Ba[Co3(VO4)2(OH)2] with a regular Kagomé lattice

The new layered title compound, barium di‐μ‐hydroxido‐di‐μ‐vanadato‐tricobaltate(II), was prepared under low‐temperature hydrothermal conditions. Its crystal structure comprises Co²⁺ and O²⁻ ions in the Kagomé geometry. The octahedral Co₃O₆(OH)₂ Kagomé layers, made up of edge‐shared CoO₄(OH)₂ octahedra with Co on a site of 2/m symmetry, alternate along the c axis with barium vanadate heteropolyhedral layers, in which Ba is on a site of m symmetry and V is on a site of 3m symmetry. All three O atoms and the H atom also occupy special positions: two O atoms and the H atom are on sites with 3m symmetry and one O atom is on a site with m symmetry. Ba[Co₃(VO₄)₂(OH)₂] represents the first compound from the four‐component BaO–CoO–V₂O₅–H₂O system and its structure is topologically related to the minerals vesignieite, Ba[Cu₃(VO₄)₂(OH)₂], and bayldonite, Pb[Cu₃(AsO₄)₂(OH)₂].     

Crystal Chemistry of the M11+,2+–M22+,3+–(H)‐Arsenites: the First Cadmium(II) Arsenite,Na4Cd7(AsO3)6

The crystal structures among M1–M2–(H)‐arsenites (M1 = Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cd²⁺, Pb²⁺; M2 = Mg²⁺, Mn^2+,3+, Fe^2+,3+, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) are less investigated. Up to now, only the structure of Pb₃Mn(AsO₃)₂(AsO₂OH) was described. The crystal structure of hydrothermally synthesized Na₄Cd₇(AsO₃)₆ was solved from the single‐crystal X‐ray diffraction data. Its trigonal crystal structure [space group R$\bar{3}$ , a = 9.5229(13), c = 19.258(4) Å, γ = 120°, V = 1512.5(5) ų, Z = 3] represents a new structure type. The As atoms are arranged in monomeric (AsO₃)^3– units. The surroundings of the two crystallographically unique sodium atoms show trigonal antiprismatic coordination, and two mixed Cd/Na sites are remarkably unequal showing tetrahedral and octahedral coordinations. Despite the 3D connection of the AsO₃ pyramids, (Cd,Na)O_x polyhedra and NaO₆ antiprisms, a layer‐like arrangement of the Na atoms positioned in the hexagonal channels formed by CdO₄ deformed tetrahedra and AsO₃ pyramids in z = 0, 1/3, 2/3 is to be mentioned. These pseudo layers are interconnected to the 3D network by (Cd,Na)O₆ octahedra. Raman spectra confirmed the presence of isolated AsO₃ pyramids.     

A spin‐frustrated cobalt(II) carbonate pyrochlore network

The crystal structure of the cobalt(II) carbonate‐based compound cobalt(II) dicarbonate trisodium chloride, Co(CO₃)₂Na₃Cl, grown from a water–ethanol mixture, exhibits a three‐dimensional network of corner‐sharing {Co₄(μ₃‐CO₃)₄} tetrahedral building blocks, in which the Co^II centres define a pyrochlore lattice and reside in a slightly distorted octahedral Co(O–CO₂)₆ environment. The space outside the hexagonal framework defined by these interlinked groups is occupied by Na⁺ and Cl⁻ ions. Antiferromagnetic coupling between adjacent Co^II centres, mediated by carbonate bridges, results in geometric spin frustration which is typical for pyrochlore networks. The Co and Cl atoms reside on the special position , one Na atom on position 2 and a carbonate C atom on position 3.     

Na1.72Mn3.28(AsO4)3

The single crystal of sodium manganese arsenate (1.72/3.28/12), Na_1.72Mn_3.28(AsO₄)₃, used for analysis was prepared by solid‐state reaction at 1073 K. The compound crystallizes in the monoclinic system in space group C2/c. The structure consists of a complex network of edge‐sharing MnO₆ octahedral chains, linked together by AsO₄ tetrahedra, forming two distinct channels, one containing Na⁺ cations and the other occupied statistically by Mn⁺ and Na⁺ cations.     

Cobalt(II) and cobalt(III) complexes with 4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine

4′‐Cyanophenyl‐2,2′:6′,2′′‐terpyridine (cptpy) was employed as an N,N′,N′′‐tridentate ligand to synthesize the compounds bis[4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine]cobalt(II) bis(tetrafluoridoborate) nitromethane solvate, [Co^II(C₂₂H₁₄N₄)₂](BF₄)₂·CH₃NO₂, (I), and bis[4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine]cobalt(III) tris(tetrafluoridoborate) nitromethane sesquisolvate, [Co^III(C₂₂H₁₄N₄)₂](BF₄)₃·1.5CH₃NO₂, (II). In both complexes, the cobalt ions occupy a distorted octahedral geometry with two cptpy ligands in a meridional configuration. A greater distortion from octahedral geometry is observed in (I), which indicates a different steric consequence of the constrained ligand bite on the Co^II and Co^III ions. The crystal structure of (I) features an interlocked sheet motif, which differs from the one‐dimensional chain packing style present in (II). The lower dimensionality in (II) can be explained by the disturbance caused by the larger number of anions and solvent molecules involved in the crystal structure of (II). All atoms in (I) are on general positions, and the F atoms of one BF₄⁻ anion are disordered. In (II), one B atom is on an inversion center, necessitating disorder of the four attached F atoms, another B atom is on a twofold axis with ordered F atoms, and the C and N atoms of one nitromethane solvent molecule are on a twofold axis, causing disorder of the methyl H atoms. This relatively uncommon study of analogous Co^II and Co^III complexes provides a better understanding of the effects of different oxidation states on coordination geometry and crystal packing.     

Hydrothermal Synthesis,Crystal Structure Determination,and Magnetic Properties of a New Calcium Iron Iridium Hydrogarnet Ca3(Ir2–xFex)(FeO4)2–x(O4H4)1+x with 0 ≤ x ≤ 1

The new calcium iron iridium hydrogarnet Ca₃(Ir_2–xFe_x)(FeO₄)_2–x(H₄O₄)_1+x (0 ≤ x ≤ 1) was obtained by hydrothermal synthesis under strongly oxidizing alkaline conditions. The compound adopts a garnet‐like crystal structure and crystallizes in the acentric cubic space group I4 3d (no. 220) with a = 12.5396(6) Å determined at T = 100 K for a crystal with a refined composition Ca₃(Ir_1.4Fe_0.6)(FeO₄)_1.4(O₄H₄)_1.6. Iridium and iron statistically occupy the octahedrally coordinated metal position, the two crystallographically independent tetrahedral sites are partially occupied by iron. Hydroxide groups are found to cluster as hydrogarnet defects, i.e. partially substituting oxide anions around the empty tetrahedral metal sites. The presence of hydroxide ions was confirmed by infrared spectroscopy and the hydrogen content was quantified by carrier gas hot extraction; the overall composition was verified by energy dispersive X‐ray spectroscopy. The structure model is supported by ⁵⁷Fe‐Mössbauer spectroscopic data evidencing different Fe sites and a magnetic ordering of the octahedral iron sublattice at room temperature. The thermal decomposition proceeds via three steps of water loss and results in Ca₂Fe₂O₅, Fe₂O₃ and Ir. Mössbauer and magnetization data suggest magnetic order at ambient temperature with complex magnetic interactions.     

Diaquabis(4‐fluorobenzoato‐κO)bis(nicotinamide‐κN)cobalt(II)

The title compound, [Co(C₇H₄FO₂)₂(C₆H₆N₂O)₂(H₂O)₂], is a three‐dimensional hydrogen‐bonded supramolecular complex. The Co^II ion resides on a centre of symmetry and is in an octahedral coordination environment comprising two pyridyl N atoms, two carboxylate O atoms and two O atoms from water molecules. Intermolecular N—H...O and O—H...O hydrogen bonds produce R₃²(6), R₂²(12) and R₂²(16) rings, which lead to two‐dimensional chains. An extensive three‐dimensional network of C—H...F, N—H...O and O—H...O hydrogen bonds and π–π interactions are responsible for crystal stabilization.     

Sodium scandium arsenate,Na3Sc2(AsO4)3

Nasicon-type trisodium discandium tris­(arsenate), Na₃Sc₂(AsO₄)₃, contains a polyhedral network of vertex-sharing octahedral ScO₆ and tetrahedral AsO₄ units [d_av(Sc—O) = 2.089 (2) Å and d_av(As—O) = 1.672 (2) Å] encapsulating two types of Na⁺ species. The sodium site occupancies are similar to those of the equivalent species in β-Na₃Sc₂(PO₄)₃.     

CsGa(H1.5AsO4)2(H2AsO4) and isotypic CsCr(H1.5AsO4)2(H2AsO4): decorated kröhnkite‐like chains in two unusual hydrogen arsenates

Hydro­thermally synthesized caesium gallium(III) hydrogen arsenate(V), CsGa(H_1.5AsO₄)₂(H₂AsO₄), (I), and isotypic caesium chromium(III) hydrogen arsenate(V), CsCr(H_1.5AsO₄)₂(H₂AsO₄), (II), represent a new structure type and stoichiometry among M^I–M^III hydrogen arsenates. The crystal structure, determined from single‐crystal X‐ray diffraction data, is based on an infinite octa­hedral–tetra­hedral chain and can be described as a decorated kröhnkite‐like chain. The chains extend parallel to [100] and are separated by ten‐coordinated Cs atoms. The hydrogen‐bonding scheme comprises one very short symmetry‐restricted hydrogen bond, with O⋯O distances of 2.519 (4) and 2.508 (4) Å in (I) and (II), respectively, and two further medium–strong hydrogen bonds, all of which reinforce the connections between adjacent chains. The average Ga—O and Cr—O bond lengths are 1.973 (15) and 1.980 (13) Å, respectively, and the average As—O bond lengths in the two protonated arsenate groups lie within a very narrow range [1.690 (18)–1.69 (3) Å]. The Cs atom is located on a centre of inversion, while the M^III and As2 atoms lie on twofold axes. Relationships to CaBa₂(HPO₄)₂(H₂PO₄)₂ and other compounds containing decorated kröhnkite‐type or kröhnkite‐like chains are discussed.     

Li12Cu16+xAl26−x (x = 3.2): a new intermetallic structure type

The new ternary lithium copper aluminide, Li₁₂Cu_16+xAl_26−x (x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/m.. site and one Cu atom occupies a general site. The framework of Li₁₂Cu_16+xAl_26−x consists of pseudo‐Frank–Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl₂ and Li₈Cu_12+xAl_6−x) and to the well known CaCu₅ structure.     

Poly[[trans‐diaquabis(μ2‐biphenyl‐2,2′‐dicarboxylato)bis(μ2‐4,4′‐bipyridine)dicobalt(II)] biphenyl‐2,2′‐dicarboxylic acid disolvate]

In the title compound, {[Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂(H₂O)₂]·2C₁₄H₁₀O₄}_n, each Co^II ion is six‐coordinate in a slightly distorted octahedral geometry. Both Co^II ions are located on twofold axes. One is surrounded by two O atoms from two biphenyl‐2,2′‐dicarboxylate (dpa) dianions, two N atoms from two 4,4′‐bipyridine (bpy) ligands and two water molecules, while the second is surrounded by four O atoms from two dpa dianions and two N atoms from two bpy ligands. The coordinated dpa dianion functions as a κ³‐bridge between the two Co^II ions. One carboxylate group of a dpa dianion bridges two adjacent Co^II ions, and one O atom of the other carboxylate group also chelates to a Co^II ion. The Co^II ions are bridged by dpa dianions and bpy ligands to form a chiral sheet. There are several strong intermolecular hydrogen bonds between the H₂dpa solvent molecule and the chiral sheet, which result in a sandwich structure.     

Cobalt(II) and Cobalt(III) Tri‐tert‐butoxysilanethiolates. Synthesis,Properties, Crystal and Molecular Structures of [Co{μ‐SSi(OBut)3}{SSi(OBut)3}(NH3)]2 and [Co{SSi(OBut)3}2(NH3)4][SSi(OBut)3] Complexes

The heteroleptic neutral tri‐tert‐butoxysilanethiolate of cobalt(II) incorporating ammonia as additional ligand ( 1 ) has been prepared by the reaction of a cobalt(II) ammine complex with tri‐tert‐butoxysilanethiol in water. Complex 1 , dissolved in hexane, undergoes oxidation in an ammonia saturated atmosphere to the ionic cobalt(III) compound 2 . Molecular and crystal structures of 1 and 2 have been determined by single crystal X‐ray structural analysis. 1 forms a dimeric molecule [Co{μ‐SSi(OBu^t)₃}{SSi(OBu^t)₃}(NH₃)]₂ with a folded central Co₂S₂ ring and distorted tetrahedral ligand arrangement at both Co^II atoms (CoNS₃ core). The product 2 is composed of the octahedral Co^III complex cation [Co{SSi(OBu^t)₃}₂(NH₃)₄]⁺ and the tri‐tert‐butoxysilanethiolate anion. Within the crystal two pairs of ions interact by hydrogen bonds forming well separated entities. 1 and 2 are the first structurally characterized cobalt thiolates where metal is also bonded to ammonia and 2 is the first cobalt(III) silanethiolate.     

An arsenate with the α‐CrPO4 structure type,NaCa1–xNi3–2xAl2x(AsO4)3 (x = 0.23): crystal structure,charge‐distribution and bond‐valence‐sum analyses

Since the discovery of electrochemically active LiFePO₄, materials with tunnel and layered structures built up of transition metals and polyanions have become the subject of much research. A new quaternary arsenate, sodium calcium trinickel aluminium triarsenate, NaCa_1–x Ni_3–2x Al_2x (AsO₄)₃ (x = 0.23), was synthesized using the flux method in air at 1023 K and its crystal structure was determined from single‐crystal X‐ray diffraction (XRD) data. This material was also characterized by qualitative energy‐dispersive X‐ray spectroscopy (EDS) analysis and IR spectroscopy. The crystal structure belongs to the α‐CrPO₄ type with the space group Imma . The structure is described as a three‐dimensional framework built up of corner‐edge‐sharing NiO₆, (Ni,Al)O₆ and AsO₄ polyhedra, with channels running along the [100] and [010] directions, in which the sodium and calcium cations are located. The proposed structural model has been validated by bond‐valence‐sum (BVS) and charge‐distribution (CHARDI) tools. The sodium ionic conduction pathways in the anionic framework were investigated by means of the bond‐valence site energy (BVSE) model, which predicted that the studied material will probably be a very poor Na⁺ ion conductor (bond‐valence activation energy ∼7 eV).     

A polymeric cobalt(II) complex derived from citric acid (H4cit) and 2,6‐diaminopurine (dap): {[Co4(cit)2(dap)4(H2O)4]·6.35H2O}n

Poly[[tetraaquadi‐μ₄‐citrato‐tetrakis(2,6‐diaminopurine)tetracobalt(II)] 6.35‐hydrate], {[Co₄(C₆H₄O₇)₂(C₅H₆N₆)₄(H₂O)₄]·6.35H₂O}_n, presents three different types of Co^II cations in the asymmetric unit, two of them lying on symmetry elements (one on an inversion centre and the other on a twofold axis). The main fragment is further composed of one fully deprotonated citrate (cit) tetraanion, two 2,6‐diaminopurine (dap) molecules and two aqua ligands. The structure is completed by a mixture of fully occupied and disordered solvent water molecules. The two independent dap ligands are neutral and the cit tetraanion provides for charge balance, compensating the 4+ cationic charge. There are two well defined coordination geometries in the structure. The simplest is mononuclear, with the Co^II cation arranged in a regular centrosymmetric octahedral array, coordinated by two aqua ligands, two dap ligands and two O atoms from the β‐carboxylate groups of the bridging cit tetraanions. The second, more complex, group is trinuclear, bisected by a twofold axis, with the metal centres coordinated by two cit tetraanions through their α‐ and β‐carboxylate and α‐hydroxy groups, and by two dap ligands bridging through one of their pyridine and one of their imidazole N atoms. The resulting coordination geometry around each metal centre is distorted octahedral. Both groups are linked alternately to each other, defining parallel chains along [201], laterally interleaved and well connected via hydrogen bonding to form a strongly coupled three‐dimensional network. The compound presents a novel μ₄‐κ⁵O:O,O′:O′,O′′,O′′′:O′′′′ mode of coordination of the cit tetraanion.     

Nd5(AsO3)4Cl3: The First Oxo‐Arsenate(III)‐Chloride of the Lanthanides

Single crystals of Nd₅(AsO₃)₄Cl₃ (monoclinic, P2/n, Z = 2, a = 1026.0(1), b = 543.35(3), c = 1400.2(1) pm, β = 93.48(1)°) were obtained from the reaction of Nd₂O₃, As₂O₃ and NaCl in a sealed silica ampoule. In the crystal structure the Nd³⁺ ions are linked by AsO₃^3? groups into layers that alternate with layers of Cl^? ions. Two of the three crystallographically different Nd³⁺ ions are coordinated by eight oxygen atoms, the third one has four oxygen and four chlorine atoms as neighbours.     

(μ‐C‐meso‐5,5,7,12,12,14‐Hexa­methyl‐1,4,8,11‐tetra­aza­cyclo­tetra­decane‐N‐acetato‐1κ5N,N′,N′′,N′′′,O:2κO′)­tetra­chloro‐1κCl,2κ3Cl‐cobalt(III)­zinc(II)

The crystal structure of the title compound, [CoCl(C₁₈H₃₇N₄O₂){ZnCl₃}], has been determined by X‐ray diffraction.C‐meso‐5,5,7,12,12,14‐Hexa­methyl‐1,4,8,11‐tetra­aza­cyclotetradecane‐N‐acetate acts as a bridging ligand to coodinate with Co^III and Zn^II ions. The Co^III ion is six‐coordinate in a nearly octahedral environment provided by one Cl atom, four N atoms of the bridging ligand, and one O atom. The Zn^II ion is four‐coordinate in a distorted tetrahedral environment completed by three Cl atoms and an O atom of the bridging ligand.     

Lithium and sodium yttrium ortho­silicate oxy­apatite,LiY9(SiO4)6O2 and NaY9(SiO4)6O2, at both 100 K and near room temperature

Lithium yttrium orthosilicate oxyapatite [lithium nonayttrium hexakis­(silicate) dioxide], LiY₉(SiO₄)₆O₂, crystallizes in the centrosymmetric space group P6₃/m at both 295 and 100 K. The structure closely resembles those of fluorine apatite and sodium yttrium orthosilicate oxyapatite [sodium nonayttrium hexakis­(silicate) dioxide], NaY₉(SiO₄)₆O₂, which was also investigated, at 270 and 100 K, in this study. There are two different crystallographic sites for the Y³⁺ ion, which are coordinated by seven and nine O atoms. One‐fourth of the nine‐coordinated site is occupied by Li or Na atoms, thus maintaining charge balance. The Si atom occupies a tetrahedral site. The two compounds show no symmetry change between room temperature and 100 K, and the alterations in structural parameters are small.     

Hexa­aqua­nickel(II) bis­(hypophosphite)

The structure of hexa­aqua­nickel(II) bis­(hypophosphite), [Ni(H₂O)₆](H₂PO₂)₂, has been determined. The crystals are prismatic. The packing of the Ni and P atoms (not the entire hypophosphite anions) is the same as in the structures of [Co(H₂O)₆](H₂PO₂)₂ and [Co_0.5Ni_0.5(H₂O)₆](H₂PO₂)₂. The Ni^II cations have a pseudo‐face‐centered cubic cell, with cell parameter a 10.216 Å and tetrahedral cavities occupied by P atoms. The Ni^II cation has crystallographically imposed twofold symmetry and has an octahedral coordination sphere consisting of six water O atoms, two of which also lie on the twofold axis. The planes of oppositely coordinated water mol­ecules are in a cross conformation. The geometry of the hypophosphite anion is close to point symmetry mm2. The hypophosphite anions are hydrogen bonded to the coordinated water molecules.     

Synthese und Struktur eines Hochtemperatur-Cobaltarsenats(V): H?Co3(AsO4)2

Synthesis and Structure of a High Temperature Cobaltarsenate: H? Co₃(AsO₄)₂ Single crystals of the high temperature compound H? Co₃(AsO₄)₄ were prepared at 1800°C with a CO₂-Laser technique. X-ray single crystal work shows monoclinic symmetry (space group C-P2₁/c; a = 6.457, b = 8.510, c = 11.187 Å; ß = 90.73°). In opposition to monoclinic m-CO₃(AsO₄)₂ H? Co₃(AsO₄)₂ has a different coordination of Co²⁺ including a different connection of the distorted polyhedra. There exists a significant similarity to Cu₃(AsO₄)₂.     

Nanocrystals of Co2+‐Doped MgGa2O4: Preparation by a Low‐Temperature Combustion Method and Optical Properties

Co²⁺‐doped MgGa₂O₄ nanocrystals were prepared at 500°C by a low‐temperature combustion method without any further calcination. Powder X‐ray diffraction (XRD) indicated that the only crystalline phase in the product was MgGa₂O₄ with a grain size of 33–36 nm. Scanning electron microscopy (SEM) showed that the products contained pores formed by the gases evolved during the combustion reaction. The excitation and emission spectra of the nanocrystalline powders in the visible and near infrared regions were characteristic of tetrahedral Co²⁺ ions, suggesting that Co²⁺ ions replaced tetrahedral Mg²⁺ ions in the MgGa₂O₄ crystals. We assigned the visible and near infrared luminescent bands to the spin‐allowed ⁴T₁(⁴P) → and ⁴A₂(⁴F) and ⁴T₁(⁴P) → ⁴T₂(⁴F) transitions.