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1.  Tetra­kis(dihydrogen pefloxacinium) di-μ2-chlorido-bis­[tetra­chloridobismuthate(III)] tetra­chloride octa­hydrate 
The title compound {systematic name: tetra­kis[4-(3-carb­oxy-1-ethyl-6-fluoro-4-hydroxonio-1,4-dihydro-7-quinol­yl)-1-meth­yl­piperazin-1-ium] di-μ2-chlorido-bis­[tetra­chlorido­bismuth­ate(III)] tetra­chloride octa­hydrate}, (C17H22FN3O3)4[Bi2Cl10]Cl4·8H2O, is composed of edge-shared centrosymmetric dinuclear [Bi2Cl10]4− anions, Cl− anions, dihydrogen pefloxacinium cations and water mol­ecules. The BiIII coordination polyhedron is a distorted octa­hedron. There are four short terminal Bi—Cl bonds [2.5037 (10)–2.6911 (7) Å] and two longer bridging bonds [2.8834 (8) and 3.0687 (9) Å] in each octa­hedron. Two sets of chloride ions and water mol­ecules are disordered over the same sites with site occupancies of 1/3 and 2/3, respectively. Anions, cations and water mol­ecules are linked by O—H⋯O, O—H⋯Cl and N—H⋯Cl hydrogen bonds, forming a three-dimensional framework. There are also π–π stacking inter­actions between quinoline ring systems [centroid–centroid distance = 3.575 (1) Å].
PMCID: PMC2961801  PMID: 21202786
2.  Tricaesium tris­(pyridine-2,6-dicarboxyl­ato-κ3 O 2,N,O 6)lutetium(III) octa­hydrate 
Colourless block crystals of the title compound, Cs3[Lu(dipic)3]·8H2O [dipic is dipicolinate or pyridine-2,6-dicarboxyl­ate, C7H3NO4] were synthesized by slow evaporation of the solvent. The crystal structure of this LuIII-complex, isostructural with the DyIII and EuIII complexes, was determined from a crystal twinned by inversion and consists of discrete [Lu(dipic)3]3− anions, Cs+ cations and water mol­ecules involving hydrogen bonding. The Lu atom lies on a twofold rotation axis and is coordinated by six O atoms and three N atoms of three dipicolinate ligands. One Cs atom is also on a twofold axis. The unit cell can be regarded as successive layers along the crystallographic c-axis formed by [Lu(dipic)3]3− anionic planes and [Cs+, H2O] cationic planes. In the crystal structure, although the H atoms attached to water mol­ecules could not be located, short O—O contacts clearly indicate the occurrence of an intricate hydrogen-bonded network through contacts with other water mol­ecules, Cs cations or with the O atoms of the dipicolinate ligands.
PMCID: PMC2959249  PMID: 21201028
3.  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.
PMCID: PMC3647787  PMID: 23723753
4.  Calcium disodium hexa­thio­diphosphate(IV) octa­hydrate 
Single crystals of the title compound, CaNa2(P2S6)·8H2O, were obtained by adding calcium hydroxide to an aqueous solution of Na4(P2S6)·6H2O. The structure is isotypic with that of its strontium analogue and consists of one Ca2+ cation, two Na+ cations, one-half of a centrosymmetric (P2S6)4− anion with staggered confirmation and four water mol­ecules in the asymmetric unit. The crystal structure can be described as being built up from layers of cations and anions extending parallel to (101). Within a layer, each CaO8 polyhedron is connected via edge-sharing to two NaO4S2 octa­hedra and to one NaO2S4 octa­edron. The NaO4S2 octa­hedra are, in turn, linked with two (P2S6)4− anions through common corners. Various O—H⋯S hydrogen-bonding inter­actions lead to cohesion of adjacent layers. The Ca2+ and one Na+ cation are situated on a twofold rotation axis and the second Na+ cation is situated on an inversion centre.
PMCID: PMC3007360  PMID: 21588077
5.  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.
PMCID: PMC3884417  PMID: 24426979
6.  Hexaaqua­nickel(II) tetra­aqua­bis­(μ-pyridine-2,6-dicarboxyl­ato)bis­(pyridine-2,6-dicarboxyl­ato)trinickelate(II) octa­hydrate 
The title compound, [Ni(H2O)6][Ni3(C7H3NO4)4(H2O)4]·8H2O, was obtained by the reaction of nickel(II) nitrate hexa­hydrate with pyridine-2,6-dicarb­oxy­lic acid (pydcH2) and 1,10-phenanothroline (phen) in an aqueous solution. The latter ligand is not involved in formation of the title complex. There are three different NiII atoms in the asymmetric unit, two of which are located on inversion centers, and thus the [Ni(H2O)6]2+ cation and the trinuclear {[Ni(pydc)2]2-μ-Ni(H2O)4}2− anion are centrosymmetric. All NiII atoms exhibit an octa­hedral coordination geometry. Various inter­actions, including numerous O—H⋯O and C—H⋯O hydrogen bonds and C—O⋯π stacking of the pyridine and carboxyl­ate groups [3.570 (1), 3.758 (1) and 3.609 (1) Å], are observed in the crystal structure.
PMCID: PMC3007465  PMID: 21588093
7.  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.
PMCID: PMC4158548  PMID: 25249853
isotypism; sodium selenate; salt hydrates; crystal structure
8.  Crystal structure of [Y6(μ6-O)(μ3-OH)8(H2O)24]I8·8H2O 
In the crystal structure of a hexa­nuclear Y3+ compound, the six Y3+ cations are arranged octa­hedrally around an μ6-O atom at the centre of the cationic complex. Each of the eight faces of the Y6 octa­hedron is capped by an μ3-OH group in the form of a distorted cube. The proximity of the cationic complexes and lattice water mol­ecules leads to the formation of a three-dimensional hydrogen-bonded network of medium strength.
The crystal structure of the title compound {systematic name: octa-μ3-hydroxido-μ6-oxido-hexa­kis­[tetra­aqua­yttrium(III)] octa­iodide octa­hydrate}, is characterized by the presence of the centrosymmetric mol­ecular entity [Y6(μ6-O)(μ3-OH)8(H2O)24]8+, in which the six Y3+ cations are arranged octa­hedrally around a μ6-O atom at the centre of the cationic complex. Each of the eight faces of the Y6 octa­hedron is capped by an μ3-OH group in the form of a distorted cube. In the hexa­nuclear entity, the Y3+ cations are coordinated by the central μ6-O atom, the O atoms of four μ3-OH and of four water mol­ecules. The resulting coordination sphere of the metal ions is a capped square-anti­prism. The crystal packing is quite similar to that of the ortho­rhom­bic [Ln 6(μ6-O)(μ3-OH)8(H2O)24]I8·8H2O structures with Ln = La—Nd, Eu—Tb, Dy, except that the title compound exhibits a slight monoclinic distortion. The proximity of the cationic complexes and the lattice water mol­ecules leads to the formation of a three-dimensional hydrogen-bonded network of medium strength.
PMCID: PMC4257455  PMID: 25552996
crystal structure; hexa­nuclear compounds; lanthanide compound; three-dimensional hydrogen-bonded network
9.  Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O 
The crystal structures of ZnCl2·xH2O (x = 2.5, 3 and 4.5) consist of Zn2+ ions both in an octa­hedral and tetra­hedral environment. O—H⋯O hydrogen bonds between water mol­ecules and tetra­hedral ZnCl4 units lead to the formation of a three-dimensional network in each of the structures.
The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl− and H2O around Zn2+. According to the solid–liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn2+ both in a tetra­hedral coordination with Cl− and in an octa­hedral environment defined by five water mol­ecules and one Cl− shared with the [ZnCl4]2− unit. Thus, these two different types of Zn2+ cations form isolated units with composition [Zn2Cl4(H2O)5] (penta­aqua-μ-chlorido-tri­chlorido­di­zinc). The trihydrate {hexa­aqua­zinc tetra­chlorido­zinc, [Zn(H2O)6][ZnCl4]}, consists of three different Zn2+ cations, one of which is tetra­hedrally coordinated by four Cl− anions. The two other Zn2+ cations are each located on an inversion centre and are octa­hedrally surrounded by water mol­ecules. The [ZnCl4] tetra­hedra and [Zn(H2O)6] octa­hedra are arranged in alternating rows parallel to [001]. The structure of the 4.5-hydrate {hexa­aqua­zinc tetra­chlorido­zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa­hedral [Zn(H2O)6] and tetra­hedral [ZnCl4] units, as well as additional lattice water mol­ecules. O—H⋯O hydrogen bonds between the water mol­ecules as donor and ZnCl4 tetra­hedra and water mol­ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures.
PMCID: PMC4257420  PMID: 25552980
crystal structure; low-temperature salt hydrates; chloride hydrates; zinc salts
10.  Redetermination of [EuCl2(H2O)6]Cl 
The crystal structure of the title compound, hexa­aqua­dichlorido­europium(III) chloride, was redetermined with modern crystallographic methods. In comparison with the previous study [Lepert et al. (1983 ▶). Aust. J. Chem. 36, 477–482], it could be shown that the atomic coordinates of some O atoms had been confused and now were corrected. Moreover, it was possible to freely refine the positions of the H atoms and thus to improve the accurracy of the crystal structure. [EuCl2(H2O)6]Cl crystallizes with the GdCl3·6H2O structure-type, exhibiting discrete [EuCl2(H2O)6]+ cations as the main building blocks. The main blocks are linked with isolated chloride anions via O—H⋯Cl hydrogen bonds into a three-dimensional framework. The Eu3+ cation is located on a twofold rotation axis and is coordinated in the form of a Cl2O6 square anti­prism. One chloride anion coordinates directly to Eu3+, whereas the other chloride anion, situated on a twofold rotation axis, is hydrogen bonded to six octa­hedrally arranged water mol­ecules.
PMCID: PMC4051107  PMID: 24940187
11.  μ-Oxido-bis­[bis­(phenanthroline-κ2 N,N′)(sulfato-κO)iron(III)] octa­hydrate 
The title complex, [Fe2O(SO4)2(C12H8N2)4]·8H2O, contains two unique FeIII cations, one oxide anion, four 1,10-phenanthroline (phen) ligands, two coordinated sulfate anions and eight lattice water mol­ecules. Each FeIII ion has an approximate octa­hedral geometry, coordinated by four N atoms from two phen mol­ecules, two O atoms from oxide and sulfate anions, respectively. The parallel phen mol­ecules form two-dimensional supermolecules through π–π stacking inter­actions [centroid–centroid distances = 3.684 (3), 3.711 (3), 3.790 (3), 3.847 (3), 3.746 (3), 3.732 (3) and 3.729 (3) Å]. This architecture is further stabilized by O—H⋯O hydrogen bonds involving the lattice water mol­ecules and sulfate O atoms.
PMCID: PMC3246986  PMID: 22219806
12.  Co3(PO4)2·4H2O 
Single crystals of Co3(PO4)2·4H2O, tricobalt(II) bis­[ortho­phosphate(V)] tetra­hydrate, were obtained under hydro­thermal conditions. The title compound is isotypic with its zinc analogue Zn3(PO4)2·4H2O (mineral name hopeite) and contains two independent Co2+ cations. One Co2+ cation exhibits a slightly distorted tetra­hedral coordination, while the second, located on a mirror plane, has a distorted octa­hedral coordination environment. The tetra­hedrally coordinated Co2+ is bonded to four O atoms of four PO4 3− anions, whereas the six-coordinate Co2+ is cis-bonded to two phosphate groups and to four O atoms of four water mol­ecules (two of which are located on mirror planes), forming a framework structure. In addition, hydrogen bonds of the type O—H⋯O are present throughout the crystal structure.
PMCID: PMC2959263  PMID: 21200978
13.  Ammonium 4,4-difluoro-1,3,2-dithia­zetin-2-ide 1,1,3,3-tetra­oxide 
The asymmetric unit of the title compound, NH4 +·CF2NO4S2 −, consists of two crystallographically independent ammonium cations and two 4,4-difluoro-1,3,2-dithia­zetin-2-ide 1,1,3,3-tetra­oxide anions all located in general positions. The S—C—S—N rings of both crystallographically independent anions are almost planar, with the N atom bent out of the plane by 9.82 (5) and 12.82 (4)°. The structure was determined from a crystal twinned by inversion, with refined components in the ratio 0.73 (4):0.27 (4). Anions and cations are connected via hydrogen bonds (N—H⋯O and N—H⋯N) to form a three-dimensional framework. This framework is composed of two different layers parallel to the ab plane, which are built by the ammonium cations on the one hand and the complex cyclic anions on the other.
PMCID: PMC3393267  PMID: 22807824
14.  Lutetium ultraphosphate 
The structure of the title compound, LuP5O14, comprises puckered eight-membered PO4 rings linked by the lutetium cations in a complex way, forming a three-dimensional framework. Each eight-membered phosphate ring shares a bridging tetra­hedron with each of four adjacent tetra­hedra, to form layers of PO4 tetra­hedra. These layers are c/2 in thickness and parallel to the ab plane. Each Lu ion is contained in one such layer, forming bonds to six O atoms in that layer and also to one O atom belonging to a tetra­hedron in each of the layers lying above and below it. The LuO8 polyhedra are isolated from one another, since they share no common atoms. The Lu ions lie on twofold axes (special position 4e) and the shortest Lu⋯Lu distance is 5.703 (1) Å.
PMCID: PMC2961625  PMID: 21202435
15.  Redetermination of K4[Bi2Cl10]·4H2O 
In comparison with the previous refinement of tetra­potassium di-μ-chlorido-bis­[tetra­chloridobismuthate(III)] tetra­hydrate [Volkova, Udovenko, Levin & Shevchenko (1983). Koord. Khim. 9, 356–360], the current redetermination reveals anisotropic displacement parameters for all non-H atoms, localization of the H atoms, and higher precision of lattice parameters and inter­atomic distances. The crystal structure is built up of edge-sharing [Bi2Cl10]4− double octa­hedra with the bridging Cl atoms situated on a mirror plane, three K+ counter-cations (two of which are on mirror planes), and two water mol­ecules that are solely coordinated to the K+ cations. These building units are linked into a three-dimensional network structure. Additional O—H⋯Cl hydrogen bonds between the water mol­ecules and the complex anions stabilize this arrangement.
PMCID: PMC2960101  PMID: 21581105
16.  Di­chlorido­(5,10,15,20-tetra­phenyl­porphyrinato-κ4 N)anti­mony(V) hexa­chlorido­anti­monate(V) 
The asymmetric unit of the title compound, [Sb(C44H28N4)Cl2][SbCl6], consists of one half of an anti­mony(V) tetra­phenyl­porphyrin complex cation and one half of an hexa­chlorido­anti­monate(V) anion. In the complex cation, the SbV atom lies on an inversion center and is octa­hedrally coordinated by four N atoms from a macrocyclic tetra­phenyl­porphyrinate ligand and two chloride ions. The complex cation has approximately a planar core with a maximum deviation of 0.018 (5) Å from the porphyrin mean plane. The average Sb—N distance is 2.062 (11) Å, while the Sb—Cl distance is 2.355 (1) Å. The SbV atom of the anion is also located on an inversion center. The [SbCl6]− octa­hedron exhibits rhombic distortion characterized by the Sb—Cl bond lengths [2.311 (3), 2.374 (2) and 2.393 (4) Å]. In the crystal, the cations and anions are linked C—H⋯ Cl hydrogen bonds, forming a layer parallel to (211).
PMCID: PMC4120531  PMID: 25161522
17.  Bis[8-ethyl-5-oxo-2-(piperazin-4-ium-1-yl)-5,8-dihydro­pyrido[2,3-d]pyrimidine-6-carb­oxy­lic acid] 2,5-dicarb­oxy­benzene-1,4-di­carboxyl­ate octa­hydrate 
The asymmetric unit of the title compound, 2C14H18N5O3 +·C10H5O8 2−·8H2O, contains one [H2ppa]+cation, one half of an [H2btec]2− anion (H4btec = 1,2,4,5-benzene­tetra­carb­oxy­lic acid and Hppa = 8-ethyl-5-oxo-2-piperazin-1-yl-5,8-dihydro­pyrido[2,3-d]pyrimidine-6-carb­oxy­lic acid) that is completed by inversion symmetry and four water mol­ecules. In the crystal, the mol­ecules are connected by inter­molecular hydrogen-bonding inter­actions and π–π stacking between the benzene rings of the [H2btec]2− anion and the pyrimidine rings of the [H2ppa]+ cation [centroid–centroid distance = 3.597 (3) Å], generating a three-dimensional supra­molecular structure.
PMCID: PMC3099930  PMID: 21754029
18.  catena-Poly[bis­(4-amino­pyridinium) [[diaqua­manganese(II)]-di-μ-chlorido] dichloride] 
Single crystals of the title organic–inorganic hybrid, {(C5H7N2)2[MnCl2(H2O)2]Cl2}n, were synthesized from an ethanol solution containing manganese(II) chloride tetra­hydrate and 4-amino­pyridine under acidic conditions. The asymmetric unit contains a disordered organic cation (occupancies in the ratio 0.72:0.28), a chloride anion and an MnCl(H2O) moiety with the MnII atom located on an inversion center. The structure is built up of infinite chains of edge-sharing [MnCl4(H2O)2] octa­hedra developing parallel to the a axis which are separated by the 4-amino­pyridinium ions and discrete chloride ions. The organic cations occupy the empty space around each inorganic chain. Structural cohesion is organized through N—H⋯Cl and O—H⋯Cl hydrogen bonds, which build up a three-dimensional network.
PMCID: PMC2977461  PMID: 21583377
19.  Crystal structure of trans-di­fluoridotetra­kis(pyridine-κN)chromium(III) tri­chlorido­(pyridine-κN)zincate monohydrate from synchrotron data 
The CrIII atoms in the title compound show a distorted octa­hedral coordination with four pyridine N atoms in the equatorial plane and two F atoms in axial positions. The [ZnCl3(C5H5N)]− anion has a distorted tetra­hedral geometry.
In the asymmetric unit of the title compound, [CrF2(C5H5N)4][ZnCl3(C5H5N)]·H2O, there are two independent complex cations, one tri­chlorido­(pyridine-κN)zincate anion and one solvent water mol­ecule. The cations lie on inversion centers. The CrIII ions are coordinated by four pyridine (py) N atoms in the equatorial plane and two F atoms in a trans axial arrangement, displaying a slightly distorted octa­hedral geometry. The Cr—N(py) bond lengths are in the range 2.0873 (14) to 2.0926 (17) Å while the Cr—F bond lengths are 1.8609 (10) and 1.8645 (10) Å. The [ZnCl3(C5H5N)]− anion has a distorted tetra­hedral geometry. The Cl atoms of the anion were refined as disordered over two sets of sites in a 0.631 (9):0.369 (9) ratio. In the crystal, two anions and two water mol­ecules are linked via O—H⋯Cl hydrogen bonds, forming centrosymmetric aggregates. In addition, weak C—H⋯Cl, C—H⋯π and π–π stacking inter­actions [centroid–centroid distances = 3.712 (2) and 3.780 (2)Å] link the components of the structure into a three-dimensional network.
PMCID: PMC4257241  PMID: 25484725
crystal structure; fluoride ligand; pyridine ligand; trans-isomer; chromium(III) complex
20.  Poly[[μ-(1-ammonio­ethane-1,1-di­yl)bis­(hydrogenphospho­nato)]diaquachloridodisodium]: a powder X-ray diffraction study 
The title compound, [Na2(C2H8NO6P2)Cl(H2O)2]n, has a polymeric two-dimensional structure extending parallel to (001). The asymmetric unit contains two Na+ cations located on a centre of symmetry and on a mirror plane, respectively, one half of a bis-phospho­nate anion (the entire anion is completed by mirror symmetry), one chloride anion on a mirror plane and one water mol­ecule in general positions. The two Na+ cations exhibit distorted octa­hedral NaCl2O4 coordination polyhedra, each consisting of two deprotonated O atoms of the bis-phospho­nate anion, of two water mol­ecules and of two chloride anions. Strong O—H⋯O hydrogen bonds between the –OH group and one of the free O atoms of the bis-phospho­nate anion connect adjacent layers along [100], supported by N—H⋯Cl inter­actions. Intra­layer O—H⋯O and N—H⋯O hydrogen bonds are also observed.
PMCID: PMC3344415  PMID: 22590177
21.  Bis(tetra­phenyl­arsonium) di-μ-hy­droxido-bis­[(nitrilo­triacetato)­cobalt(III)] octa­hydrate 
In the title compound, (C24H20As)2[Co2(C6H6NO6)2(OH)2]·8H2O, the CoIII atom in the binuclear centrosymmetric anion is octa­hedrally surrounded by one N atom and three O atoms of the tetra­dentate nitrilo­triacetate ligand and two μ-hydroxide ligands. The crystal packing is controlled by C—H⋯O and O—H⋯O hydrogen-bonding inter­actions. The crystal employed in this study proved to be a two-component twin around (01).
PMCID: PMC3009231  PMID: 21588834
22.  Poly[[octaaqua-μ4-(benzene-1,2,4,5-tetra­carboxyl­ato)-dicobalt(II)] octa­hydrate] 
The title polymeric coordination compound, {[Co2(C10H2O8)(H2O)8]·8H2O}n, was obtained by slow diffusion of a dilute aqueous solution of CoCl2 and the sodium salt of benzene-1,2,4,5-tetracarboxylic acid (H4btec) through an agar–agar gel bridge in a U-shaped tube. The two independent Co2+ ions are each situated on an inversion centre and are coordinated in a slightly distorted octa­hedral geometry by four water O atoms and two carboxyl­ate O atoms from two btec4− ligands (-1> symmetry), forming a layer parallel to (11-1). This layer can be described as a mol­ecular two-dimensional square grid with the benzene rings at the nodes and the CoII atoms connecting the nodes. O—H⋯O hydrogen-bonding interactions involving the coordinating water molecules, the carboxylate O atoms and lattice water molecules lead to the formation of a three-dimensional network.
PMCID: PMC3885008  PMID: 24454183
23.  Strontium disodium hexa­thio­diphosphate(IV) octa­hydrate 
The crystal structure of SrNa2(P2S6)·8H2O is isotypic with that of its calcium analogue. The asymmetric unit consists of one Sr2+ cation (2 symmetry), two Na+ cations (2 and symmetry, respectively), one-half of a centrosymmetric (P2S6)4− anion with a staggered confirmation and four water mol­ecules. The crystal structure is built up from layers of cations and anions extending parallel to (101). Each SrO8 polyhedron is connected via edge-sharing to two NaO4S2 octa­hedra and to one NaO2S4 octa­hedron. The NaO4S2 octa­edra are, in turn, connected with two (P2S6)4− anions through common corners. Adjacent layers are held together by several O—H⋯S hydrogen-bonding inter­actions.
PMCID: PMC3007201  PMID: 21588078
24.  Poly[(μ3-hydrogenphosphato)(4H-1,2,4-triazole-κN 1)zinc] 
The asymmetric unit of the title compound, [Zn(HPO4)(C2H3N3)]n, contains one Zn2+ cation, one (HPO4)2− anion and a 1,2,4 triazole ligand. The Zn2+ cation is coordinated in a quite regular tetra­hedral geometry by O atoms from three phosphate groups and a tertiary N atom from the triazole ring. Each phosphate anion is connected to three ZnII cations, leading to a series of corrugated organic–inorganic layers parallel to the ac plane. The overall structure involves stacking of complex hybrid organic–inorganic layers along the b axis. Cohesion in the crystal is ensured by an infinite three-dimensional network of N—H⋯O and O—H⋯O hydrogen bonds between the phosphate groups and the triazole ligands.
PMCID: PMC3515161  PMID: 23284388
25.  catena-Poly[[di­aqua­bis­(4-formyl­benzoato-κO 1)copper(II)]-μ-pyrazine-κ2 N:N′] 
In the title polymeric compound, [Cu(C8H5O3)2(C4H4N2)(H2O)2]n, the CuII atom is located on a twofold rotation axis and has a slightly distorted octa­hedral coordination sphere. In the equatorial plane, it is coordinated by two carboxyl­ate O atoms of two symmetry-related monodentate formyl­benzoate anions and by two N atoms of the bridging pyrazine ligand, which is bis­ected by the twofold rotation axis. The axial positions are occupied by two O atoms of the coordinating water mol­ecules. In the formyl­benzoate anion, the carboxyl­ate group is twisted away from the attached benzene ring by 6.2 (2)°, while the benzene and pyrazine rings are oriented at a dihedral angle of 68.91 (8)°. The pyrazine ligands bridge the CuII cations, forming polymeric chains running along the b-axis direction. Strong intra­molecular O—H⋯O hydrogen bonds link the water mol­ecules to the carboxyl­ate O atoms. In the crystal, O—Hwater⋯Owater hydrogen bonds link adjacent chains into layers parallel to the bc plane. The layers are linked via C—Hpyrazine⋯Oform­yl hydrogen bonds, forming a three-dimensional network. There are also weak C—H⋯π inter­actions present.
PMCID: PMC3914040  PMID: 24526956

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