Reactions of [Co(NH3)6]Cl3 and K3[Co(C2O4)3] in aqueous solutions result in formation of a new double complex salt, [Co(NH3)6][Co(C2O4)3] (1). The crystal structure of 1 is triclinic [space group , a = 7.5180 (5) Å, b = 9.4283 (5) Å, c = 11.4968 (7) Å, α = 84.018 (4), β = 87.508(4), γ = 71.254(4)°] and is derived from a CsCl archetype. It is analogous to the previously reported [Ir(NH3)6][Co(C2O4)3] and [Co(NH3)6][Ir(C2O4)3], which are also triclinic and crystallize in the space group . The difference in the number of water molecules in comparison with the previously studied [Co(NH₃)₆][Co(C₂O₄)₃]·3H2O (sp. gr. P ) can be explained by different methods for obtaining single crystals suitable for X-ray diffraction analysis. These findings expand the data pool on double complex salts with cations and anions based on the same transition metal cation, and underline the effect of incorporated water molecules on the crystal structure.

Abstract A new organically templated hybrid organo-inorganic compound, (C 4 H 12 N 2 )SO 4 ⋅3H 2 SeO 3 , was prepared during systematic studies of sulfate co-crystals with selenious acid. The new compound crystallizes in a non-centrosymmetric space group P 2 1 ( a = 6.2876(2) Å, b = 17.9296(6) Å, c = 7.2701(3) Å, β = 106.979(4)°, R 1 = 0.027) and exhibits a weak SHG activity. The new compound belongs to a rapidly developing family of hydrogen-bonded architectures formed by selenious acid co-crystals. The crystal structure corresponds to a pseudo-layered hydrogen-bonded framework with alternating organic and inorganic “slabs” linked by hydrogen bonds.

Crystals of two new alkaline-earth perrhenate halides, Sr(ReO4)Br⋅2H2O (1) and Ba(ReO4)I⋅2H2O (2) were obtained upon evaporation of aqueous solutions at 95 – 100 °C. Both compounds are isostructural to the previously reported Ca(ReO4)Cl⋅2H2O and crystallize in orthorhombic symmetry with the space group Cmcm (a = 7.3906(5) Å, b = 14.241(1) Å, c = 7.1032(5) Å for 1 and a = 7.8624(4) Å, b = 14.0202(5) Å, c = 7.7190(3) Å for 2). Both structures can be regarded as pseudo-layered 3D frameworks comprised of AO8X capped square antiprisms (A = Sr, Ba; X = Br, I) and ReO4 tetrahedra which share vertices with formation of slightly distorted tetragonal pseudo-layers linked by OH⋅⋅⋅X hydrogen bonds. The cationic centers (alkaline earths and rhenium) adopt a litharge-like arrangement. The structure seems to be very sensitive to the ratio of A2+ and X− constituents; it is as yet observed with calcium, only as a chloride, with strontium, only as a bromide, and with barium, only as an iodide.

Copiapite-group minerals are among the most common hydrated iron sulfate minerals in a variety of geological environments on Earth. They are also believed to be widespread on the Martian surface. The transformation and stability of the copiapite-group minerals are examined in this study using a diverse array of methods, including low- (LT) and high-temperature (HT) single-crystal X-ray diffraction (SCXRD), LT- and HT-powder X-ray diffraction (PXRD), vacuum powder X-ray diffraction, HT-Raman spectroscopy, magnetization and heat capacity measurements. The research is conducted over a broad temperature range (−175–740 °C) and under vacuum (∼ 600 Pa) conditions that are partially similar to those found on the Martian surface (from −153 °C to over 20 °C and ∼ 600 Pa). The obtained results indicate that aluminocopiapite, (Al0.54Fe3+0.13)Σ0.67Fe3+4(SO4)6(OH)2(H2O)20, is unstable under low vacuum conditions and undergoes a structural transition to a post-aluminocopiapite phase, (Al0.63Fe3+0.04)Σ0.67Fe3+4(SO4)6(OH)2(H2O)12.44, with a significantly lower water and iron content and a higher aluminum content. Schwertmannite, Fe3+16O16(OH)9.6(SO4)3.2·10H2O is formed as a film/shell on the crystal surface of post-aluminocopiapite via a single crystal-to-single crystal (SC-SC) topotactic transformation and exsolution. After 14 days of exposure to air, the post-aluminocopiapite crystal with schwertmannite shell undergoes a reversible process, reverting to its initial aluminocopiapite state. A closely analogous transformation, involving partial dehydration, was observed for copiapite, Fe2+Fe3+4(SO4)6(OH)2(H2O)20, demonstrating that this behavior is a general feature of the copiapite group.It is therefore unlikely that copiapite-group minerals would exist on the surface of Mars and in comparable extraterrestrial environments in their initial form. Instead, under Mars surface conditions with low vacuum, post-copiapites and schwertmannite may be among the most common minerals in hydrated iron sulfate mineral associations. This is relevant for decoding past geo- and climatic environments on Mars and for selecting the conditions for the return of intact samples collected by rovers to Earth.

Two new copper triethanolamine (tea) complexes, [Cu(tea)(H2O)(2)](SeO4)center dot H2O (1) and [Cu(tea)(H2O)(2)](BeF4)center dot H2O (2) were obtained from aqueous solutions. Their crystal structures are orthorhombic (sp. gr. Pbca) with the following unit cell parameters: a = 12.6763 (2) angstrom, b = 14.9699 (2) angstrom, c = 15.2092 (2) angstrom, V = 2886.14 (7) angstrom 3 (for 1) and a = 12.3858 (2) angstrom, b = 14.8016 (2) angstrom, c = 15.0535 (2) angstrom, V = 2759.75 (7) angstrom 3 (for 2). Both 1 and 2 are full structural analogs of the previously reported [Cu(tea)(H2O)(2)](SO4)center dot H2O sulfate and contain the pseudooctahedral [Cu(tea)(H2O)(2)](2+) cations, tetrahedral TX42- anions and hydration water molecules which form a complex hydrogen-bonded network. The tetrapodal tea ligand and two water molecules form a distorted octahedron around Cu2+ with four relatively short (1.95 - 2.03 angstrom; Cu-N and Cu-O) and two longer (2.30 - 2.38 angstrom; Cu-O) bonds, in agreement to the expected Jahn - Teller distortion for the 3d(9) configuration. The existence of full isostructural series between sulfates, selenates, and fluoroberyllates presents a manifestation of chemical analogy where chemically dissimilar anions ([TO4](2-) vs. [BeF4](2-)) can play identical structure-directing roles. However, this phenomenon is not universal but is governed by strict boundary conditions related to cation properties, anion stability, and synthetic protocol. As in the case of (enH(2))[Cu (H2O)(4)(TX4)](2), the three compounds [Cu(tea)(H2O)(2)](TX4)center dot H2O (TX4 = SO42-, SeO42-, and BeF42-) were found to be isostructural. The key structural feature is the specific chemical environment of the copper-containing complex cation which only weakly interacts (via hydrogen bonding) with the tetrafluoroberyllate anion preserving its integrity.

Formation of guanidinium and 4-aminoguanidinium cations with 18-crown-6 ether was observed upon interaction of the respective thiosulfates and crown ether. The new compounds [(CN3H6)2(C12H24O6)][(CN3H6)2(C12H24O6)(H2O)2](S2O3)2 (1) and [(CN4H7)2(C12H24O6)]2(S2O3) (2), have been characterized by single-crystal and powder diffraction, IR and Raman spectroscopy, and topological analysis. The unit cell parameters are: a = 7.78660(1) Å, b = 9.9999(2) Å, c = 16.7675(3) Å, α = 97.9586(2)°, β = 96.4350(2)°, γ = 99.3458(2)°, space group P-1 for 1 and a = 10.0887(2) Å, b = 17.9587(3) Å, c = 14.1896(3) Å, β = 103.5963(2)°, γ = 99.3458(2)°, space group P21/c for 2. The structures can be referred to as complex hydrogen-bonded 3D networks. In both structures, the crown ether ligands coordinate two (amino)guanidinium cations; in 1, the crown ether molecules and guanidinium cations exhibit two different environments. The size and shape complementarity between the relatively small thiosulfate anions and the cationic complexes is also a critical factor: with the smaller guanidinium cation, the resulting void space is occupied by water molecules, which provide additional stabilization. In contrast, the structure containing the larger aminoguanidinium cation is anhydrous.

The reaction between anhydrous BaX2 (X = Cl, Br) and Ba(SCN)2 results in the formation of two novel compounds with the general formula BaX(SCN), where X = Br-(I) and I-(II). The new compounds have been characterized by single-crystal X-ray diffraction and vibrational (IR and Raman) spectroscopy. Both compounds correspond to known, yet modestly represented, structure types. Compound I is monoclinic with the unit cell parameters a = 5.9873(2) & Aring;, b = 4.7074 (2) & Aring;, c = 8.8044(3) & Aring;, beta = 99.121(3)degrees; space group P21/m, which is isostructural to compounds BaCl(SCN) and BaCl(OCN). The crystal structure of I is analogous to that of the respective chloride thiocyanate and is based on the litharge-type layers, formed by edge-shared anion-centered BrBa4-tetrehedra. Compound II is orthorhombic with the unit cell parameters a = 9.3150(6) & Aring;, b = 4.8168(2) & Aring;, c = 11.9968(7) & Aring;; space group Pnma, and it is isostructural to compounds PbCl(SCN) and o-BaI(OCN). The crystal structure of II is based on edge-shared anion-centered IBa4-tetrahedra, which form a tetrahedral framework. The DFT studies on the relative stability of possible polytypes indicate that, contrary to BaI(OCN), BaI(SCN) is unlikely to exhibit dimorphism. We also discuss the crystal chemical and topological relationships among the three known structural families of MX(ABC) compounds (M = metal cation, X = halide anion, and ABC-linear triatomic anion), as well as their relations to the PbFCl, PbClI, and Nd2O2Te archetypes.

Thermal expansion of the mineral soddyite, (UO2)2SiO4(H2O)2, and structurally related synthetic compound Na2(UO2)2SiO4F2 ( NAUSIF ) has been studied by means of high-temperature single-crystal and powder X-ray diffraction. The mineral is orthorhombic, Fddd, while NAUSIF is tetragonal, I41/amd. The framework structures of both compounds are comprised of either neutral [(UO2)2(SiO4)(H2O)2] or negatively charged [(UO2)2(SiO4)F2]2- chains of similar topology. In the structure of soddyite, the chains cross at the angle of 72 degrees, while in NAUSIF of 90 degrees. Upon increasing temperature, the acute inter-chain angles in soddyite increase due to hinge deformations, the overall symmetry approaching tetragonal. The mineral is stable below 325 +/- 25 degrees & Scy;; between 325 and 640 degrees & Scy;, the decomposition products cannot be identified unambiguously and contain significant amount of amorphous phases; at higher temperatures, a mixture of U3O8 polymorphs is formed. NAUSIF is stable until its melting point of 625 +/- 25 degrees & Scy;. The thermal expansion of both compounds is strongly anisotropic; for NAUSIF , it is due to difference in bond strength in the uranium and sodium polyhedra. Anisotropic thermal expansion of soddyite is controlled by shear deformations of the structure upon the temperature rise.

Single crystals of two new calcium perrhenates, anhydrous Ca(ReO 4 ) 2 ( 1 ) and K 2 Ca 3 (ReO 4 ) 8 ·4H 2 O ( 2 ), were prepared during solid-state and solution attempts to prepare the potassium analog of NaCa(ReO 4 ) 3 . Both structures can be regarded as frameworks comprised of vertex-sharing CaO 8 and ReO 4 polyhedra. 1 is a complete structural analog of Sr(ReO 4 ) 2 while 2 corresponds to its own structure type. It is also the first hydrated binary perrhenate to date. We discuss the similarities and differences in the structures of alkaline earth perrhenates and pertechnetates; existence of more complex and elegant metal-perrhenate architectures is predicted.

We investigated crystal structures and the mechanism of thermal expansion of weeksite and its synthetic analogues (K-, Rb-, Cs-) using a combination of geometrical-topological analysis and empirical methods (powder X-ray diffraction, infrared spectroscopy, scanning electron microscopy, single-crystal and powder X-ray variable-temperature diffraction). The weeksite sample studied herein was collected at the Anderson mine, Yavapai County, Arizona, USA. Its synthetic analogues were prepared using high-temperature approaches in sealed silica tubes. Natural weeksite is stable up to 860 +/- 10 degrees C; it dehydrates between 100-200 degrees C. Its synthetic analogues with Rb and Cs are stable at least until 1000 degrees C. Their thermal expansion is strongly anisotropic due to shear deformations of the crystal structure. The framework in the structure of weeksite can be regarded as a sequence of uranyl silicate layers linked by SiO4 tetrahedra. With increasing temperature, the angles at the Si-O-Si 'hinges' change, which causes the shear deformations. The differences in the thermal behaviour, including expansion anisotropy, are probably due to the nature (size) of the alkali cations occupying the cavities in the framework. The partial or complete replacement of Rb+ by Cs+ illustrates the zeolite-like nature of the uranyl silicate framework in weeksite. Therefore, its structure can be considered a possible candidate for the selective immobilization of 137Cs+ upon storing nuclear waste with little interference from the more abundant Na+ and K+.

The rapid development of the chemistry of fluorooxoborates is associated with their important role as valuable optical materials. In this work, we report the first two silver representatives of the family, Ag2B5O8F (1) and Ag3B5O8F2 (2). Both structures are based on pentaborate groups with different degrees of "fluorination": 1 contains interpenetrating frameworks composed of [B5O10F] fundamental building units, while 2 consists of layers of [B5O10F2].

Interaction between aqueous solutions of imidazole and H2BeF4 resulted in the formation of a new compound, namely, (C3H5N2)3[Be2F7]. The new fluoroberyllate crystallized in a hexagonal symmetry in a non-centrosymmetric group R32 (a = 9.6083(4) & Aring; and c = 15.7796(5) & Aring;). The structure of the new compound contained fully ordered imidazolium cations C3H5N2+ (which is a relatively rare structural phenomenon) and the "diortho" heptafluorodiberyllate anion ([Be2F7]3-), which interacted via hydrogen bonding. The imidazolium cation formed two strong bonds with two different [Be2F7]3- anions, which, in turn, accepted six hydrogen bonds from the six different imidazolium cations. To date, formation of the "diortho" fluoroberyllate anion is rarely reported, and the reported structure is just a second example containing organic cations. In accordance with the non-centrosymmetric character of the structure, the compound is SHG active, yet the response is relatively small.

A new family of organic-inorganic double sulfates formed by 1-methylpiperazinediium cation (C5H14N2 = 1-mppzH2) and inorganic dications, (1-mpipH2)[M(H2O)6](SO4)2 center dot H2O (M = Mg, Mn, Fe, Co, Ni, Zn, and Cd), has been prepared. All compounds are isostructural to each other. Their crystal structure is comprised of inorganic [M(H2O)6]2+ and organic 1-mppzH22+ cations, sulfate anions and hydration water molecules, linked by a complex net of hydrogen bonds into a 3D network. In addition, two side products, (1-mppzH2)(SO4)center dot 2H2O and (1-mppzH2)(HSeO4)2, were observed. The TGA data indicate that thermal decomposition proceeds in several stages, including dehydration. The nature of the final product essentially depends on the nature of the divalent metal dependent on its reducibility and oxo/chalcophylicity. The crystal structures of the double sulfates are discussed in comparison with those containing some structurally related organic diammonium cations. While selenate analogs of these compounds could not be prepared, we predict existence of isostructural or a closely related family with a tetrahedral dianion similar in charge and size, namely tetrafluoroberyllate, which may be of interest to the chemistry of beryllium.

Three new nickel-based representatives of the so-called “layered hydroselenite” family have been characterized by single-crystal X-ray diffraction. In addition to the (enH2)[Ni(HSeO3)2Br2], the last missing member of the ethylenediammonium – transition metal hydroselenite-halide family, we were able to characterize the first members of a new family of compounds based on the N,N′-dimethylethylenediammonium cations, (dmedaH2)[Ni(HSeO3)2X2], X = Cl and Br. We compare the structural peculiarities of layered hydroselenites “stuffed” by the (enH2)2+ and (dmedaH2)2+ cations and predict existence of new series in this peculiar layered family.

Interaction of A(HSeO3) [A = K, Rb, Cs, (NH4)] and CdX2 (X = Cl, Br) in aqueous solutions results in crystallization of multinary hydroselenite halides. The overwhelming majority of the products correspond to the ACd(HSeO3)X2 composition and crystallize in triclinic symmetry similarly to the recently reported ACu(HSeO3)X2. Yet, the only exception is KCd(HSeO3)2Br, which expands the chemistry of the “layered hydroselenite” An(H2O)m[M(HSeO3)2Xn] family (M = Cu, Co, Zn; n = 1, 2). Formation of the two possible stoichiometries of the metal hydroselenite halide frameworks, [M(HSeO3)X2]– vs. [M(HSeO3)2X]–, (M = Cu, Cd; X = Cl, Br) is likely to depend on both the synthesis conditions and the r(A+)/r(X–) ratio. The potassium-free substructure of the triclinic ACd(HSeO3)X2 is represented by a planar net comprised of trans-CdO2X4 octahedra and hydroselenite anions. If the dimer of anions instead of the monomer is considered a secondary building unit (SBU), the net acquires a kagome net-like topology. The potassium-free substructure of monoclinic KCd(HSeO3)2Br is represented by planar nets, and upon considering SBU = (HSeO3)2 instead of (HSeO3), one obtains a simple square net.

Single crystals of two new calcium perrhenates, anhydrous Ca(ReO4)2 (1) and K2Ca3(ReO4)84H2O (2), were prepared during solid-state and solution attempts to prepare the potassium analog of NaCa(ReO4)3. Both structures can be regarded as frameworks comprised of vertex-sharing CaO8 and ReO4 polyhedra. 1 is a complete structural analog of Sr(ReO4)2 while 2 corresponds to its own structure type. It is also the first hydrated binary perrhenate to date. We discuss the similarities and differences in the structures of alkaline earth perrhenates and pertechnetates; existence of more complex and elegant metal-perrhenate architectures is predicted.

A synthetic analog of mourite (SM), (UO2)Mo5O14(OH)4(H2O)2, has been hydrothermally synthesized at 220 degrees & Scy; and characterized using single-crystal X-ray diffraction, single-crystal and powder X-ray diffraction studies at non-ambient temperatures, X-ray photoelectron spectroscopy, infrared spectroscopy, thermal, and chemical analyses. SM is monoclinic, P2/c, a = 9.9063(6), b = 7.1756(4), c = 12.2105(7) & Aring;, beta = 102.496(6)degrees, V = 847.41(9) & Aring;3; the crystal structure has been refined to R1 = 0.043. The chemical composition of the SM is (the Mo2O5:MoO3 ratio obtained from X-ray photoelectron spectroscopy, H2O by stoichiometry; wt.%): Mo2O5 = 4.61, MoO3 = 61.06, UO3 = 26.95, H2O = 6.76, total 99.38. The empirical formula calculated on the basis of 22 oxygen atoms per formula unit with MoV + MoVI = 5 is (UVI1.03O2)[(MoVI4.63MoV0.37)Sigma 5.00O13.81(OH)0.19] (OH)4(H2O)2. The crystal structure of SM contains UO8, Mo1O6, Mo2O5(H2O), and Mo3O4(OH)2 polyhedra that share vertices and edges to form layers linked by hydrogen bonds only. SM is stable up to 250 +/- 10 degrees & Scy;. Upon heating, continuous dehydration occurs between 160-250 degrees & Scy; until the formation of amorphous products; crystallization above 450 degrees & Scy; produces UO2MoO4, MoO3, and UMo10O32. Below 250 degrees & Scy;, thermal expansion of the compound is strongly anisotropic, with the maximal direction perpendicular to the plane of the layers.

Structures of a family of new hydrated and anhydrous perrhenates of lead and strontium have been determined. Sr(ReO4)(2)H2O is isostructural to Ce(CrO4)(2)H2O and Th(CrO4)(2)H2O; Pb(ReO4)(2)2H(2)O is analogous to Sr(ReO4)(2)2H(2)O and Pb(TcO4)(2)2H(2)O. The compounds Sr(ReO4)(2)6H(2)O, Pb(ReO4)Cl2H(2)O, and {Pb-4(OH)(4)}(ReO4)(4)H2O correspond to new structural architectures. We discuss the similarities and differences in the crystal structures of relatively simple inorganic salts containing tetrahedral oxoanions based on d-elements (MnO4-, TcO4-, ReO4-, CrO42-, and MoO42-); the analogies to tetrahedral p-based hydrido- or fluoroanions (BF4- and AlH4-) exist but are as yet rare.

Two new cesium copper oxosulfates, Cs4Cu7O3(SO4)6 (1) and Cs4Cu7O3(SO4)6[Cu0.2O0.2] (2) which can be considered as representatives of the Cs4Cu7+xO3+x(SO4)6 series with x = 0 and x = 0.2, were prepared in evacuated silica tubes. Both compounds are triclinic, P1 and contain complex polynuclear ensembles of edge-sharing OCu4 tetrahedra decorated by sulfate anions; these building units are arranged into pseudo-layers. The partially disordered Cs+ cations fill the interstices in the structure. The overall topology of the two structures is very similar; however, in 2, the copper-oxide ensembles are additionally stitched by weakly occupied Cu–O fragments into pseudo-chains; this also results in essential disorder in the Cs sublattice. Both structures have very much in common with those of the puninite-euchlorine-fedotovite morphotropic series. We analyze the crystal chemical trends in this morphotropic series.

Single crystals of two new compounds, (C5H14N2)Cr2O7 (1) and (C5H14N2)Cr3O10 (2), were isolated from the reaction products of 1-methylpiperazine and chromium trioxide in aqueous media. The crystal structures have been studied by the means of single-crystal X-ray analysis. The unit cell parameters are: a = 7.8459(1) A, b = 8.8295(1) A, c = 15.8951(2) A, beta = 96.634(1)degrees, space group P21/n for 1 and a = 8.0620(2) A, b = 11.6652(4) A, c = 14.5690(5) A, beta = 100.285(3)degrees, space group P21/c for 2. In contrast to chromate compounds templated by structurally related ethylenediammonium and piperazinediium cations, no monochromate was found in the 1methylpiperazine - water - chromic oxide system. Both structures can be represented as nets of hydrogen bonds between the organic ammonium cations and polychromate anions. We discuss the structural features of various polychromate species (Cr2O72-, Cr3O102-, and Cr4O132-) among structures comprising organic and inorganic cations.