| 1. |
- Casari, Barbara M., et al.
(author)
-
A pseudo-merohedrally twinned rare-earth sulfate: K6[Ce(HSO4)2(SO4)4]·H2O, a novel structure type
- 2007
-
In: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; C63:4, s. i25-i27
-
Journal article (peer-reviewed)abstract
- A novel structure type of an acidic rare-earth sulfate, hexapotassium cerium dihydrogensulfate tetrasulfate monohydrate, is reported. The crystal is twinned, mimicking tetragonal symmetry. The CeIV atom is nine-coordinate, connecting to one corner-sharing and four edge-sharing sulfate groups. One of the potassium ions is disordered over two general positions. The compound is unique as it contains rare-earth monomers, [Ce(HSO4)(SO4)4]5-. The structure is composed of these monomers, water molecules, discrete hydrogensulfate ions and potassium ions held together by ionic interactions. There are two types of alternating layers in the structure, with compositions [K4Ce(HSO4)(SO4)4]- and [K2(HSO4)(H2O)]+.
|
|
| 2. |
- Casari, Barbara M., et al.
(author)
-
Dipotassium tetrachromate(VI), K2Cr4O13
- 2005
-
In: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; C61:12, s. i117-i119
-
Journal article (peer-reviewed)abstract
- The structure of dipotassium tetrachromium(VI) tridecaoxide, K2Cr4O13, has been determined from single-crystal X-ray data collected at 173(2)K on a racemically twinned crystal with monoclinic Pc space-group symmetry. The structure is composed of discrete [Cr4O13]2- zigzag chains held together by the charge-balancing potassium ions. The conformations adopted by the tetrachromate anion in alkali metal salts and Cr8O21 are different and can be divided into three categories.
|
|
| 3. |
- Casari, Barbara M., et al.
(author)
-
New Aquapentachlorochromate(III) Compounds: K2[CrCl5(H2O)] and (NH4)2[CrCl5(H2O)]
- 2006
-
In: Zeitschrift für Anorganische und Allgemeine Chemie. - 0044-2313 .- 1521-3749. ; 632:1, s. 101-106
-
Journal article (peer-reviewed)abstract
- Synthesis and crystal structures of two new compounds, K2[CrCl5(H2O)] (I) and (NH4)2[CrCl5(H2O)] (II) are reported. Both compounds were prepared from chromium(VI) salts by two different methods and reaction pathways of these syntheses are suggested. The crystal structures of these two aquapentachlorochromates(III) have been determined from three dimensional X-ray data collected at low temperature, 173 K. The two structures are isomorphous and their unit cell dimensions are quite similar. They are orthorhombic, space groups Pnma, with Z = 4. Both structures are composed of [CrCl5(H2O)]2- units held together by the counterion framework. The coordination around the chromium ion deviates from a regular octahedron due to the shorter equatorial chromium-oxygen bond.
|
|
| 4. |
- Casari, Barbara M., et al.
(author)
-
New Open-Framework Mixed-Valence Chromium(III) Cerium(III)/(IV) Sulfate: CrCeIII7CeIV6(HSO4)6(SO4)21·75H2O
- 2007
-
In: European Journal of Inorganic Chemistry. ; 2007:22, s. 3514-3518
-
Journal article (peer-reviewed)abstract
- The title compound, synthesized from CrVI and CeIV species, crystallizes in the space group P63 with a = 19.3015(2), c = 25.2684(4) Å, and Z = 2. The structural design of the title compound differs essentially from structures of known mixed-valence cerium compounds which all form three-dimensional networks. In the title compound the cerium atoms, interlinked by sulfate groups, extend to form layers held together by hydrogen-bonding contacts. Perpendicular to these layers there are 10 Å wide channels. One third of the channels host solvent water only, while the other two thirds of the channels also host [Cr(H2O)6]3+ and [Ce(SO4)3(H2O)6]3- units, blocking each of these channels once per unit cell, resulting in 14 Å long voids.
|
|
| 5. |
- Casari, Barbara M., et al.
(author)
-
New Structure Type among Octahydrated Rare-Earth Sulfates, β-Ce2(SO4)3·8H2O, and a new Ce2(SO4)3·4H2O Polymorph
- 2007
-
In: Zeitschrift für Anorganische und Allgemeine Chemie. - : Wiley. - 0044-2313 .- 1521-3749. ; 633:7, s. 1074-1081
-
Journal article (peer-reviewed)abstract
- Syntheses, crystal structures and thermal behavior of two new hydrated cerium(III) sulfates are reported, Ce2(SO4)3·4H2O (I) and β-Ce2(SO4)3·8H2O (II), both forming three-dimensional networks. Compound I crystallizes in the space group P21/n. There are two non-equivalent cerium atoms in the structure of I, one nine- and one ten-fold coordinated to oxygen atoms. The cerium polyhedra are edge sharing, forming helically propagating chains, held together by sulfate groups. The structure is compact, all the sulfate groups are edge-sharing with cerium polyhedra and one third of the oxygen atoms, belonging to sulfate groups, are in the S-Oμ3-Ce2 bonding mode. Compound II constitutes a new structure type among the octahydrated rare-earth sulfates which belongs to the space group Pn. Each cerium atom is in contact with nine oxygen atoms, these belong to four water molecules, three corner sharing and one edge sharing sulfate groups. The crystal structure is built up by layers of [Ce(H2O)4(SO4)]nn+ held together by doubly edge sharing sulfate groups. The dehydration of II is a three step process, forming Ce2(SO4)3·5H2O, Ce2(SO4)3·4H2O and Ce2(SO4)3, respectively. During the oxidative decomposition of the anhydrous form, Ce2(SO4)3, into the final product CeO2, small amount of CeO(SO4) as an intermediate species was detected.
|
|
| 6. |
- Casari, Barbara M., et al.
(author)
-
Syntheses and Crystal Structures of Hydrated Ternary Cerium Sulfates: Mixed-valence K5Ce2(SO4)6·H2O and K2Ce(SO4)3·H2O
- 2007
-
In: Zeitschrift für Anorganische und Allgemeine Chemie. - : Wiley. - 0044-2313 .- 1521-3749. ; 633:7, s. 1055-1061
-
Journal article (peer-reviewed)abstract
- A new chemical and structural interpretation of K5Ce2(SO4)6·H2O (I) and a redetermination of the structure of K2Ce(SO4)3·H2O (II) is presented. The mixed-valent compound I crystallizes in the space group C2/c with a = 17.7321(3), b = 7.0599(1), c = 19.4628(4) Å, beta = 112.373(1)° and Z = 4. Compound I has been discussed earlier with space group Cc. In the structure of I, there are pairs of edge sharing cerium polyhedra connected by sulfate oxygen atoms in the 3 bonding mode. These cerium dimers are linked through edge and corner sharing sulfate bridges, forming layers. The layers are joined by potassium ions which together with the water molecules are placed between the layers. No irregularity in the distribution of the CeIII and CeIV to cause the lost of a crystallographic center of symmetry was detected. We suggest that the charge exerted by the extra f1 electron for every cerium dimer is delocalized over the Ce1-O2-Ce2 moiety in a non-bonding mode. As a result, the oxidations state of each cerium ion is a mean value between III and IV at each atomic position. Compound II crystallizes in the space group C2 with a = 20.6149(2), b = 7.0742(1), c = 17.8570(1) Å, beta = 122.720(1)° and Z = 8. The hydrogen atoms have been located and the absolute structure has been established. Neither hydrogen atom positions nor anisotropic displacement parameters were given in the previous reports. In compound II, the cerium polyhedra are connected by edge and corner sharing sulfate groups forming a three-dimensional network. This network contains Z-shaped channels hosting the charge compensating potassium ions.
|
|
| 7. |
- Casari, Barbara M., et al.
(author)
-
Synthesis Methods for Ce(CrO4)2 · xH2O and Crystal Structures of K2CrSO7, (NH4)2Cr2O7 and Na2Cr2O7 · 2H2O
- 2007
-
In: Zeitschrift für Naturforschung - Section B Journal of Chemical Sciences. - 0932-0776. ; 62b:6, s. 771-777
-
Journal article (peer-reviewed)abstract
- New and quick methods to synthesize Ce(CrO4)2 · 2H2O and Ce(CrO4)2 · H2O, giving high yields,are described. The methods are based on exchange reactions by refluxing in water or on solid statereactions. The first crystal structure containing a chromatosulfato ion is presented. K2CrSO7 belongsto space group P21/n with a=7.4024(1), b=7.3908(1), c=12.9883(2) Å , β=90.021(1)◦ and Z = 4.The CrSO72− ion, consisting of one chromate group sharing one oxygen atom with one sulfate group, has a pseudo syn-C2v conformation with eclipsed oxygen atoms. K2CrSO7 forms a three dimensional network of CrSO72− ions held together by the charge balancing potassium ions, with the generalstructural features common with dichromate-like structures. The redetermination of the structures of(NH4)2Cr2O7 (space group C2/c, with hydrogen atoms located) and Na2Cr2O7 · 2H2O (space group P21, with hydrogen atoms located and the absolute structure established) are reported.
|
|
| 8. |
- Casari, Barbara M., et al.
(author)
-
The orthorhombic polymorph of diammonium trichromate(VI) decaoxide, α-(NH4)2Cr3O10
- 2007
-
In: Journal of Chemical Crystallography. - : Springer Science and Business Media LLC. - 1074-1542 .- 1572-8854. ; 37:2, s. 135-140
-
Journal article (peer-reviewed)abstract
- Synthesis and crystal structure of a trichromium(VI) decaoxide compound, α-(NH4)2Cr3O10, is reported. The crystal structure has been determined from three dimensional X-ray data collected at low temperature, 173 K. The structure is isomorphous with its Rb and Cs trichromate analogues, orthorhombic, space group Pbca, with a = 11.2558(3), b = 9.3193(3), c = 18.9819(5) Å and Z = 8. The title compound is composed of discrete [Cr3O10]2- chains held together by the counter ion charge and a hydrogen bonding network. The different conformations adopted by trichromate anion within its ammonium, alkali and organic salts are discussed.
|
|
| 9. |
- Casari, Barbara M., et al.
(author)
-
Two Ce(SO4)2·4H2O polymorphs: Crystal structure and thermal behavior
- 2007
-
In: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 180:5, s. 1616-1622
-
Journal article (peer-reviewed)abstract
- Syntheses, crystal structures and thermal behavior of two polymorphic forms of Ce(SO4)2·4H2O are reported. The first modification, α-Ce(SO4)2·4H2O (I), crystallizes in the orthorhombic space group Fddd, with a=5.6587(1), b=12.0469(2), c=26.7201(3) Å and Z=8. The second modification, β-Ce(SO4)2·4H2O (II), crystallizes in the orthorhombic space group Pnma, with a=14.6019(2), b=11.0546(2), c=5.6340(1) Å and Z=4. In both structures, the cerium atoms have eight ligands: four water molecules and four sulfate groups. The mutual position of the ligands differs in (I) and (II), resulting in geometrical isomerism. Both these structures are built up by layers of Ce(H2O)4(SO4)2 held together by a hydrogen bonding network. The dehydration of Ce(SO4)2·4H2O is a two step (I) and one step (II) process, respectively, forming Ce(SO4)2 in both cases. During the decomposition of the anhydrous form, Ce(SO4)2, into the final product CeO2, intermediate xCeO2·yCe(SO4)2 species are formed.
|
|
| 10. |
- Eriksson, Annika, 1975, et al.
(author)
-
Pentapotassium sodium hexasulfatodicerate(III)
- 2003
-
In: Acta Crystallographica Section E: Structure Reports Online. - 1600-5368. ; E59:11, s. i149-i150
-
Journal article (peer-reviewed)abstract
- K5Na[Ce2(SO4)6] contains two CeIII ions, cross-linked via two oxygen and four sulfate bridges, a unique configuration for cerium sulfates. Each cerium is (8 + 2)-coordinated by O atoms of four sulfate groups by bidentate linkages.
|
|
