Two polymorphs of bis(2-carbamoylguanidinium) fluorophosphonate dihydrate.

Two polymorphs of bis(2-carbamoylguanidinium) fluorophosphonate dihydrate, 2C(2)H(7)N(4)O(+)·FO(3)P(2-)·2H(2)O, are presented. Polymorph (I), crystallizing in the space group Pnma, is slightly less densely packed than polymorph (II), which crystallizes in Pbca. In (I), the fluorophosphonate anion is situated on a crystallographic mirror plane and the O atom of the water molecule is disordered over two positions, in contrast with its H atoms. The hydrogen-bond patterns in both polymorphs share similar features. There are O-H···O and N-H···O hydrogen bonds in both structures. The water molecules donate their H atoms to the O atoms of the fluorophosphonates exclusively. The water molecules and the fluorophosphonates participate in the formation of R(4)(4)(10) graph-set motifs. These motifs extend along the a axis in each structure. The water molecules are also acceptors of either one [in (I) and (II)] or two [in (II)] N-H···O hydrogen bonds. The water molecules are significant building elements in the formation of a three-dimensional hydrogen-bond network in both structures. Despite these similarities, there are substantial differences between the hydrogen-bond networks of (I) and (II). The N-H···O and O-H···O hydrogen bonds in (I) are stronger and weaker, respectively, than those in (II). Moreover, in (I), the shortest N-H···O hydrogen bonds are shorter than the shortest O-H···O hydrogen bonds, which is an unusual feature. The properties of the hydrogen-bond network in (II) can be related to an unusually long P-O bond length for an unhydrogenated fluorophosphonate anion that is present in this structure. In both structures, the N-H···F interactions are far weaker than the N-H···O hydrogen bonds. It follows from the structure analysis that (II) seems to be thermodynamically more stable than (I).

Mixed crystals of 2-carbamoylguanidinium with hydrogen fluorophosphonate and hydrogen phosphite in the ratios 1:0, 0.76 (2):0.24 (2) and 0.115 (7):0.885 (7).

The title compounds, 2-carbamoylguanidinium hydrogen fluorophosphonate, C(2)H(7)N(4)O(+)·HFO(3)P(-), (I), 2-carbamoylguanidinium-hydrogen fluorophosphonate-hydrogen phosphite (1/0.76/0.24), C(2)H(7)N(4)O(+)·0.76HFO(3)P(-)·0.24H(2)O(3)P(-), (II), and 2-carbamoylguanidinium-hydrogen fluorophosphonate-hydrogen phosphite (1/0.115/0.885), C(2)H(7)N(4)O(+)·0.115HFO(3)P(-)·0.885H(2)O(3)P(-), (III), are isostructural with guanylurea hydrogen phosphite, C(2)H(7)N(4)O(+)·H(2)O(3)P(-) [Fridrichová, Nemec, Císarová & Nemec (2010). CrystEngComm, 12, 2054-2056]. They constitute structures where the hydrogen phosphite anion has been fully or partially replaced by hydrogen fluorophosphonate. The title structures are the fourth example of isostructural compounds which differ by the presence of hydrogen fluorophosphonate and hydrogen phosphite or fluorophosphonate and phosphite anions. Moreover, the present study reports structures with these mixed anions for the first time. In the reported mixed salts, the P and O atoms of either anion overlap almost exactly, as can be judged by comparison of their equivalent isotropic displacement parameters, while the P-F and P-H directions are almost parallel. There are strong O-H···O hydrogen bonds between the anions, as well as strong N-H···O hydrogen bonds between the 2-carbamoylguanidinium cations in the title structures. Altogether they form a three-dimensional hydrogen-bond pattern. Interestingly, rare N-H···F interactions are also present in the title structures. Another exceptional feature concerns the P-O(H) distances, which are about as long as the P-F distance. The dependence of P-F distances on the longest P-O distances in FO(3)P(2-) or HFO(3)P(-) is presented. The greater content of hydrogen phosphite in the mixed crystals causes a larger deformation of the cations from planarity.

Tris(2-carbamoylguanidinium) hydrogen fluoro-phospho-nate fluoro-phospho-nate monohydrate.

The title structure, 3C(2)H(7)N(4)O(+)·HFPO(3) (-)·FPO(3) (2-)·H(2)O, contains three independent 2-carbamoylguanidinium cations, one fluoro-phospho-nate, one hydrogen fluoro-phospho-nate and one water mol-ecule. There are three different layers in the structure that are nearly perpendicular to the c axis. Each layer contains a cation and the layers differ by the respective presence of the water mol-ecule, the hydrogen fluoro-phospho-nate and fluoro-phospho-nate anions. N-H⋯O hydrogen bonds between the guanylurea mol-ecules that inter-connect the mol-ecules within each layer are strong. The layers are inter-connected by strong and weak O-H⋯O hydrogen bonds between the anions and water mol-ecules, respectively. Inter-estingly, the configuration of the layers is quite similar to that observed in 2-carbamoylguanidinium hydrogen fluoro-phospho-nate [Fábry et al. (2012). Acta Cryst. C68, o76-o83]. There is also present a N-H⋯F hydrogen bond in the structure which occurs quite rarely.

N-[Amino(imino)methyl]uronium tetrafluoroborate.

In the title compound, C(2)H(7)N(4)O(+)·BF(4) (-), inter-molecular N-H⋯O hydrogen bonds connect the cations into chains parallel to the c axis, with graph-set motif C(4). These chains are in turn connected into a three-dimensional network by inter-molecular N-H⋯F hydrogen bonds. The B-F distances distances in the anion are not equal.

Structure of the high-temperature phase of caesium nitrate - the importance of high-resolution data.

A single-crystal structure determination of the cubic phase of CsNO3 based on data collected at 439 K up to sinθmax/λ = 0.995000 Å-1, i.e. to an unprecedentedly high-θ value, is reported. The structure has been refined in Pm3m (Z = 1). Analysis of the difference electron-density maps revealed that the most appropriate model is the twelve-orientation model with the Cs, N, O1 and O2 atoms situated on the Wyckoff positions 1a, 6f, 6f and 24l, respectively, rather than the eight-orientation aragonite model with the Cs, N and O atoms situated on the Wyckoff positions 1a, 8g and 24m, respectively. Both models, however, show close similarities if the large anisotropic displacement parameters of the O atoms in the eight-orientation aragonite model are taken into account. The reason for this is shown to lie in the smeared electron density around the positions of the disordered [NO3]- anion.

Low-temperature phases of dicalcium barium hexakis(propanoate).

The structure determinations of phases (II) and (III) of barium dicalcium hexakis(propanoate) {or poly[hexa-µ4-propanoato-bariumdicalcium], [BaCa2(C3H5O2)6]n} are reported at 240 and 130 K, respectively [phase (I) was determined previously by Stadnicka & Glazer (1980). Acta Cryst. B36, 2977-2985; our structure determination of phase (I) at room temperature is included in the supporting information]. In the high-temperature phase, the Ba2+ cation is surrounded by six carboxylate groups in bidentate bridging modes. In the low-temperature phases, five carboxylate groups act in bidentate bridging modes and one acts in a monodentate bridging mode around Ba2+. The Ca2+ cations are surrounded by six carboxylate O atoms in a trigonal antiprism in all the structures. The Ba2+ and Ca2+ cations are underbonded and significantly overbonded, respectively, in all the phases. The bonding of the Ba2+ cation increases slightly at the cost of the bonding of Ca2+ cations during cooling to the low-temperature phases. The phase transitions during cooling are accompanied by ordering of the ethyl chains. In room-temperature phase (I), all six ethyl chains are positionally disordered over two positions in the crossed mode, with additional splitting of the ethyl α- and ß-C atoms. In phase (II), on the other hand, there are three disordered ethyl chains, one with positionally disordered ethyl α- and ß-C atoms, and the other two with positionally disordered ethyl ß-C atoms only, and in the lowest-temperature phase (III) there are four ordered ethyl chains and two disordered ethyl chains with positionally disordered ethyl ß-C atoms only.

A new modification of thallium chromate related to the beta-K2SO4 family.

The title structure is a new modification of Tl(2)CrO(4). There are four independent Tl(+) cations and two [CrO(4)](2-) anions in the structure. It is closely related to the already known modification, which belongs to the beta-K(2)SO(4) family with two independent cations and one anion. In both modifications, the cations and anions are situated on crystallographic mirror planes. The volume of the asymmetric unit of the title structure is approximately 0.4% smaller than that of the known modification belonging to the beta-K(2)SO(4) family. The other difference between the two modifications is seen in the environment of the cations. In the title structure, none of the Tl(+) cations is underbonded, in contrast with the modification isostructural with beta-K(2)SO(4). In the beta-K(2)SO(4) family with simple cations, underbonding of one of the constituent cations is typical. The dependence of the unit-cell parameters on temperature does not indicate a phase transition in the interval 90-300 K.

Dipotassium zinc tetra-iodate(V) dihydrate.

The title compound, K(2)Zn(IO(3))(4)·2H(2)O, contains two symmetry-independent K and I atoms. These atoms, as well as the Zn atom, are coordinated by shared O atoms and, moreover, the Zn atom is coordinated by two water mol-ecules in trans positions. The K, Zn and water O atoms atoms are situated in special positions on twofold symmetry axes. The hydrogen atoms are involved in strong O-H⋯O hydrogen bonds and O-H⋯I inter-actions also occur. The crystals of the title compound are, in general, twinned, but the sample used for this experiment was free of twinning.

Poly[[tetra-deca-kis-(µ-propionato)hepta-barium] propionic acid monosolvate tetra-hydrate].

The title compound, {[Ba7(C3H5O2)14]·0.946C3H6O2·4H2O} n , is represented by a metal-organic framework structure that is held together by Ba-O-Ba bonds, as well as by O-H⋯O hydrogen bonds of moderate strength. The structure comprises of four independent Ba2+ cations (one of which is situated on a twofold rotation axis), seven independent propionate and two independent water mol-ecules. The bond-valence sums of all the cations indicate a slight overbonding. There is also an occupationally, as well as a positionally disordered propionic acid mol-ecule present in the structure. Its occupation is slightly lower than the full occupation while the disordered mol-ecules occupy two positions related by a rotation about a twofold rotation axis. In addition, the methyl group in the symmetry-independent propionic acid mol-ecule is also disordered, and occupies two positions. Each propionic acid mol-ecule coordinates to just one cation from a pair of symmetry-equivalent Ba2+ sites and is simultaneously bonded by an O-H⋯Opropionate hydrogen bond. This means that on a microscopic scale, the coordination number of the corresponding Ba2+ site is either 9 or 10. The methyl as well as hy-droxy hydrogen atoms of the disordered propionic acid mol-ecule were not determined.

Crystal structure of poly[µ-aqua-bis(µ3-2-methylpropanoato-κ4 O:O,O':O')dipotassium].

The structure of the title compound, [K2(C4H7O2)2(H2O)] n , is composed of stacked sandwiches, which are formed by cation-oxygen bilayers surrounded by methyl-ethyl hydro-phobic chains. These sandwiches are held together by van der Waals inter-actions between the methyl-ethyl groups. The methyl-ethyl groups are disordered over two positions with occupancies 0.801 (3):0.199 (3). The potassium cations are coordinated by seven O atoms, which form an irregular polyhedron. There is a water mol-ecule, the oxygen atom of which is situated in a special position on a twofold axis (Wyckoff position 4e). The water H atoms are involved in Owater-H⋯Ocarbox-yl hydrogen bonds of moderate strength. These hydrogen bonds are situated within the cation-oxygen, i.e. hydro-philic, bilayer.

Crystal structures of catena-poly[[µ-aqua-di-aqua(µ3-2-methyl-propano-ato-κ4 O:O,O':O')calcium] 2-methyl-propano-ate dihydrate], catena-poly[[µ-aqua-di-aqua-(µ3-2-methyl-propano-ato-κ4 O:O,O':O')strontium] 2-methyl-propano-ate dihydrate] and catena-poly[[µ-aqua-di-aqua-(µ3-2-methyl-propano-ato-κ4 O:O,O':O')(calcium/strontium)] 2-methyl-propano-ate dihydrate].

The crystal structures of catena-poly[[µ-aqua-di-aqua-(µ3-2-methyl-propano-ato-κ4 O:O,O':O')calcium] 2-methyl-propano-ate dihydrate], {[Ca(C4H7O2)(H2O)3](C4H7O2)·2H2O} n , (I), catena-poly[[µ-aqua-di-aqua-(µ3-2-methyl-propano-ato-κ4 O:O,O':O')strontium] 2-methyl-propano-ate dihydrate], {[Sr(C4H7O2)(H2O)3](C4H7O2)·2H2O} n , (II), and catena-poly[[µ-aqua-di-aqua-(µ3-2-methyl-propano-ato-κ4 O:O,O':O')(calcium/strontium)] 2-methyl-propano-ate dihydrate], {[(Ca,Sr)(C4H7O2)(H2O)3](C4H7O2)·2H2O} n , (III), are related. (III) can be considered as an Sr-containing solid solution of (I), with Ca2+ and Sr2+ occupationally disordered in the ratio 0.7936 (16):0.2064 (16). (I)/(III) and (II) are homeotypic with different space groups of Pbca and Cmce, respectively. All the title crystal structures are composed of hydro-philic sheets containing the cations, carboxyl-ate groups as well as water mol-ecules. The hydro-phobic layers, which consist of 2-methyl-propano-ate chains, surround the hydro-philic sheets from both sides, thus forming a sandwich-like structure extending parallel to (001). The cohesion forces within these sheets are the cation-oxygen bonds and O-H⋯O hydrogen bonds of moderate strength. Stacking of these sandwiches along [001] is consolidated by van der Waals forces. The structures contain columns defined by the cation-oxygen inter-actions in which just one symmetry-independent 2-methyl-propano-ate anion is included, together with three water mol-ecules. These mol-ecules participate in an irregular coordination polyhedron composed of eight O atoms around the cation. Additional water mol-ecules as well as the second 2-methyl-propano-ate anion are not part of the coordination sphere. These mol-ecules are connected to the above-mentioned columns by O-H⋯O hydrogen bonds of moderate strength. In (II), the Sr2+ cation, two of the coordinating water mol-ecules and both anions are situated on a mirror plane with a concomitant positional disorder of the 2-methyl-propyl groups; the non-coordinating water mol-ecule also shows positional disorder of its hydrogen atom.

Layered alkali propano-ates M +(C2H5COO)-; M + = Na+, K+, Rb+, Cs.

The title alkali propano-ates poly[(µ5-propano-ato)alkali(I)], M +(C2H5COO)-, with alkali/M + = Na+, K+, Rb+ and Cs+, show close structural similarity, which is manifested by the coordination of the cations by six oxygen atoms in a chessboard motif, forming a bilayer. This bilayer is situated between hydro-phobic layers composed of dangling ethyl chains from the carboxyl-ate groups. Stacking of these two-dimensional sandwiches, which are parallel to (001), forms the title structures. Each metal cation is coordinated by six O atoms in the form of a distorted trigonal prism. One pair of these oxygen atoms belongs to a bridging, bidentately coordinating carboxyl-ate anion, while each of the other four oxygen atoms belongs to different carboxyl-ate groups, which are in a bridging monodentate mode. Despite the close similarity, each of the studied alkali propano-ates crystallizes in a different space group. The atoms are in general positions, except for the cation in K+(C2H5COO)-, which is situated on a mirror plane. Positional disorder of the methyl groups that are disordered over two positions is present in the Na+ and K+ propano-ates, in contrast to the Rb+ and Cs+ propano-ates. In the Na+ compound, the occupational parameters of the disordered methyl groups are different compared to the K+ compound where they are equal. This difference results in doubling of the a unit-cell parameter of the Na+ compound with respect to that of the K+ compound, otherwise the structures are homeotypic. In Cs+ propano-ate, a disorder of the methyl H atoms is observed.

Caesium propano-ate monohydrate.

Caesium propano-ate monohydrate, Cs+·C3H5O2 -·H2O, is composed of two symmetry-independent Cs+ cations, which are situated on the special position 4e of space group P 21 m, one symmetry-independent propano-ate mol-ecule in a general position and a pair of water mol-ecules also situated on special position 4e. Two pairs of these symmetry-independent cations, four propano-ate mol-ecules and two pairs of symmetry-independent water mol-ecules form a repeat unit. These units form columns that are directed along the c axis and possess symmetry mm2. There are four such columns passing through each unit cell. Each column is inter-connected to its neighbours by four bifurcated three-centred Ow-H⋯Op (w = water, p = propano-ate) hydrogen bonds of moderate strength. There are also four intra-molecular Ow-H⋯Op hydrogen bonds of moderate strength within each column. One Cs+ cation is coordinated by six oxygen atoms (two water and four carboxyl-ate) in a trigonal-prismatic geometry, while the other Cs+ cation is coordinated by four water and four carboxyl-ate O atoms in a tetra-gonal-prismatic arrangement.

Rerefinement of poly[di-aqua-bis-(µ3-2-methyl-pro-pano-ato-κ4 O:O,O':O')bis-(µ3-2-methyl-propano-ato-κ3 O:O:O)(µ2-2-methyl-propano-ato-κ3 O:O,O')(2-methyl-propano-ato-κ2 O,O')trilead(II)].

The crystal structure of the title complex, [Pb3(C4H7O2)6(H2O)2] n , was redetermined on basis of modern CCD-based single-crystal X-ray data at 120 K. The current study basically confirms the previous report [Fallon et al. (1997 ▸). Polyhedron, 16, 19-23] at 190 K, but with higher accuracy and precision. In particular, positional disorder of one of the 2-methyl-propano-ate anions over two sets of sites was resolved, showing a refined ratio of the disorder components of 0.535 (9):0.465 (9). The three independent cations in the structure have coordination numbers of [7 + 1], [6 + 1], and [5 + 3], with O atoms belonging either to carboxyl-ate groups or water mol-ecules. This arrangement leads to the formation of sheets parallel to (01), whereby the hydro-phobic 2-methyl-propanyl groups of the anions are oriented above and below the hydro-philic sheets to form a layered structure. Within a sheet, hydrogen bonds of the type Owater-H⋯O are formed, whereas the hydro-phobic groups between adjacent layers inter-act through van der Waals forces.

2-(2-Hydroxy-ethyl)-3-[(2-hydroxy-ethyl)imino]isoindolin-1-one.

In the crystal structure of the title compound, C(12)H(14)N(2)O(3), mol-ecules are packed into layers parallel to (100). Each layer contains centrosymmetric dimers formed by a pair of strong O-H⋯N hydrogen bonds with an R(2) (2)(10) motif, while strong O-H⋯O hydrogen bonds forming C(10) chains connect mol-ecules into a two-dimensional network. Additional stabilization is supplied by weak C-H⋯O hydrogen bonds and weak π-π stacking inter-actions with centroid-centroid distances in the range 3.4220 (7)-3.9616 (7) Å.

Degenerate (identity) chemical reactions in ferroelastic crystals.

The presence of degenerate chemical reactions in crystals is discussed. They take place in some order-disorder phase transitions in crystals. The other category of identity (degenerate) chemical reactions in crystals includes a few examples of domain reorientations with simultaneous hopping of atoms/ions in some ferroelastic crystals. The product of the hopping maybe either identical with the reactant though in a different orientation or a conjugated enantiomorph. In these examples, the hopping atom is either situated in a special position or disordered about it in the paraelastic phase. The article also discusses the definition of identity (degenerate) chemical reactions which do not take into cosideration the reactions in which the reactant and the product are enantiomers or enantiomorphs.

(Tetra-oxidoselenato-κO)tris-(thio-urea-κS)zinc(II).

The title structure, [Zn(SeO(4))(CH(4)N(2)S)(3)], is isomorphous with sulfatotris(thio-urea)zinc(II). In both structures, the Zn(2+) cation is coordinated in a tetra-hedral geometry. The corresponding intra-molecular distances are quite similar except for the Se-O and S-O distances. Although the hydrogen-bonding patterns are similar, there are some differences; in the title structure all the H atoms are involved in the hydrogen-bond pattern, in contrast to the situation in sulfatotris(thio-urea)zinc(II). No reproducible anomalies were detected by differential scanning calorimetry in the range 93-463 K until decomposition started at the higher temperature.

Pyridine-3-carboxamide-telluric acid (1/1).

In the title structure, C6H6N2O·H6O6Te, the pyridine-3-carboxamide and telluric acid mol-ecules are inter-connected by conventional O-H⋯N, N-H⋯O and O-H⋯O hydrogen bonds of moderate strength as well as by π-π inter-actions between the pyridine rings. The strongest hydrogen bond in the structure is formed between a hydroxyl group of the H6TeO6 mol-ecule and the N-pyrimidine N atom. The structure is unusual because of presence of the alternating sheets, which contain H6TeO6 and pyridine-3-carboxamide mol-ecules, respectively. These sheets are aligned parallel to (001).

Bis(3-carbamoylpyridin-1-ium) phosphite mono-hydrate.

Two of the constituent mol-ecules in the title structure, 2C6H7N2O+·HPO32-·H2O, i.e. the phosphite anion and the water mol-ecule, are situated on a symmetry plane. The mol-ecules are held together by moderate N-H⋯O and O-H⋯N, and weak O-H⋯O and C-H⋯Ocarbon-yl hydrogen bonds in which the amide and secondary amine groups, and the water molecules are involved. The structural features are usual, among them the H atom bonded to the P atom avoids hydrogen bonding.

A resonance-assisted intra-molecular hydrogen bond in compounds containing 2-hy-droxy-3,5-di-nitro-benzoic acid and its various deprotonated forms: redetermination of several related structures.

A large number of structural determinations of compounds containing 2-hy-droxy-3,5-di-nitro-benzoic acid (I) and its various deprotonated forms, 2-hy-droxy-3,5-di-nitro-benzoate (II) or 2-carb-oxy-4,6-di-nitro-phenolate (III), are biased. The reason for the bias follows from incorrectly applied constraints or restraints on the bridging hydrogen, which is involved in the intra-molecular hydrogen bond between the neighbouring carb-oxy-lic/carboxyl-ate and oxo/hy-droxy groups. This hydrogen bond belongs to the category of resonance-assisted hydrogen bonds. The present article suggests corrections for the following structure determinations that have been published in Acta Crystallographica: DUJZAK, JEVNAA, LUDFUL, NUQVEB, QIQJAD, SAFGUD, SEDKET, TIYZIM, TUJPEV, VABZIJ, WADXOR, YAXPOE [refcodes are taken from the Cambridge Structural Database [CSD; Groom et al. (2016 ▸). Acta Cryst. B72, 171-179]. The structural features of the title mol-ecules in all the retrieved structures, together with structures that contain 3,5-di-nitro-2-oxidobenzoate (IV), are discussed. Attention is paid to the localization of the above-mentioned bridging hydrogen, which can be situated closer to the O atom of the carboxyl-ate/carb-oxy-lic group or that of the hy-droxy/oxo group. In some cases, it is disordered between the two O atoms. The position of the bridging hydrogen seems to be dependent on the pKa (base) although with exceptions. A stronger basicity enhances the probability of the presence of a phenolate (III). The present article examines the problem of the refinement of such a bridging hydrogen as well as that of the hydrogen atoms involved in the hy-droxy and primary and secondary amine groups. It appears that the best model, in many cases, is obtained by fixing the hydrogen-atom position found in the difference electron-density map while refining its isotropic displacement parameter.