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1.  Rb2Lu[Si4O10]F, a tubular chain silicate 
Single crystals of Rb2Lu[Si4O10]F (dirubidium lutetium tetra­silicate fluoride) were obtained in flux-synthesis experiments in the system SiO2–Lu2O3–RbF. The compound belongs to the group of tubular chain silicates, i.e. it is based on multiple chains of condensed [SiO4] tetra­hedra forming closed columns. The periodicity of the unbranched multiple chains is four and corresponds to the length of the b axis. Adjacent columns are connected by Lu3+ cations, which are coordinated by four oxide and two fluoride anions in the form of slightly distorted octa­hedra. By sharing common fluoride corners, the single octa­hedra are linked into chains running parallel to the silicate tubes. Electroneutrality is achieved by the incorporation of additional Rb+ cations. All four symmetrically independent rubidium ions, four out of twelve oxide as well as the two fluoride anions are located on mirror planes. The remaining atoms reside on general positions.
doi:10.1107/S1600536814003043
PMCID: PMC3998444  PMID: 24764932
2.  The dehydrated copper silicate Na2[Cu2Si4O11]: a three-dimensional microporous framework with a linear Si—O—Si linkage 
The structure of the title dehydrated copper silicate, disodium dicopper undeca­oxide tetra­silicate, Na2(Cu2O11Si4), was determined by single-crystal X-ray diffraction from a non-merohedral twin. It exhibits an effective three-dimensional microporous framework with the major channels, in which the Na+ cations are placed, running along the a-axis direction and smaller channels observed along the b-axis direction. The structure is unusual in that it contains a symmetry-constrained Si—O—Si angle of 180°. The Cu centre is coordinated to five O atoms, exhibiting a slightly distorted square-pyramidal coordination geometry. The Na cation is interacting with five neighbouring O atoms, exhibiting an uncharacteristic coordination environment.
doi:10.1107/S1600536808001608
PMCID: PMC2960335  PMID: 21201246
3.  Poly[[tetra­aquatetrakis­[μ3-5-(pyridine-4-carboxamido)­isophthalato]cobalt(II)digadolinium(III)] tetra­hydrate] 
In the centrosymmetric polymeric title compound, {[CoGd2(C14H8N2O5)4(H2O)4]·4H2O}n, the GdIII cation is coordinated by one water mol­ecule and four pyridine-4-carboxamido­isophthalate (L) anions in a distorted square-anti­prismatic arrangement, while the CoII cation, located on an inversion center, is coordinated by two pyridyl-N atoms, two carboxyl­ate-O atoms and two water mol­ecules in a distorted octa­hedral geometry. The asymmetric unit contains two anionic L ligands: one bridges two Gd cations and one Co cation through two carboxyl groups and one pyridine-N atom; the other bridges two Gd cations and one Co cation through two carboxyl groups and the uncoordinated pyridine-N atom is hydrogen-bonded to the adjacent coordinated water mol­ecule. Extensive O—H⋯O and N—H⋯O hydrogen bonds are present in the crystal structure.
doi:10.1107/S1600536811038074
PMCID: PMC3201412  PMID: 22064912
4.  Crystal structures of Na2SeO4·1.5H2O and Na2SeO4·10H2O 
The crystal structures of the 1.5- and 10-hydrates of Na2SeO4 are isotypic with those of the corresponding chromates.
The crystal structures of Na2SeO4·1.5H2O (sodium selenate sesquihydrate) and Na2SeO4·10H2O (sodium selenate deca­hydrate) are isotypic with those of Na2CrO4·1.5H2O and Na2 XSeO4·10H2O (X = S, Cr), respectively. The asymmetric unit of the sesquihydrate contains two Na+ cations, one SeO4 tetra­hedron and one and a half water mol­ecules, the other half being generated by twofold rotation symmetry. The coordination polyhedra of the cations are a distorted monocapped octa­hedron and a square pyramid; these [NaOx] polyhedra are linked through common edges and corners into a three-dimensional framework structure, the voids of which are filled with the Se atoms of the SeO4 tetra­hedra. The structure is consolidated by O—H⋯O hydrogen bonds between coordinating water mol­ecules and framework O atoms. The asymmetric unit of the deca­hydrate consists of two Na+ cations, one SeO4 tetra­hedron and ten water mol­ecules. Both Na+ cations are octa­hedrally surrounded by water mol­ecules and by edge-sharing condensed into zigzag chains extending parallel to [001]. The SeO4 tetra­hedra and two uncoordinating water mol­ecules are situated between the chains and are connected to the chains through an intricate network of medium-strength O—H⋯O hydrogen bonds.
doi:10.1107/S1600536814011799
PMCID: PMC4158548  PMID: 25249853
isotypism; sodium selenate; salt hydrates; crystal structure
5.  A new mixed-valence lead(II) mangan­ese(II/III) phosphate(V): PbMnII 2MnIII(PO4)3  
The title compound, lead trimanganese tris(orthophosphate), has been synthesized by hydro­thermal methods. In this structure, only two O atoms are in general positions and all others atoms are in the special positions of the Imma space group. Indeed, the atoms in the Wyckoff positions are namely: Pb1 and P1 on 4e (mm2); Mn1 on 4b (2/m); Mn2 and P2 on 8g (2); O1 on 8h (m); O2 on 8i (m). The crystal structure can be viewed as a three-dimensional network of corner- and edge-sharing PO4 tetra­hedra and MnO6 octa­hedra, building two types of chains running along the b axis. The first is an infinite linear chain, formed by alternating MnIIIO6 octa­hedra and PO4 tetra­hedra which share one vertex. The second chain is built up from two adjacent edge-sharing octa­hedra (MnII 2O10 dimers) whose ends are linked to two PO4 tetra­hedra by a common edge. These chains are linked together by common vertices of polyhedra in such a way as to form porous layers parallel to (001). These sheets are bonded by the first linear chains, leading to the appearance of two types of tunnels, one propagating along the a axis and the other along b. The PbII ions are located within the inter­sections of the tunnels with eight neighbouring O atoms in form of a trigonal prism that is capped by two O atoms on one side. The three-dimensional framework of this structure is compared with similar phosphates such as Ag2Co3(HPO4)(PO4)2 and Ag2Ni3(HPO4)(PO4)2.
doi:10.1107/S1600536813016504
PMCID: PMC3772398  PMID: 24046541
6.  Poly[[tetra­aqua­(μ4-imidazole-4,5-dicarboxyl­ato)(μ3-imidazole-4,5-dicarboxyl­ato)-μ3-sulfato-μ2-sulfato-cobalt(II)digadolinium(III)] monohydrate] 
The asymmetric unit of the title compound, {[CoGd2(C5H2N2O4)2(SO4)2(H2O)4]·H2O}n, contains one CoII ion, two GdIII ions, two imidazole-4,5-dicarboxyl­ate ligands, two SO4 2− anions, four coordinated water mol­ecules and one uncoordinated water mol­ecule. The CoII ion is six-coordinated by two O atoms from two coordinated water mol­ecules, as well as two O atoms and two N atoms from two imidazole-4,5-dicarboxyl­ate ligands, giving a slightly distorted octa­hedral geometry. Both GdIII ions are eight-coordinated in a distorted bicapped trigonal–prismatic geometry. One GdIII ion is coordinated by four O atoms from two imidazole-4,5-dicarboxyl­ate ligands, three O atoms from three SO4 2− anions and a water O atom; the other GdIII ion is bonded to five O atoms from three imidazole-4,5-dicarboxyl­ate ligands, two O atoms from two SO4 2− anions as well as a water O atom. These metal coordination units are connected by bridging imidazole-4,5-dicarboxyl­ate and sulfate ligands, generating a heterometallic layer parallel to the ac plane. The layers are stacked along the b axis via N—H⋯O, O—H⋯O, and C—H⋯O hydrogen-bonding inter­actions, generating a three-dimensional framework.
doi:10.1107/S160053681104726X
PMCID: PMC3238650  PMID: 22199541
7.  BaMnII 2MnIII(PO4)3  
The title compound, barium trimanganese tris­(ortho­phosphate), was synthesized hydro­thermally. Its structure is isotypic with the lead and strontium analogues AMnII 2MnIII(PO4)3 (A = Pb, Sr). Except for two O atoms on general positions, all atoms are located on special positions. The Ba and one P atom exhibit mm2 symmetry, the MnII atom 2/m symmetry, the MnIII atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The crystal structure contains two types of chains running parallel to [010]. One chain is linear and is composed of alternating MnIIIO6 octa­hedra and PO4 tetra­hedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing MnIIO6 octa­hedra connected to PO4 tetra­hedra by edges and vertices. The two types of chains are linked through PO4 tetra­hedra into an open three-dimensional framework which contains channels parallel to [100] and [010] in which the BaII ions are located. The alkaline earth cation is surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.
doi:10.1107/S1600536813023106
PMCID: PMC3884417  PMID: 24426979
8.  Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O 
The crystal structures of the tri-, tetra- and nona­hydrate phases of Sr(ClO4)2 consist of Sr2+ ions coordinated by nine oxygen atoms from water mol­ecules and perchlorate tetra­hedra. O—H⋯O hydrogen bonds between water mol­ecules and ClO4 units lead to the formation of a three-dimensional network in each of the structures.
The title compounds, strontium perchlorate trihydrate {di-μ-aqua-aquadi-μ-perchlorato-strontium, [Sr(ClO4)2(H2O)3]n}, strontium perchlorate tetra­hydrate {di-μ-aqua-bis­(tri­aqua­diperchloratostrontium), [Sr2(ClO4)4(H2O)8]} and strontium perchlorate nona­hydrate {hepta­aqua­diperchloratostrontium dihydrate, [Sr(ClO4)2(H2O)7]·2H2O}, were crystallized at low temperatures according to the solid–liquid phase diagram. The structures of the tri- and tetra­hydrate consist of Sr2+ cations coordinated by five water mol­ecules and four O atoms of four perchlorate tetra­hedra in a distorted tricapped trigonal–prismatic coordination mode. The asymmetric unit of the trihydrate contains two formula units. Two [SrO9] polyhedra in the trihydrate are connected by sharing water mol­ecules and thus forming chains parallel to [100]. In the tetra­hydrate, dimers of two [SrO9] polyhedra connected by two sharing water mol­ecules are formed. The structure of the nona­hydrate contains one Sr2+ cation coordinated by seven water mol­ecules and by two O atoms of two perchlorate tetra­hedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water mol­ecules, which are located on twofold rotation axes. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ClO4 tetra­hedra and water mol­ecules as acceptor groups lead to the formation of a three-dimensional network in each of the three structures.
doi:10.1107/S1600536814024726
PMCID: PMC4257379  PMID: 25552979
crystal structure; low-temperature salt hydrates; perchlorate hydrates; strontium salts
9.  K9Y3[Si12O32]F2  
Single-crystals of the title compound, nona­potassium triyttrium dodeca­silicate difluoride, were obtained from flux synthesis experiments in the system SiO2—Y2O3—KF. The crystal structure belongs to the group of single-layer silicates and is based on silicate sheets parallel to (110). A single layer contains secondary (Q 2) and tertiary (Q 3) silicate tetra­hedra in the ratio 1:2 and is build up from six-, eight- and twelve-membered rings. The linkage between neighboring layers is achieved by two crystallographically independent Y3+ cations, which are coordinated by six oxygen ligands in form of distorted octa­hedra. Charge compensation is accomplished by incorporation of additional F− anions and K+ cations in the structural channels, forming anion-centred [F2K7] groups. Apart from one K+ and one Y3+ cation (each with site symmetry -1), the 30 crystallographically independent atoms reside on general positions.
doi:10.1107/S1600536814001470
PMCID: PMC3998244  PMID: 24764802
10.  Poly[μ-aqua-aqua-μ4-naphthalene-1,8-dicarboxyl­ato-barium]: a layer structure 
The title compound, [Ba(C12H6O4)(H2O)2]n, is represented by a layer-like structure built of BaO8 polyhedra. The asymmetric unit contains a Ba2+ ion, half a coordinating water mol­ecule and half a μ4-bridging naphthalene-1,8-dicarboxyl­ate (1,8-nap) ligand, the whole structure being generated by twofold rotational symmetry. The carboxyl­ate groups of the 1,8-nap ligands act as bridges linking four Ba2+ ions, while each Ba2+ ion is eight-coordinated by O atoms from four 1,8-nap ligands and two coordinating water mol­ecules. In the crystal, there are O—H⋯O hydrogen bonds involving the water mol­ecules and carboxyl­ate O atoms in the BaO8 polyhedra. Each BaO8 polyhedron is connected via corner-sharing water O atoms or edge-sharing ligand O atoms, forming a sheet parallel to the bc plane. These sheets stack along the a-axis direction and are connected via van der Waals forces only. The naphthalene groups protrude above and below the layers of the BaO8 polyhedra and there are voids of ca 208 Å3 bounded by these groups. No residual electron density was found in this region. The crystal studied was twinned by pseudo-merohedry, with a refined twin component ratio of 0.5261 (1):0.4739 (1).
doi:10.1107/S1600536813006259
PMCID: PMC3629495  PMID: 23634013
11.  SrMnII 2MnIII(PO4)3  
The title compound, strontium trimanganese tris­(ortho­phosphate), was synthesized under hydro­thermal conditions. Its structure is isotypic to that of the lead analogue PbMnII 2MnIII(PO4)3. Two O atoms are in general positions, whereas all others atoms are in special positions. The Sr and one P atom exhibit mm2 symmetry, the MnII atom 2/m symmetry, the MnIII atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The three-dimensional network of the crystal structure is made up of two types of chains running parallel to [010]. One chain is linear and is composed of alternating MnIIIO6 octa­hedra and PO4 tetra­hedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing MnIIO6 octa­hedra connected to PO4 tetra­hedra by edges and vertices. The two types of chains are linked through PO4 tetra­hedra, leading to the formation of channels parallel to [100] and [010] in which the SrII ions are located. They are surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.
doi:10.1107/S1600536813020977
PMCID: PMC3884376  PMID: 24426976
12.  MnBa2(HPO4)2(H2PO4)2  
Crystals of manganese(II) dibarium bis­(hydrogenphosphate) bis­(dihydrogenphosphate), MnBa2(HPO4)2(H2PO4)2, were obtained by hydro­thermal synthesis. The title compound is isotypic with its CdII and CaII analogues. The structure is built up of an infinite {[Mn(HPO4)2(H2PO4)2]4−}n chain running along [100], which consists of alternate MnO6 octa­hedra and [PO4] tetra­hedra, in which the centrosymmetric MnO6 octa­hedra share their four equatorial O-atom corners with tetra­hedral [PO3(OH)] groups and their two axial apices with tetra­hedral [PO2(OH)2] groups. These chains are held together by BaO9 coordination polyhedra, developing into a three-dimensional structure. The O—H⋯O hydrogen bonds additionally stabilize the structural set-up. Due to the ionic radius of Mn2+ being much smaller than those of Ca2+ and Cd2+, this may imply that their adopted structure type has a great tolerance for incorporating various ions and the exploitation of more diverse compounds in the future is encouraged.
doi:10.1107/S1600536812022775
PMCID: PMC3379057  PMID: 22719278
13.  Lithio­marsturite, LiCa2Mn2Si5O14(OH) 
Lithio­marsturite, ideally LiCa2Mn2Si5O14(OH), is a member of the pectolite–pyroxene series of pyroxenoids (hydro­pyroxenoids) and belongs to the rhodonite group. A previous structure determination of this mineral based on triclinic symmetry in space group P by Peacor et al. [Am. Mineral. (1990), 75, 409–414] converged with R = 0.18 without reporting any information on atomic coordinates and displacement param­eters. The current study redetermines its structure from a natural specimen from the type locality (Foote mine, North Carolina) based on single-crystal X-ray diffraction data. The crystal structure of lithio­marsturite is characterized by ribbons of edge-sharing CaO6 and two types of MnO6 octa­hedra as well as chains of corner-sharing SiO4 tetra­hedra, both extending along [110]. The octa­hedral ribbons are inter­connected by the rather irregular CaO8 and LiO6 polyhedra through sharing corners and edges, forming layers parallel to (1), which are linked together by the silicate chains. Whereas the coordination environments of the Mn and Li cations can be compared to those of the corresponding cations in nambulite, the bonding situations of the Ca cations are more similar to those in babingtonite. In contrast to the hydrogen-bonding scheme in babingtonite, which has one O atom as the hydrogen-bond donor and a second O atom as the hydrogen-bond acceptor, our study shows that the situation is reversed in lithio­marsturite for the same two O atoms, as a consequence of the differences in the bonding environments around O atoms in the two minerals.
doi:10.1107/S1600536811047581
PMCID: PMC3238580  PMID: 22199471
14.  Redetermination of the low-temperature polymorph of Li2MnSiO4 from single-crystal X-ray data 
Crystals of dilithium manganese(II) silicate were grown under high-temperature hydro­thermal conditions in the system LiOH—MnO2—SiO2. The title compound crystallizes in the βII-Li3PO4 structure type. The coordination polyhedra of all cations are slightly distorted tetra­hedra (m symmetry for MnO4 and SiO4), which are linked by corner-sharing to each other. The vertices of the tetra­hedra point to the same direction perpendicular to the distorted hexa­gonal close-packed (hcp) array of O atoms within which half of the tetra­hedral voids are occupied by cations. In comparison with the previous refinement from powder X-ray data [Dominko et al. (2006 ▶). Electrochem. Commun. 8, 217–222], the present reinvestigation from single-crystal X-ray data allows a more precise determination of the distribution of the Li+ and Mn2+ cations, giving a perfectly site-ordered structure model for both Li+ and Mn2+.
doi:10.1107/S1600536812035040
PMCID: PMC3435565  PMID: 22969438
15.  Apatite-type SrPr4(SiO4)3O 
Single crystals of the title compound, strontium tetra­praseo­dymium tris­(silicate) oxide, SrPr4(SiO4)3O, have been grown by the self-flux method using SrCl2. The structure is isotypic with the apatite supergroup family having the generic formula IX M12 VII M23(IV TO4)3 X, where M = alkaline earth and rare earth metals, T = Si and X = O. The M1 site (3.. symmetry) is occupied by Pr and Sr atoms with almost even proportions and is surrounded by nine O atoms forming a tricapped trigonal prism. The M2 site (m.. symmetry) is almost exclusively occupied by Pr and surrounded by seven O atoms, forming a distorted penta­gonal bipyramid. The Si atom (m.. symmetry) is surrounded by two O (m.. symmetry) and two O atoms in general positions, forming an isolated SiO4 tetra­hedron. Another O atom at the inversion centre (.. symmetry) is surrounded by three M2 sites, forming an equilateral triangle perpendicular to the c axis.
doi:10.1107/S1600536810033349
PMCID: PMC3008035  PMID: 21588475
16.  Nd2(WO4)3  
The title compound, dineodymium(III) tris­[tungstate(VI)], is a member of the Eu2(WO4)3 structure family and crystallizes isotypically with other rare earth tungstates and molybdates of this formula type. The structure is a derivative of the scheelite (CaWO4) structure and can be considered as an ordered defect variant with a threefold scheelite supercell and one rare earth (RE) site unoccupied. The Nd3+ cations are coordinated by eight O atoms in form of a distorted bicapped trigonal prism. The two unique W cations are tetra­hedrally surrounded by O atoms. One WO4 tetra­hedron has 2 symmetry and is relatively undistorted whereas the other tetra­hedron differs considerably from an ideal geometry. This is caused by an additional remote O atom at a distance of 2.149 (4) Å. The resulting WO4 + 1 polyhedra form W2O8 dimers through edge-sharing. Together with the WO4 and NdO8 units, the three-dimensional set-up is accomplished.
doi:10.1107/S1600536809018108
PMCID: PMC2969527  PMID: 21582980
17.  Disilver(I) trinickel(II) hydrogenphos­phate bis­(phosphate), Ag2Ni3(HPO4)(PO4)2  
The title compound, Ag2Ni3(HPO4)(PO4)2, has been synthesized by the hydro­thermal method. Its structure is formed by two types of chains running along the b axis. The first chain results from a linear and continuous succession of NiO6 octa­hedra linked to PO4 tetra­hedra by a common vertex. The second chain is built up from two adjacent edge-sharing octa­hedra (dimers) whose ends are linked to two PO4 tetra­hedra by a common edge. Those two types of chains are linked together by the phosphate groups to form polyhedral sheets parallel to the (001) plane. The three-dimensional framework delimits two types of hexa­gonal tunnels parallel to the a-axis direction, at (x, 1/2, 0) and (x, 0, 1/2), where the Ag atoms are located. Each silver cation is surrounded by eight O atoms. The same Ag+ coordination is found in other phosphates with the alluaudite structure, for example, AgMn3(PO4)(HPO4)2. Moreover, O—H⋯O hydrogen bonds link three PO4 tetra­hedra so as to build a three-dimensional network.
doi:10.1107/S1600536811021167
PMCID: PMC3151764  PMID: 21836825
18.  Trilithium thio­arsenate octa­hydrate 
The title compound, Li3AsS4·8H2O, is built up from infinite cationic [Li3(H2O)8]3+ chains which extend along [001] and are cross-linked by isolated tetra­hedral AsS4 3− anions via O—H⋯S hydrogen bonds. Two Li and two As atoms lie on special positions with site symmetries -1 (1 × Li) and 2 (1 × Li and 2 × As). The [Li3(H2O)8]3+ chain contains four independent Li atoms of which two are in octa­hedral and two in tetra­hedral coordination by water O atoms. An outstanding feature of this chain is a linear group of three edge-sharing LiO6 octa­hedra to both ends of which two LiO4 tetra­hedra are attached by face-sharing. Such groups of composition Li5O16 are linked into branched chains by means of a further LiO4 tetra­hedron sharing vertices with four adjacent LiO6 octa­hedra. The Li—O bonds range from 1.876 (5) to 2.054 (6) Å for the LiO4 tetra­hedra and from 2.026 (5) to 2.319 (5) Å for the LiO6 octa­hedra. The two independent AsS4 3− anions have As—S bond lengths ranging from 2.1482 (6) to 2.1677 (6) Å [ = 2.161 (10) Å]. The eight independent water mol­ecules of the structure donate 16 relatively straight O—H⋯S hydrogen bonds to all S atoms of the AsS4 tetra­hedra [ = 3.295 (92) Å]. Seven water mol­ecules are in distorted tetra­hedral coordination by two Li and two S; one water mol­ecule has a flat pyramidal coordination by one Li and two S. At variance with related compounds like Schlippe’s salt, Na3SbS4·9H2O, there are neither alkali–sulfur bonds nor O—H⋯O hydrogen bonds in the structure.
doi:10.1107/S1600536813010921
PMCID: PMC3647787  PMID: 23723753
19.  Crystal structure of the ternary silicide Gd2Re3Si5  
The crystal structure of this ternary silicide belongs to the U2Mn3Si5 structure type. The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo­octa­hedra and 13-vertex polyhedra, and the Si atoms are arranged as tricapped trigonal prisms, bicapped square anti­prisms, or 11-vertex polyhedra.
A single crystal of the title compound, the ternary silicide digadolinium trirhenium penta­silicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubo­octa­hedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square anti­prisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re—Re distance of 2.78163 (5) Å and isolated squares with an Re—Re distance of 2.9683 (6) Å.
doi:10.1107/S1600536814024234
PMCID: PMC4257405  PMID: 25552967
crystal structure; gadolinium; rhenium; silicon; inter­metallic compound; ternary silicide
20.  Crystal structures of Ca(ClO4)2·4H2O and Ca(ClO4)2·6H2O 
The crystal structures of the tetra- and hexa­hydrate phases of Ca(ClO4)2 consist of Ca2+ ions in distorted square-anti­prismatic environments and of perchlorate tetra­hedra. O—H⋯O hydrogen bonds between water mol­ecules and ClO4 units lead to the formation of a three-dimensional network in the structures.
The title compounds, calcium perchlorate tetra­hydrate and calcium perchlorate hexa­hydrate, were crystallized at low temperatures according to the solid–liquid phase diagram. The structure of the tetra­hydrate consists of one Ca2+ cation eightfold coordinated in a square-anti­prismatic fashion by four water mol­ecules and four O atoms of four perchlorate tetra­hedra, forming chains parallel to [01-1] by sharing corners of the ClO4 tetra­hedra. The structure of the hexa­hydrate contains two different Ca2+ cations, each coordinated by six water mol­ecules and two O atoms of two perchlorate tetra­hedra, forming [Ca(H2O)6(ClO4)]2 dimers by sharing two ClO4 tetra­hedra. The dimers are arranged in sheets parallel (001) and alternate with layers of non-coordinating ClO4 tetra­hedra. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ClO4 tetra­hedra and water mol­ecules as acceptor groups lead to the formation of a three-dimensional network in the two structures. Ca(ClO4)2·6H2O was refined as a two-component inversion twin, with an approximate twin component ratio of 1:1 in each of the two structures.
doi:10.1107/S1600536814024532
PMCID: PMC4257416  PMID: 25552974
crystal structure; low-temperature salt hydrates; perchlorate hydrates; calcium salts; Mars minerals
21.  Redetermination of Ba2CdTe3 from single-crystal X-ray data 
The previous structure determination of the title compound, dibarium tritelluridocadmate, was based on powder X-ray diffraction data [Wang & DiSalvo (1999 ▶). J. Solid State Chem. 148, 464–467]. In the current redetermination from single-crystal X-ray data, all atoms were refined with anisotropic displacement parameters. The previous structure report is generally confirmed, but with some differences in bond lengths. Ba2CdTe3 is isotypic with Ba2 MX 3 (M = Mn, Cd; X = S, Se) and features 1 ∞[CdTe2/2Te2/1]4− chains of corner-sharing CdTe4 tetra­hedra running parallel [010]. The two Ba2+ cations are located between the chains, both within distorted monocapped trigonal–prismatic coordination polyhedra. All atoms in the structure are located on a mirror plane.
doi:10.1107/S1600536812038974
PMCID: PMC3470123  PMID: 23125567
22.  Ba2Sb4GeS10  
The title quaternary compound, dibarium tetra­anti­mony germanium deca­sulfide, Ba2Sb4GeS10, crystallizes in a novel three-dimensional ∞ 3[Sb4GeS10]4− network structure, which is composed of triangular pyramidal SbS3 (site symmetry m..), distorted SbS5 (m..) polyhedra and regular GeS4 (-4..) tetra­hedra. The SbS3 and SbS5 units are connected with each other through corner- and edge-sharing, forming a Sb4S10 layer in the ab plane. The GeS4 tetra­hedra further bridge two neighbouring Sb4S10 layers, forming a three-dimensional ∞ 3[Sb4GeS10]4− network. The Ba2+ cation (..2) is located between two Sb4S10 layers and is coordinated by ten S atoms with Ba—S bond lengths in the range 3.2505 (9)–3.4121 (2) Å.
doi:10.1107/S1600536813007988
PMCID: PMC3647782  PMID: 23723748
23.  Poly[[diaqua­bis­(2,2′-bipyridine)­bis­(μ3-5-hy­droxy­isophthalato)(μ2-5-hy­droxy­isophthalato)digadolinium(III)] trihydrate] 
The asymmetric unit of the title coordination polymer, {[Gd2(C8H4O5)3(C10H8N2)2(H2O)2]·3H2O}n, contains two GdIII cations, one of which is surrounded by three 5-hy­droxy­isophthalate anions, one 2,2′-bipyridine ligand and two water mol­ecules in a distorted N2O7 tricapped trigonal–prismatic coordination geometry. The other Gd cation is coordinated by four 5-hy­droxy­isophthalate anions and one 2,2′-bipyridine ligand in a distorted N2O7 tricapped trigonal–prismatic coordination geometry. The 5-hy­droxy­isophthalate anions bridge the Gd cations, forming a layer structure. The layers are further connected by extensive O—H⋯O hydrogen bonding, assembling a three-dimensional supra­molecular network.
doi:10.1107/S1600536811035999
PMCID: PMC3201312  PMID: 22058695
24.  Dilead(II) trimanganese(II) bis(hydrogenphosphate) bis(phosphate) 
The title compound, Pb2Mn3(HPO4)2(PO4)2, was synthesized by a hydro­thermal method. All atoms are in general positions except for one Mn atom which is located on an inversion center. The framework of the structure is built up from PO4 tetra­hedra and two types of MnO6 octa­hedra, one almost ideal and the other very distorted with one very long Mn—O bond [2.610 (4) Å compared an average of 2.161 Å for the other bonds]. The centrosymetric octa­hedron is linked to two distorted MnO6 octa­hedra by an edge common, forming infinite zigzag Mn3O14 chains running along the b axis. Adjacent chains are linked by PO4 and PO3(OH) tetra­hedra through vertices or by edge sharing, forming sheets perpendicular to [100]. The Pb2+ cations are sandwiched between the layers and ensure the cohesion of the crystal structure. O—H⋯O hydrogen bonding between the layers is also observed.
doi:10.1107/S1600536812033259
PMCID: PMC3414095  PMID: 22904702
25.  Poly[di-μ-aqua-di­aqua­bis­(μ7-oxalato-κ9 O 1:O 1:O 1,O 2:O 2:O 2′:O 2′,O 1′:O 1′)calciumdicaesium] 
In the title compound, [CaCs2(C2O4)2(H2O)4]n, the Ca2+ ion, lying on a twofold rotation axis, is coordinated by four O atoms from two oxalate ligands and two bridging water mol­ecules in an octa­hedral geometry. The Cs+ ion is coordinated by seven O atoms from six oxalate ligands, one bridging water and one terminal water mol­ecule. The oxalate ligand displays a scarce high denticity. The structure contains parallel chain units runnig along [10-1], formed by two edge-sharing Cs polyhedra connected by CsO9 polyhedra connected by a face-sharing CaO6 octahedron. These chains are further linked by the oxalate ligands to build up a three-dimensional framework. O—H⋯O hydrogen bonds involving the water mol­ecules and the carboxyl­ate O atoms enhance the extended structure.
doi:10.1107/S1600536813022654
PMCID: PMC3884383  PMID: 24426991

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