Full-matrix Least-squares Refinement Research Articles

Preparation of Low-Dimensional Cluster Materials: Synthesis, Structure, and Properties of A2Ti2Nb6Cl14O5 (A = K, Rb, Cs), a Series of One-Dimensional Titanium Niobium Oxychlorides

In the course of our systematic investigation of metal oxychloride systems aimed at the preparation of low-dimensional compounds, a new series of niobium oxychloride cluster compounds, A2Ti2Nb6Cl14O5 (A = K, Rb, Cs), was obtained from stoichiometric amounts of ACl (A = K, Rb, Cs), Ti, Nb2O5, NbCl5, and Nb, heated at 750 °C. The crystal structures of the series were determined by single-crystal X-ray diffraction techniques. The compounds crystallize in the monoclinic system, space group C2/c, with unit cell parameters a = 21.503(3) A, b = 8.816(1) A, c = 15.710(2) A, β = 116.21(1)°, V = 2672.1(6) A3, and Z = 4 for A = Rb. The full-matrix least-squares refinement against F 2 converged to R1 = 0.043 (Fo > 4σ(Fo)) and wR2 = 0.089 (all data for A = Rb). The crystal structure of A2Ti2Nb6Cl14O5 has one-dimensional character. It is based on chains formed by (Nb6 ) octahedral niobium clusters connected to each other through apical chloride ligands and titanium counterions. The chains are held together by alkali ...

Assembly and Crystal Structure of a Novel 1‐D Coordination Polymer of Copper (II) with Thiocyanate and 4‐Cyanopyridine

AbstractA novel one‐dimensional coordination polymer, Catena‐poly [bis(4‐cyano‐pyridyl) copper(II)‐di‐thiocyanate], 1∞ [CuII‐(cypy)2(μN.S‐SCN)2] (cypy = 4‐cyano‐pyridyl), was synthesized in a solution reaction of Cu(NO3)2·3H2O, 4‐cyano‐pyridine and KSCN in mole ratio of 1:2:2 at room temperature. Its crystal structure was determined by single‐crystal X‐ray diffraction. The crystal belongs to monoclinic crystal system, space group P21/c with cell parameters a = 1.0719(2), b = 1.8441(4), c =0.9144(2) nm, β = 110.49(3)° and Z = 4. A full‐matrix least‐squares refinement gave R1 = 0. 0393 and wR2= 0.0916 for 1554 reflections having 1 >2σ(I). The crystal is thermally stable up to approximately 170 °C.

A new quasi-one-dimensional niobium oxychloride cluster compound Cs2Ti4Nb6Cl18O6: structural effects of ligand combination.

The new niobium oxychloride cluster compound, Cs2Ti4Nb6Cl18O6, was obtained by solid-state synthesis techniques in the course of our systematic investigation of metal oxychloride systems aimed at the preparation of low-dimensional cluster compounds. Cs2Ti4Nb6Cl18O6 crystallizes in the trigonal system, with unit cell parameters a= 11.1903(7), c = 15.600(2) A, space group P3bar1c, Z = 2. Its crystal structure was determined by single-crystal X-ray diffraction techniques. The full-matrix least-squares refinement against F(2) converged to R(1) = 0.048 (F(o) > 4sigma(F(o))), wR(2) = 0.069 (all data). The structure is based on an octahedral cluster unit (Nb6Cl(i)6O(i)6)Cl(a)6 in which the six edge-bridging oxide ligands are arranged in two sets of three on opposite sides of the Nb6 octahedron. Ti(3+) ions link the clusters through O(i) and Cl(a) ligands to form linear chains running along the c axis. The location of titanium ions correlates with the arrangement of oxide ligands around the Nb6 metal core. The chains interact with each other through additional Ti(3+) and Cs(+) ions. Interchain interactions are significantly weaker than intrachain interactions, resulting in a quasi-one-dimensional character of the overall structure.

BiMn6PO12, A New Bismuth Manganese II/III Oxyphosphate with an Original Manganese–Oxygen Cubic Network

A new bismuth manganese oxyphosphate, BiMn6PO12, with an original cubic structure has been synthesized by solid state reaction from Bi2O3, MnO2, and (NH4)2HPO4 or BiPO4 and Mn3O4 mixtures. Its crystal structure has been determined from single-crystal X-ray diffraction data. It crystallizes in the cubic system with space group Fm3m and unit cell parameter a=9.626(1) Å, Z=4. A full-matrix least-squares refinement yielded R=0.044 and Rw=0.045 for 131 independent reflections with I>2σ(I) collected on a Philips PW100 diffractometer (MoKα radiation). The structure of BiMn6PO12 is characterized by a three-dimensional network of manganese–oxygen bonds. The oxygen atoms form a rhombicuboctahedron. The manganese atoms occupy two-thirds of the square faces of this polyhedron and are at the vertices of cuboctahedra. Manganese and oxygen atoms form a Mn12O24 cage, which constitute the strong basic element of the global building. The PO4 tetrahedron is located within this cage and can be moved between two equivalent orientations. The connection between Mn12O24 entities created little cubic holes occupied by bismuth atoms. In this compound all the manganese atoms are crystallographically equivalent and the mean oxidation state of manganese is +2.67. A superstructure, which could be due to PO4 orientations ordering, was evidenced by an electronic diffraction study. BiMn6PO12 exhibits complicated magnetic behavior with several magnetic transitions both in the paramagnetic state and in the low-temperature ordered state.

Crystal Structure of Lithium-Sodium (Li0.7Na0.3)-Analcime

When Na is substituted by Li in the narrow-pore zeolite analcime Na2[Al2Si4O12]⋅2H2O, the average parameter of the pseudocubic unit cell decreases from 13.67 A in the starting Na-analcime to 13.50 A in Li-analcime. Our structural data for Li-analcime [1] showed that the Li cations lie near the Na-sites in an octahedral arrangement O4(H2O)2 distorted to 4+2 or 3+3. Due to their smaller size, the Li cations are displaced toward the edge of one of the two Si,Al-tetrahedra coordination-linked to the given site, and the symmetry is reduced from Ibca to Pbca. Investigation of the Na–Li isomorphic series in analcimes showed that variation of the ratio of exchange cations leads to discontinuity in the thermal properties of the cation-substituted forms [2]. Thermal dehydration of samples with more than 30% sodium replaced by lithium led to decomposition of the solid solution into two phases, one of which (phase II) demonstrated more significant compression. According to high-temperature powder X-ray diffraction data, during dehydration, phase II undergoes a structural transformation accompanied by a change in unit cell dimensions showing that the cell has transformed from pseudocubic to pseudotrigonal and its volume has significantly decreased. This transformation is attributed to migration of the Na cations from the standard position on the twofold axis based on 4 oxygen atoms to a new position on the pseudothreefold axis based on 3 (+3) oxygen atoms. Samples with the degree of substitution 70% and higher contain phase II alone. At the first stage of our study of this structural transformation, we seek to reveal possible differences in the environment of Na and Li in the starting hydrated sample of (Li0.7Na0.3)-analcime. (Li,Na)-Analcime was obtained by ion exchange from natural analcime (Nidym River, East Siberia), whose crystal structure was refined earlier [3]. Crystals ≤0.20 mm in size were stored in a melt of LiNO3 and NaNO3 in a ratio of 0.95/0.05 at 260°C for 7 days. The ratio of the number of cations in the melt to that in the solid was 50/1. Then the sample was washed in hot distilled water to remove the salt and autoclaved in distilled water at 150°C. The Na content in the sample was determined by flame photometry. The H2O content was estimated from weight loss data obtained by sample calcination to 750°C by the thermogravimetric technique (TG-50, TA 3000, Mettler). The Li content was calculated based on the charge balance for the composition of the Li-analcime framework [1]. The formula of the resulting (Li,Na)-analcime sample is recorded as Li1.30Na0.53[Al1.83Si4.17O12]⋅2.05H2O, Z = 8; percent of Li exchange for Na is 71%. The X-ray diffraction experiment was carried out on a an Enraf-Nonius CAD-4 single crystal automatic diffractometer (MoKα radiation, 2θ = 70°, θ/2θ scan mode). The intensity data were collected twice. Collection in the full sphere of reciprocal space showed that the symmetry of the structure is not lower than orthorhombic. However, because of the wrong choice of cell dimensions in passing to the orthorhombic (pseudocubic) cell we were unable to check the deviation from I-centering of the unit cell. Therefore the intensity data were also collected in 1/8 of the sphere of reciprocal space, and the structure was solved with these data (direct methods, SHELXS-86 [4]). The full-matrix least-squares refinement was carried out anisotropically with SHELXL-93 [5] in space groups Pbca and Ibca using the complete set of F 2. Although there were 88 reflections with F0 > 3σ(F0) (five of these were “observable” reflections with F0 > 4σ), which are forbidden in a body-centered cell, structure refinement in Pbca gave unsatisfactory results. In particular, the T–O distances in the (Si,Al)O4-tetrahedra had wide variations of values in one tetrahedron (1.525-1.690 A). The correlation matrix elements were as high as 0.86. All these effects might be a consequence of understated symmetry [6]. While the Na and Li cations occupy the general positions in the given space group, their expected displacement from the center of the coordination octahedron was not observed.

Crystal Structure of 1,10-Diazonia-18-crown-6 Picrate

The crystal structure of 1,10-diazonia-18-crown-6 picrate (I) was determined in an X-ray diffraction study: space group \(P\overline 1 \), a = 10.516(2), b = 11.595(2), c = 15.470(3) A, α = 78.74(2), β = 70.31(2), γ = 64.38(2)°, Z = 2. The structure was solved by direct methods. The full-matrix least-squares refinement was performed anisotropically to R = 0.060 for all 5275 unique reflections collected (CAD-4 automatic diffractometer, λMoKα). In crystal, compound (salt) I exists as individual complex (ionic) molecules [H2DA18C6]2+⋅2Pic– formed by N–H⋯O type hydrogen bonds and counterion electrostatic attraction forces. In the unit cell of crystal I, there are two such centrosymmetric and crystallographically independent molecules; the constituent molecular ions are slightly disordered. The DA18C6 dications exist in two-angle form, which is their typical conformation.

Synthesis and Structure of Co2[Re6Se8(CN)6]⋅12H2O

The cluster anions [Re6X8(CN)6] 4− were synthesized not long ago [1-4]. Anions of this kind have six terminal cyano groups. These are topological analogs of hexacyanometallate anions [M(CN)6] n−, reacting with transition metal cations to form polymer compounds. The larger size of cluster anions compared to mononuclear ones lead to unusual structures containing large cavities [5-7]. Another interesting feature of large cluster anions is possible stabilization of oligomer cations. For example, interaction of aqueous solutions of [Cu(H2O)6] 2+ with a solution of the tetranuclear anion cyano complex [Re4Te4(CN)12] 4− leads to formation of [Cu4(OH)4][Re4Te4(CN)12] containing a hydroxo cation tetramer [Cu4(OH)4] 4+ [8]. Here we report on the synthesis and structural study of Co2[Re6Se8(CN)6]⋅12H2O containing cobalt cation dimers bridged by water molecules. Experimental. Co2[Re6Se8(CN)6]⋅12H2O (1) was prepared by diffusion of the starting substances in silica gel. For this, Na2SiO3⋅9H2O (12.25 g) was dissolved in H2O (50 ml) and titrated to pH 7 while vigorously stirring with 1 M hydrochloric acid (∼20 ml). The resulting mixture was poured into a U-tube and allowed to stay for 1-2 days until the gel completely polymerized. An aqueous solution containing K4[Re6Se8(CN)6] [2] was applied to the gel in one knee of the U-tube, and an aqueous solution of CoCl2 was applied in the other knee. After 4 weeks, well-faceted orange prisms crystallized in the middle part of the tube. The structure of compound 1 was established by X-ray diffraction analysis. A yellowish orange prismatic single crystal sized 0.08×0.05×0.05 mm was chosen from the gel. The data were collected at 293 K on a Rigaku AFC5R diffractometer with a rotating anode (MoKα radiation, graphite monochromator). Crystal data: Co2Re6Se8C6N6O12H24, mol. wt. 2749.50, monoclinic, with cell parameters a = 9.875(4), b = 16.375(2), c = 12.1875(30) A, β = 96.00(2)°, Vcell = 1959.96(90) A3, space group P21/c, Z = 4, ρcalc = 3.753 g/cm 3. The number of reflections collected was 6280 (2θmax = 60.06°), including 5972 unique reflections (Rint = 0.09). An absorption correction (μ = 26.45 cm –1) was applied using the DIFABS program [9]. The structure was solved by direct methods with SHELX-86. The full-matrix least-squares refinement was carried out anisotropically for Re, Co, and Se atoms with teXsan program package [10]. The water hydrogen atoms were not located. The final R indices were R = 0.0708, wR = 0.0989 for 3692 reflections with I ≥ 2σ(I). Atomic coordinates are given in Table 1; bond lengths, in Table 2. Discussion of results. The structure of [Re6Se8(CN)6] 4− in compound 1 is shown in Fig. 1. The interatomic distances and the anion geometry are analogous to those found for other compounds with octahedral cluster anions [Re6X8(CN)6] 4− [1-7]. While dimerization via the bridging water molecules is not typical for transition metal cations [11], centrosymmetric dimers of Co2+ cations bridged by two water molecules are formed in 1 (Fig. 2). The distances from the bridging oxygen atom to the cobalt atoms are nonequivalent (2.14 and 2.25 A). This leads to a distortion of the Co2O2 rhomb to a parallelogram. The Co–Co distance is 3.43 A, ruling out the presence of a metal—metal bond. Cobalt has a slightly distorted octahedral environment formed by three water molecules (two bridging O2, O2a and one terminal O1) and three nitrogen atoms of the cyanide ligands belonging to three different anions. For the CoO3N3 coordination unit, edge and face geometrical isomers are possible. In this structure, the face isomer is realized (Fig. 2). The Co–N distance is 2.05-2.09 A; this value is typical for the Co2+–N coordination bond.

Synthesis, Crystal Structure, and Comparison of Two New Uranyl Vanadate Layered Compounds: M6(UO2)5(VO4)2O5 with M=Na, K

Two new alkali uranyl vanadates, M6(UO2)5(VO4)2O5 with M=Na, K, have been synthesized by solid state reactions and their structures determined from single-crystal X-ray diffraction data. They crystallize in the monoclinic system with space group P21/c. Unit cell b, c, and β parameters are almost identical in both compounds while the a parameter in the Na compound is doubled: Na—a=12.584(1) Å, b=24.360(2) Å, c=7.050(1) Å, β=100.61(1)°, V=2124.2 Å3, Z=4, Dmes=5.60(2) g/cm3, Dcal=5.63 g/cm3; K—a=6.856(1) Å, b=24.797(3) Å, c=7.135(1) Å, β=98.79(8)°, V=1198.8 Å3, Z=2, Dmes=5.25(2) g/cm3, Dcal=5.25 g/cm3. A full-matrix least-squares refinement yielded, respectively, R=0.039, Rw=0.043 and R=0.037; Rw=0.046 for 3293 and 2096 independent reflections with I>3σ collected on a Philips PW 1100 diffractometer (MoKα radiation). Both structures are characterized by [(UO2)5(VO4)2O5x]6n−n corrugated layers parallel to the (100) plane. The layers are built up from VO4 tetrahedra, UO7 pentagonal bipyramids, and UO6 distorted octahedra. The UO7 pentagonal bipyramids are associated by sharing opposite equatorial edges to form zig-zag infinite chains (UO5)n parallel to the c axis. These chains are linked together on one side by VO4 tetrahedra and on other side by UO6 octahedra and UO7 corner sharing. Both structures differ simply by the symmetry of the layers. The unit cell contains one centrosymmetric layer in the K compound, whereas in the two-layer unit cell of the Na compound two noncentrosymmetric consecutive layers are related by an inversion center. The layers appear to be held together by the alkali ions. The mobility of the M+ ions within the interlayer space in M6(UO2)5(VO4)2O5 and carnotite analog compounds is compared.

The atomic resolution structure of bucandin, a novel toxin isolated from the Malayan krait, determined by direct methods.

Bucandin is a novel presynaptic neurotoxin isolated from Bungarus candidus (Malayan krait). It has the unique property of enhancing presynaptic acetylcholine release and represents a family of three-finger toxins with an additional disulfide in the first loop. There are no existing structures from this sub-category of three-finger toxins. The X-ray crystal structure of bucandin has been determined by the Shake-and-Bake direct-methods procedure. The resulting electron-density maps were of outstanding quality and allowed the automated tracing of 61 of the 63 amino-acid residues, including their side chains, and the placement of 48 solvent molecules. The 0.97 A resolution full-matrix least-squares refinement converged to a crystallographic R factor of 12.4% and the final model contains 118 solvent molecules. This is the highest resolution structure of any member of the three-finger toxin family and thus it can serve as the best model for other members of the family. Furthermore, the structure of this novel toxin will help in understanding its unique ability to enhance acetylcholine release. The unique structure resulting from the fifth disulfide bond residing in the first loop improves the understanding of other toxins with a similar arrangement of disulfide bonds.

Report on Temperature Dependence of Crystal Structure for Samarium Nitrate Having Metastable Phenomena

The crystal structures of samarium nitrate Sm(NO 3 ) 3 6H 2 O at temperatures 297, 253 and 193 K±1 K were investigated by single crystal X ray diffraction technique. The crystal symmetry at the temperatures was triclinic with space group P \bar1. The structures were solved by using Fourier techniques. The full matrix least-squares refinement for the structure at 297 K led to the residual factors R =0.016 and R w =0.026 for 213 variables and 5078 observed independent reflections. The structures at 253 K and 193 K were solved by using the same methods. The influence of the metastable phenomena on the structures was examined in detail.

Structure refinement of potassium–samarium cyclotetraphosphate KSmP 4O 12

Single crystals of KSmP 4O 12 have been synthesized by a flux method. A single-crystal X-ray diffraction analysis characterized this structure as monoclinic with space group C2/ c (No. 15) and parameters a = 7.861(1), b = 12.415(2), c = 10.569(3) Å, β = 110.78(1)°, Z = 4, V = 964.4(4) Å 3, and D x = 3.48 g·cm −3. A full-matrix least-squares refinement gave R = 0.0285 for 1809 independent reflections. The atomic arrangement of the title compound can be described as a succession of layers extending along the [010] direction. P 4O 12 anions are centered by the planes z = 0 and z = 1/2, whereas chains made by K + and Sm 3+ cations are centered by the planes z = 1/4 and z = 3/4. Samarium and potassium are surrounded by eight and six oxygen atoms, respectively.

Bis-aqua-cobalt(III)-tetramethylchiroporphyrin perchlorate: a selective water metalloreceptor

Bis-aqua-cobalt(III)-tetramethylchiroporphyrin perchlorate [(TMCP)Co(H 2O) 2]ClO 4, was prepared and characterized by 1H NMR and X-ray crystallography. The structure shows unusual features, including a highly ruffled macrocycle, and very strong intra- and inter-molecular hydrogen bonds. Crystal data for [(TMCP)Co(H 2O) 2]ClO 4·MeOH·3H 2O: C 50.5H 71ClCoN 4O 19 orthorhombic, space group P2 12 12 1, a=11.7432(7), b=15.7240(9), c=29.720(2) Å, U=5487.7(6) Å 3, Z=4. Full-matrix least-squares refinement of positional and thermal parameters, using 9641 independent reflections with I>2 σ( I) led to R 1=0.0568.

Structures and phase transitions of the A7PSe6 (A = Ag, Cu) argyrodite-type ionic conductors. II. Beta- and gamma-Cu7PSe6

The crystal structures of two of the three polymorphic forms of the Cu7PSe6 argyrodite compound are determined by means of single-crystal X-ray diffraction. In the high-temperature form, at 353 K, i.e. 33 K above the first phase transition, gamma-Cu7PSe6 crystallizes in cubic symmetry, space group F43m. The full-matrix least-squares refinement of the structure leads to the residual factors R = 0.0201 and wR = 0.0245 for 31 parameters and 300 observed independent reflections. In the intermediate form, at room temperature, beta-Cu7PSe6 crystallizes again in cubic symmetry, but with space group P2(1)3. Taking into account a merohedric twinning, the refinement of the beta-Cu7PSe6 structure leads to the residual factors R = 0.0297 and wR = 0.0317 for 70 parameters and 874 observed, independent reflections. The combination of a Gram-Charlier development of the Debye-Waller factor and a split model for copper cations reveals the possible diffusion paths of the d10 species in the gamma-Cu7PSe6 ionic conducting phase. The partial ordering of the Cu+ d10 element at the phase transition is found in concordance with the highest probability density sites of the high-temperature phase diffusion paths. A comparison between the two Cu7PSe6 and Ag7PSe6 analogues is carried out, stressing the different mobility of Cu+ and Ag+ and their relative stability in low-coordination chalcogenide environments.

Cu 3(SeO 3) 2Cl 2: a new oxochloride of copper(II) and selenium(IV)

Cu 3(Se 2O 3) 2Cl 2 crystallises in the triclinic system with the space group P 1 ̄ ; the cell parameters are a=6.1240(4) A ̊ , b=7.7880(5) A ̊ , c=8.5170(6) A ̊ , α=92.755(4)°, β=95.735(4)°, γ=92.853(4)° and Z=2. Full-matrix least-squares refinement gave an R value of 0.05 using 2246 independent reflections. The structure consists of [Cu 3O 5Cl 2] n sheets parallel to (001) of infinite strings of edge-sharing copper polyhedra held together by [SeO 3E] tetrahedra; these sheets are connected along the c-axis by dimers of edge-shared [Cu3O 2Cl 2] square planes. The structure reveals a peculiar oxygen atom bonding scheme and tunnels in which the lone pair of selenium atoms and chlorine atoms interact.

Syntheses and spectroscopic and structural characterization of molybdenum(VI) citrato monomeric raceme and dimer, K4[MoO3(cit)].2H2O and K4[(MoO2)2O(Hcit)2].4H2O.

Investigation of the aqueous coordination chemistry for citrate and molybdenum(VI) resulted in the isolation of molybdenum(VI) citrato monomeric raceme and dimer K4[MoO3(cit)].2H2O (1) and K4[(MoO2)2O(Hcit)2].4H2O (2) (H4cit = citric acid). Complex 1 can serve as the first structurally characterized monomeric citrato molybdate and may represent an early mobilized precursor in the biosynthesis of FeMo-co (FeMo-cofactor). The two complexes have been characterized by elemental analyses and IR and NMR spectroscopies. The IR and NMR spectra are consistent with a monomeric species or a monooxo-bridged dinuclear structure, as revealed by a single crystal X-ray diffraction study. Compound 1 is monoclinic space group P2(1)/c with a = 7.225(1) A, b = 9.151(2) A, c = 22.727(2) A, beta = 94.93(1) degrees, V = 1497.1(7) A3, and Z = 4. Full-matrix least-squares refinement resulted in residuals of R = 0.027 and Rw = 0.032. The molybdenum atom forms an octahedral coordination with three oxo groups and one tridentate citrate, in which the latter is coordinated through the alkoxy and vicinal carboxyl and much more weakly by one of the two terminal groups [2.411(3) A]. Compound 2 is triclinic space group P1 with a = 8.2728(8) A, b = 8.9514(8) A, c = 10.0605(9) A, alpha = 101.673(8) degrees, beta = 100.672(7) degrees, gamma = 112.938(7) degrees, V = 642.5(3) A3, and Z = 1. Full-matrix least-squares refinement resulted in residuals of R = 0.033 and Rw = 0.039. The complex anion contains a linear (O2Mo)O(MoO2) core with the bridging oxo group lying at the center of inversion symmetry (Mo-Ob-Mo, 180 degrees). Each citrate ligand is three-coordinated to one molybdenum atom through the deprotonated hydroxy, alpha-carboxyl, and one beta-carboxyl group, making each metal atom six-coordinate.

One-step Syntheses of p- and m-Xylylene-bridged Azacalixarenes and Their Rigid Molecular Skeletons

Novel self-filled azacalixarenes were synthesized following a simple method. The structure of a p-xylylene-bridged compound was investigated by X-ray crystallographic analysis. Compound 1: C42H44 O4N2, monoclinic, space group C2/c, a = 17.236 (4), b = 9.244 (3), c = 22.217 (4) Å, β = 101.23 (1)°, D calc 1.226 g/cm3, V=3472 (1)Å3,Z=4,R = 0.042. The final cycle of full-matrix least-squares refinement was based on 2201 observed reflections [I>3.00[sgrave](I)] and 284 variable parameters. Dynamic NMR and MM3 calculations were also employed to study the structures in solution. Azacalix[4] skeletons are rigidly fixed in shallow cone conformations and bridging xylylene units (p- and m-) are located in the cavities of the cyclic skeletons. Intra-cavity hydrogen bonds between OH and N atoms localize at low temperatures. The free energy of the localization was estimated to be 10.8 and 11.2 kcal mol−1 for p- and m-xylylene-bridged compounds, respectively.

H 3NNH 3] 2K 2MnMo 9O 32·(NH 3)·3H 2O: synthesis and crystal structure determination of a novel heteropolyoxometallate related to the Waugh structure

A novel heteropolyoxometallate with the formula [H 3NNH 3] 2K 2MnMo 9O 32·(NH 3)·3H 2O has been prepared in water solution. The crystal structure of the title compound was determined by the single-crystal method. This new mixed metal anionic complex crystallizes in the rhombohedral space group R3 (No. 146) with a= b=15.873(5), c=12.344(6) Å, γ=120°. The disordered structure contains three molecules in the unit cell. Full-matrix least-squares refinements of the title complex yielded final reliability ( R) factors of 0.0356 ( Rw=0.0868) with a goodness-of-fit (GOF, Σ 2) value of 1.099 based on 1430 [ I>2 σ( I)] observed reflections. All Mo and Mn atoms are six-coordinated octahedrally to form a Mn-centered cage with a Mo 9O 32 group as the framework.

X-RAY CRYSTALLOGRAPHIC INVESTIGATIONS AND CHARACTERIZATIONS OF THREE MIXED ANIONIC HEXACYANO COMPLEXES

The mixed anionic complexes, Cd3 1l[(CrIII/IrIII)(CN)6]2 13H2O, Co3 11[(CoIII/IrIII)(CN)6]2-13H2O, and Pd3 II[(CrIII/IrIII)(CN)6]2 13H2O, crystallize in the cubic centrosymmetric space group Fm3m (No. 225) with αo= 10.884(1), 10.396(1), and 10.455(2)Å, respectively. The disordered structures contain 11/3 molecules in the unit cell. Full-matrix least-squares refinements yielded final reliability (R) index factors of 0.040, 0.050, and 0.069 with ‚goodness-of-fit’ (GOF, ∑2) values of 1.26, 1.25, and 1.11, respectively. All metal atoms in each compound are six-coordinate octahedral and the cationic divalent metal atoms are linked to the (1:1) mixed trivalent metal atoms by cyanide bridging. Networks of hydrogen-bonding are setup within cavities of the crystal lattices (created by molecular disordering). Characterization of each hexacyano complex includes physical property determinations, conoscopic studies, I. R. spectroscopic identifications, and thermal gravimetric analyses (TGA). Selective bond distances and angles are tabularized.

Synthesis and structural investigation of a novel mixed cationic/anionic hexacyanometallate tetradecahydrate

[(1:2)Zn II/Mn II] 3[(1:2)Ir III/Co III(CN) 6] 2·14H 2O ( I) has been synthesized and structurally analyzed using single-crystal diffractometry. Full-matrix least-squares refinement yielded final reliability factors of R=0.033 and R w=0.023 with a `goodness-of-fit' (GOF, Σ 2) of 1.13 based on 118 unique reflections. The complex crystallizes in the cubic space group Fm 3m (No. 225) with a=10.408(1) Å. For Z=1 1/3, the calculated density is 1.827 Mg m −3 [exp., 1.81(2) Mg m −3]. A thermal gravimetric analysis revealed 14 water molecules per formula unit. All metal atoms are six-coordinated octahedrally and linkages between the mixed divalent cationic and mixed anionic metal atoms are accomplished by cyanide bridging. A hydrogen-bonding network is set up within cavities of the crystal lattice created by molecular disorder. Conoscopic, IR, and digital SEM/EDS elemental results are presented as well as important bond and contact distances.

Crystal growth and structure of V 2VSe 2IVO 9; comparison with V 2Te 2O 9

High quality single crystals of V 2Se 2O 9 have been obtained as a side compound during a study of the CuCl 2-V 2O 5-SeO 2 system. V 2Se 2O 9 crystallises in the monoclinic system, space group P2 1/n with a = 8.0560(2), b=10.3650(2), c = 8.4500(2) Å, β = 102.893(2) °, Z = 4 and ρ x =3.90 g/cm 3. Full matrix least-squares refinement gave an R = 0.0347 and R w = 0.0802 using 2232 independent reflections. The structure is built up by very distorted octahedra occupied by V 5+ sharing one edge and one apex to form [V 4O 18] 16− entities interconnected by SeO 3E tetrahedra (E designs the 4s 2 lone pair of the Se (IV) cation). V 2Se 2O 9 is not isostructural with V 2Te 2O 9, in which the V 5+O 6 octahedra share edges to form along [011] infinite chains linked together via Te 2O 5E 2 groups.