. Infrared spectra indicated that the decomposition proceeds via the gradual reduction of the ratio of the (NH₄)₂O to V₂O₅ units from the original 11 ratio in ammonium metavanadate, which may be written as (NH₄)₂O·V₂O₅, to V₂O₅.The assistance of Professor A. M. Heyns (University of Pretoria) and Professor K. L. Range (University of Regensburg) is gratefully acknowledged as well as the financial assistance of the University of Pretoria and the FRD.     

Syntheses and crystal structures of NH4Ag2(AsS2)3 and (NH4)5Ag16(AsS4)7 with a discussion of (NH4)Sx polyhedra

Summary The atomic arrangements within the structures of NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; space group P2₁/n;R(F)=0.042] and (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; space group Cc;R(F)=0.073] were determined from single crystal X-ray data. In these two compounds the coordination spheres of the Ag atoms are quite different. In NH₄Ag₂(AsS₂)₃, the Ag atoms exhibit a [2+2]- and a [3+1]-coordination to S atoms up to 3.3 Å and with Ag atom neighbours at 2.93 Å and 3.05 Å respectively. In (NH₄)₅Ag₁₆(AsS₄)₇, the Ag atoms are — with one exception- [4] coordinated (Ag-S<3.3 Å) and the distances to further Ag atom neighbours are greater than 3.1 Å. NH₄Ag₂(AsS₂)₃ represents an ordered cyclo-thioarsenate(III) with three-membered As₃S₆ rings, (NH₄)₅Ag₁₆(AsS₄)₇ a neso-thioarsenate(V) with two split Ag atom positions. Both compounds were synthesized under moderate hydrothermal conditions.

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Synthesen und Kristallstrukturen von NH₄Ag₂(AsS₂)₃ und (NH₄)₅Ag₁₆(AsS₄)₇ mit einer Diskussion über (NH₄)S_x Polyeder

Zusammenfassung Die Atomanordnungen in den Strukturen von NH₄Ag₂(AsS₂)₃ [a=9.557(2),b=7.414(2),c=16.29(1) Å; =91.30(5)°; Raumgruppe P2₁/n;R(F)=0.042] und (NH₄)₅Ag₁₆(AsS₄)₇ [a=64.49(6),b=6.471(2),c=12.806(4) Å; =95.47(5)°; Raumgruppe Cc;R(F)=0.073] wurden anhand von röntgenographischen Einkristalldaten bestimmt. In diesen beiden Verbindungen sind die Koordinationsverhältnisse um die Ag-Atome sehr unterschiedlich. In NH₄Ag₂(AsS₂)₃ besitzen die Ag-Atome bis 3.3 Å eine [2+2]- und [3+1]-Koordination durch S-Atome mit weiteren Ag-Atomen bei 2.93 Å und 3.05 Å. In (NH₄)₅Ag₁₆(AsS₄)₇ sind die Ag-Atome mit einer Ausnahme [4]-koordiniert (Ag-S < 3.3 Å), und die Abstände zu weiteren Ag-Atomen sind größer als 3.1 Å. NH₄Ag₂(AsS₂)₃ stellt ein geordnetes Cyclothioarsenat(III) mit dreigliedrigen As₃S₆-Ringen dar, (NH₄)₅Ag₁₆(AsS₄)₇ ein Nesothioarsenat (V) mit zwei aufgespaltenen Ag-Positionen. Beide Verbindungen wurden unter mäßigen Hydrothermalbedingungen synthetisiert.

     

Comparison of the crystal structures of Co2(X 2O7)·2H2O,X=P and As

Summary Crystals of Co₂(X ₂O₇)·2H₂O,X=P/As were synthesized under hydrothermal conditions. Their crystal structures were determined by single crystal X-ray diffraction:a=6.334(1)/6.531(2),b=13.997(2)/14.206(4),c=7.637(1)/7.615(2)Å, =94.77(2)/94.74(2)°, space group P2₁/n,R=0.032/0.046,R _w=0.028/0.034 for 2423/2042 reflections and 131/119 variables. Within the twoXO₄ tetrahedra connected via a common corner to anX ₂O₇ group the average P-O bond lengths are approximately equal (1.540 and 1.543 Å), but As-O differs significantly (1.685 and 1.696 Å). A comparison with the isotypic Mn and Mg pyrophosphates shows a correlation between the ratio Me-O/X-O and the angle O-X-O.

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Vergleich der Kristallstrukturen von Co₂(X ₂O₇)·2H₂O,X=P und As

Zusammenfassung Kristalle von Co₂(X ₂O₇)·2H₂O,X=P/As wurden unter Hydrothermalbedingungen synthetisiert. Ihre Kristallstrukturen wurden mittels Röntgenbeugung an Einkristallen bestimmt:a=6.334(1)/6.531(2),b=13.997(2)/14.206(4),c=7.637(1)/7.615(2) Å, =94.77(2)/97.74(2)°, Raumgruppe P2₁/n,R=0.032/0.046,R _w=0.028/0.034 für 2423/2042 Reflexe und 131/119 Variable. In den beiden über eine gemeinsame Ecke zuX ₂O₇-Gruppen verknüpftenXO₄-Tetraedern sind die mittleren P-O-Abstände ungefähr gleich (1.540 und 1.543 Å), hingegen differiert As-O signifikant (1.685 und 1.696 Å). Ein Vergleich mit den isotypen Mn- und Mg-Pyrophosphaten zeigt eine Korrelation zwischen dem Quotienten Me-O/X-O und dem WinkelX-O-X.

     

Ein neuer Typ quaternärer Oxometallate: K3Na2[InO4]

With K₃Na₂[InO₄] the first example of new kind of oxides of the type A₃A₂[MO₄] with R(A)>R(A) was prepared in form of colourless single crystals by oxidation of the intermetallic compound KNaIn₂. Intimate mixtures of the educts (K₂O₂: K_0.5Na_0.5In=1.2:1) were heated in sealed Ag-tubes (380 °C, 2 d, then 480 °C, 5 d). K₃Na₂[InO₄] crystallizes monoclinic (P2₁/n) witha=1012.6 pm,b=969.9 pm,c=725.4 pm, =91.02°;Z=4. The crystal structure was elucidated by four-circle diffractometer (PW 1100, Ag-K, 6047I _o(hkl),R=7.3%,R _w=4.4%). The new typ forms a very complicated 3-dimensional network ³ {Na₂InO₄} stuffed by 3 K⁺. The Madelung part of lattice energy, MAPLE, is calculated and discussed.

Professor Edwin Hengge zum 60. Geburtstag am 21. Juli 1990 gewidmet     

Untersuchungen der Hydroxylammonium-Fluorozirconate(IV)

Summary Hydroxylammonium fluorozirconates have been investigated. Two new microcristalline phases have been isolated from aqueous solutions: (NH₃OH)₂ZrF₆ (1) and (NH₃OH)₃ZrF₇ (2). The crystals were prepared by slow evaporation of the solution of NH₂OH, Zr, and HF. Different compositions of the crystals were achieved by varying the molar ratios of the components. They were characterized by thermal analysis, vibrational spectroscopy, and structure (single crystal x-ray methods). (NH₃OH)₂ZrF₆ (1) crystallizes triclinic, P (No.: 2),a=7.400(2),b=7.609(2),c=7.887(2) Å, =57.29(3)°, =62.16(3)°, =67.83(2)°. (NH₃OH)₃ZrF₇ (2) crystallizes triclinic, P (No.: 2),a=7.128(1),b=7.989(1),c=8.888(1) Å, =109.72(1)°, =91.01(1)°, =104.27(1)°.

     

Crystal and molecular structure of a crown-bridgedp-t-butyl-calix[4]arene (1:1) pyridine complex. Host-guest interaction model based on molecular mechanics analysis [1]

The crystal and molecular structure of a crownedp-t-butyl-calix[4]arene (1:1) pyridine complex is reported. Colourless transparent prismatic crystals (obtained from pyridine) C₅₄H₇₄O₈·C₅H₅N,a=13.486(4),b=15.193(4),c=16.432(5) Å, =116.44(4)°, space groupP2₁,Z=2,D _calc=1.02g cm^–3, CuK radiation =1.5418 Å (CuK )=4.99 cm^–1. Refinement was carried out using 1702 reflections withI>3(I) toR 0.12. The macrocycle shows a distorted cone conformation which defines an intramolecular apolar cavity whose elliptical aperture is 11.5×8.6 Å calculated as distances between the two opposite central C atoms of the Bu ^t groups. A molecule of pyridine is included in this cavity, whereas the intermolecular cavities of the host lattice remain empty. The influence of the guest molecule on the conformation of the calixarene-crown is discussed. Potential energy calculations are performed in order to understand the nature of the host-guest interactions responsible for the stabilisation of the complex. Evidence for stabilizing CH₃- interactions are obtained from the calculations. Supplementary Data relevant to this article have been deposited with the British Library as supplementary Publication No. SUP 82068 (9 pages).