Coordination Polyhedra LaO<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> in Crystal Structures

The Voronoi-Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to analyze the oxygen environment of the lanthanum atoms in the structures of 553 compounds containing 763 crystallographically nonequivalent sorts of LaO_n polyhedra. The La(III) atoms have a C.N. of 4 to 12 with respect to oxygen. The volume of the VDP of La atoms virtually does not depend on the C.N., although the La-O bond length changes by 0.77 Å.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 466–471.Original Russian Text Copyright © 2005 by Vologzhanina, Pushkin, Serezhkin.     

The coordination polyhedra KCl<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> in the crystal structures

The Voronoi-Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to carry out crystal chemical analysis of 141 chlorides containing 245 crystallographic sorts of potassium atoms in the KCl_n coordination polyhedra. The potassium atoms in the crystal structures can coordinate 6 to 12 chlorine atoms, the K-Cl bond lengths varying from 2.81 to 3.91 Å. The radius of spherical domains whose volume coincides with the volume of potassium VDP was found to be virtually independent of the coordination number or the shape of the coordination polyhedron, being equal to 1.93(4) Å. The VDP characteristics were used to analyze the stereochemical features of potassium in the crystal structures.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 1, 2005, pp. 72–80.Original Russian Text Copyright © 2005 by Bikanina, Shevchenko, Serezhkin     

Coordination polyhedra PbX<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (X = F,Cl, Br,I) in crystal structures

The Voronoi-Dirichlet polyhedra (VDP) and the intersecting sphere method were used to analyze the coordination of Pb(II) and Pb(IV) atoms by halogen atoms in the crystal structures of 158 compounds. A decrease in the steric effect of the Pb(II) lone electron pair with a decrease in the electronegativity of the surrounding atoms was established. The influence of the nature of the central atom on the steric effect of the lone pair in the structure of the AX _n ^z? complexes, where X is halogen or oxygen, A = Tl(I), Sn(II), Pb(II), As(III),Sb(III), Bi(III), S(IV), Se(IV), Te(IV), or Cl(V) was considered.     

Crystal structure of Li(H<Subscript>2</Subscript>O)<Subscript>3</Subscript>[GaEdta]

The ethylenediaminetetraacetate complex Li(H₂O)₃[Ga(Edta)] was synthesized and its crystal structure composed of octahedral (Ga(Edta)⁻ anions connected to the Li(H₂O)₃⁺ ion through the oxygen atom was studied. Five of the six hydrogen atoms of water molecules are involved in weak hydrogen bonds with the oxygen atoms of four Ga(Edta)⁻ complexes, the complex anion is hydrogen-bonded to five water molecules. In addition, shortened contacts C(221)–H(22A)…O(112) between the Ga(Edta)⁻ anions were found. As a result, the molecular packing in the crystal is determined by the three-dimensional lace of hydrogen bonds. The results are compared with published data for the lithium salts of Bi(III), Sb(III), Fe(III), Ni(II), and Hg(II) ethylenediaminetetraacetates.     

New uranyl complex with imidazolidine-2-one [UO<Subscript>2</Subscript>(Imon)<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>: Structure and some properties

A complex of uranyl perchlorate with imidazolidine-2-one as the molecular ligand, [UO₂(Imon)₄(H₂O)](ClO₄)₂ (I), was synthesized and structurally characterized by X-ray diffraction analysis. The coordination number of the uranium atom is 7. The nearest environment of the uranyl ion includes four O atoms of the imidazolidine-2-one molecules and one O atom of the water molecule. The perchlorate anions are outer-sphere ligands. The crystals are monoclinic: space group P2₁/c; a = 16.294(3) Å, b = 16.135(3) Å, c = 9.987(2) Å, = 97.69 (3)°, V = 2603.0 (9) ų, (calcd) = 2.117 g/cm³, Z = 4. The IR and luminescence spectra of the complex were recorded.Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 919–924.Original Russian Text Copyright © 2004 by Andreev, Antipin, Budantseva, Tuchina, Serezhkina, Fedoseev, Yusov.     

Crystal structure of Ba(VUO<Subscript>6</Subscript>)<Subscript>2</Subscript>

The crystal structure of Ba(VUO₆)₂ was determined by X-ray diffraction at 243 K: monoclinic crystal system, space group P2₁/c, unit cell parameters a=6.4992(6) Å, b=8.3803(8) Å, c=10.4235(9) Å, =104.749(2) °, Z=2. The structure contains close-packed [VUO₆] ₂ ^- layers formed by the dimers of the flattened U₂O₁₂ pentagonal bipyramids and by the dimers of V₂O₈ square pyramids. The neighboring layers are bound by the statistically distributed barium atoms.Original Russian Text Copyright © 2004 by E. V. Alekseev, E. V. Suleimanov, E. V. Chuprunov, and G. K. FukinTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 544–548, May–June 2004.     

Low-dimensional compounds containing cyano groups. IX. Preparation,structure and properties of the [Cu(bpy)<Subscript>2</Subscript>(dca)]CF<Subscript>3</Subscript>SO<Subscript>3</Subscript> complex

The ionic [Cu(C₂N₃)(C₁₀H₈N₂)₂](CF₃SO₃) compound, which contains two crystallographic independent formula units, is formed by [Cu(bpy)₂(dca)]⁺ complex cations (bpy=2,2-bipyridine, dca=dicyanamide) and uncoordinated CF₃SO ₃ ^– anions, which are in a staggered conformation. The shapes of coordination polyhedra around both copper atoms, which are fivefold coordinated by two bpy molecules and one dca ligand monodentately coordinated through a cyano N atom in the equatorial plane at a distance of 2.001(3)Å for the first and 1.988(4)Å for the second polyhedron, are distorted trigonal bipyramids. Besides the ionic forces the structure is stabilized by weak C–H...O hydrogen bonds and possible – interactions between pyridine rings of bpy molecules. Along with the structural-spectral correlation we discuss the thermal decomposition of the title complex.     

Coordination Polyhedra TiOn in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of 532 compounds containing 940 crystallographic sorts of titanium atoms in TiO _n coordination polyhedra. It was found that Ti(IV) or Ti(III) atoms can coordinate four to eight oxygen atoms. For a constant valence state and a constant coordination number (C.N.) of titanium, the Ti–O bond lengths vary by 0.1–1.0 Å. At C.N. #gt; 5, the volume of the metal VDP remains virtually unchanged; when the C.N. decreases to 4, the VDP volume increases by 2–3 ų. For a constant C.N., Ti(IV) Ti(III) transition is accompanied by an increase in the VDP volume of metal atoms of 0.5–1.9 ų. The VDP characteristics of the Ti atoms can be used to determine their valence state and to identify the titanium–metal bonds in the structures of compounds.     

Crystal structure of fluorosulfate complex compounds of indium(III) M<Subscript>2</Subscript>[InF<Subscript>3</Subscript>(SO<Subscript>4</Subscript>)H<Subscript>2</Subscript>O] (M = K,NH<Subscript>4</Subscript>)

The crystal structures of isostructural mixed-ligand fluorosulfate complex compounds of indium(III) M₂[InF₃(SO₄)H₂O] (M = K, NH₄), formed of K⁺ cations, NH₄ ⁺ respectively, and complex [InF₃(SO₄)H₂O]^2– anions are determined. In the complex anion, the indium atom surrounded by three F atoms, the oxygen atom of the coordinated H₂O molecule, and two oxygen atoms of the bridging sulfate group forms a slightly distorted octahedron (CN 6). Via alternating bridging SO₄ groups, the polyhedra of In(III) atoms are arranged in polymer chains. The O–H???F hydrogen bonds organize the chains in a three-dimensional network. The K⁺ and NH₄ ⁺ cations are located in the structure framework and additionally strengthen it.     

A Strong Luminescent Quaternary Dimeric Complex [Tb(BAA)<Subscript>2</Subscript>(Phen)(NO<Subscript>3</Subscript>)]<Subscript>2</Subscript>: Hydrothermal Synthesis,Structure, and Photophysics

In terms of the molecular fragment principle, a quaternary complex is assembled under hydrothermal conditions and characterized as [Tb(BAA)₂(Phen)(NO₃)]₂ (BAA is benzoyl acetic acid, Phen is 1,10- phenanthroline) by elementary analysis and IR, UV, fluorescence excitation, and emission spectra. The X-ray single-crystal diffraction data indicate that the title complex crystallizes in triclinic system, space group , with unit cell parameters a = 8.953(6), b = 13.332(9), c = 13.431(9) Å, α = 60.669(7)°, β = 89.649(8)°, γ = 72.068(9)°, V = 1309.3(15) ų, ρ(calcd) = ∼ 1.703 g/cm³, Z = 1 (per dimeric unit), F(000) = 664, GOOF = 1.071, R ₁ = 0.0627. The terbium complex forms a dimer with a coordination number of nine in which each pair of adjacent terbium ions is bridged by four BAA groups via two types of coordination modes. The dimer exhibits strong green luminescence of Tb³⁺.__________From Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 472–478.Original English Text Copyright © 2005 by Bai, Yan, Chen.     

Coordination Polyhedra LnO<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (Ln = Tb,Dy, Ho) in Crystal Structures

The Voronoi-Dirichlet polyhedra (VDP) were used to study the stereochemical features of terbium, dysprosium, and holmium surrounded by oxygen in the structures of 456 compounds. The Tb, Dy, and Ho atoms have C.N.s of 6 to 12 with respect to oxygen. The volume of the VDP of lanthanide atoms does not depend on their C.N. or the shape of the coordination polyhedron, although the Ln(III)-O bond length changes by 0.6–0.7 Å. The Tb(III) → Tb(IV) transition is accompanied by a decrease in the terbium VDP volume by ～2 ų.     

Photochemical reactions of <Emphasis Type="Italic">cis</Emphasis>-[(η<Superscript>4</Superscript>-NBD)M(CO)<Subscript>4</Subscript>] (NBD = norbornadiene; M = Cr,Mo) olefin complex with ligand,containing S and N donor atoms

New complexes cis-[M(CO)₄-DABRd] (M = Cr(I), Mo(II) and fac-[M(CO)₃-SAT] (M = Cr(III), Mo(IV)) have been synthesized by the photochemical reactions of cis-[(η⁴-NBD)M(CO)₄] (NBD is norbornadiene; M=Cr, Mo) with 5-(4-dimethylaminobenzylidene) rhodanine (DABRd) and salicylidene-3-amino-1,2,4-triazole (SAT) ligands and characterized by elemental analysis, FT-IR and ¹H NMR spectroscopy, and mass spectrometry. The spectroscopic studies show that the DABRd ligand acts as a bidentate ligand coordinating via both NH-(S)C=S sulfur donor atoms in I and II and SAT ligand behaves as a tridentate ligand coordinating via its all imine nitrogen-C=N-donor atoms in III and IV to the metal center. The article was submitted by the authors in English.     

Structure and real composition of undoped and Cr- and Ni-doped Sr<Subscript>0.61</Subscript>Ba<Subscript>0.39</Subscript>Nb<Subscript>2</Subscript>O<Subscript>6</Subscript> single crystals

Strontium barium niobate crystals with congruent melting composition Sr_0.61Ba_0.39Nb₂O₆ (SBN-61), both nominally pure and doped with Cr³⁺ и Ni³⁺ ions, have been investigated by neutron diffraction. Different strontium and barium contents as well as their different distribution over the Sr1, of Sr2 and Ba2 crystallographic sites of SBN-61 structure, caused by introduction of dopants, have been revealed. Coordination polyhedra of cations have been established based on the analysis of cation–anion internuclear distances together with the calculation of bond-valence sums for cations, which are equal to their formal charge. It was found that the Nb1 and Nb2 atoms are located in distorted octahedra with quadfurcated (the Nb1O₆ polyhedron) or bifurcated (the Nb2O₆ polyhedron) vertices, and the Sr1 atoms are located in a cuboctahedron with bifurcated vertices in the base plane. Different polyhedra have been revealed for the Sr2 and Ba2 atoms: Sr2 atoms are coordinated by 15 oxygen atoms to form a highly distorted five-capped pentagonal prism, whereas Ba2 atoms are located in a highly distorted three-capped trigonal prism with a coordination number 9. Comparison of interatomic and internuclear distances, determined by X-ray and neutron diffraction analyses, respectively, allowed to reveal a highly pronounced shift of electron density in Nb1 and Sr2 polyhedra, responsible for the covalent bond and properties of crystals. Location of Cr³⁺ и Ni³⁺ dopant ions in the SBN-61 structure as well as their formal charges has been discussed.     

Crystal structure of new ammonium fluoroindate(III) (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>[InF<Subscript>5</Subscript>]

A new indium(III) fluoride complex with the ammonium cation (NH₄)₂[InF₅] is synthesized and its crystal structure is studied. The structure of (NH₄)₂[InF₅] is formed of NH₄ ⁺ cations and complex [InF₅]^2– anions. The In atom in the complex anion surrounded by four terminal and two bridging F atoms forms an almost regular octahedral coordination polyhedron (CN 6) with two terminal F atoms in the axial positions and two terminal and two bridging F atoms in the equatorial plane. Through bridging F atoms, the InF6 polyhedra are arranged in polymer trans- vertex-connected corrugated anion chains (InF₅) _n ^2n? directed along the c axis. The N–H?F hydrogen bonds organize the chains in a three-dimensional framework.     

Crystal Structure of Sodium Perchloratotriacetatoneptunate(V) Monohydrate Na<Subscript>3</Subscript>NpO<Subscript>2</Subscript>(OOCCH<Subscript>3</Subscript>)<Subscript>3</Subscript>ClO<Subscript>4</Subscript> · H<Subscript>2</Subscript>O

The crystal structure of Na₃NpO₂(OOCCH₃)₃ClO₄ · H₂O was studied by single-crystal X-ray diffraction method. The structure is composed of the complex anions NpO₂(OOCCH₃)₃]²⁻, perchlorate anions, Na cations, and water molecules. The oxygen environment of Np(V) is a hexagonal bipyramid whose equatorial plane is formed by the oxygen atoms of three acetate ions. In addition to the acetate anions, the structure contains the perchlorate ion whose oxygen atoms, except for one, are included in the coordination environment of Na⁺ cations.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 636–640.Original Russian Text Copyright © 2005 by Charushnikova, Fedoseev, Starikova.     

Complexation processes in KF-SbF<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system studied by calorimetric titration

Complexation in a KF-SbF₃-H₂O system is studied in a range of molar ratios of fluorides KF : SbF₃= (0.1–2) : 1 by calorimetric titration. The equilibrium formation constants of complexes KSb₂F₇, KSbF₄, and K₂SbF₅ (5.8×10⁵±800, 3.3×10⁴±500, and 1.9×10⁶± 950, respectively) and the changes in enthalpy (–31.75± 0.74, –28.15±0.44, and –25.5±0.64 J mol^–1, respectively) and entropy (4±7, –8±5, and –35±9 J mol^–1 K^–1, respectively) are determined. The thermodynamic stability of the antimony(III) fluoride complexes is found to increase on going from KSb₂F₇ to K₂SbF₅.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 168–171.Original Russian Text Copyright © 2005 by Kovaleva, Zemnukhova, Lebedeva, Fedorishcheva.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Electrochemical Synthesis of Co-intercalation Compounds in the Graphite-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-H<Subscript>3</Subscript>PO<Subscript>4</Subscript>System

Anodic oxidation of highly oriented pyrolytic graphite in an electrolyte containing concentrated sulfuric and anhydrous phosphoric acids is studied for the first time. The synthesis was carried out under galvanostatic conditions at a current I = 0.5 mA and an elevated temperature (t = 80°C). Intercalation compounds of graphite (ICG) are shown to form at all concentration ratios of H₂SO₄ and H³PO⁴ acids. The intercalation compound of step I forms in solutions containing more than 80 wt % H₂SO₄, a mixture of compounds of intercalation steps I and II forms in 60% H²SO⁴, intercalation step II is realized in the sulfuric acid concentration range from 10 to 40%, and a mixture of compounds of intercalation steps III and II is formed in 5% H₂SO₄ solutions. The threshold concentration of H₂SO₄ intercalation is ∼2%. With the decrease in active intercalate (H₂SO₄) concentration, the charging curves are gradually smoothed, the intercalation step number increases, and the potentials of ICG formation also increase. As the sulfuric acid concentration in the electrolyte changes from 96 to 40 wt %, the filled-layer thickness d _i in ICG monotonously increases from 0.803 to 0.820 nm, which apparently is associated with the greater size of phosphoric acid molecules. With further increase in H₃PO₄ concentration in solution, d _i remains unchanged. According to the results of chemical analysis, both acids are simultaneously incorporated into the graphite interplanar spacing and their ratio in ICG is determined by the electrolyte composition.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 651–655.Original Russian Text Copyright © 2005 by Leshin, Sorokina, Avdeev.     

Mononuclear manganese(II) and manganese(III) complexes of N<Subscript>2</Subscript>O donors involving amine and phenolate ligands: absorption spectra,electrochemistry and crystal structure of [Mn(L<Subscript>3</Subscript>)<Subscript>2</Subscript>](ClO<Subscript>4</Subscript>)

A number of mononuclear manganese(II) and manganese(III) complexes have been synthesized from tridentate N₂O aminophenol ligands (HL₁–HL₅) formed by reduction of corresponding Schiff bases with NaBH₄. Three types of tridentate N₂O aminophenols have been prepared by reducing with NaBH₄which are (a) Schiff bases obtained by bromo salicylaldehyde reaction with N,N-dimethyl/N,N-diethyl ethylene diamine (HL₁, HL₂), (b) Schiff bases obtained by condensing salicylaldehyde/bromo salicylaldehyde and picolyl amine (HL₃, HL₄), (c) pyridine-2-aldehyde and 2-aminophenol (HL₅). All the manganese complexes have been prepared by direct addition of manganese perchlorate to the corresponding ligands and were characterized by the combination of i.r., u.v.–vis spectroscopy, magnetic moments and electrochemical studies. The u.v.–vis spectra of all of the manganese(III) complexes show two weak d–d transitions in the 630–520 nm region, which support a distorted octahedral geometry. The electron transfer properties of all of the manganese(III) complexes (1–4 and 6) exhibit mostly similar characteristics consisting two redox couples corresponding to the Mn^III → Mn^II reductions and Mn^III → Mn^IV oxidations. The electronic effect on the potential has also been studied by changing different substituents in the ligands. In all cases, an electron-donating group stabilizes the higher oxidation state and electron withdrawing group prefers the lower oxidation state. The cyclic voltammogram of [Mn^II(L₅)₂] shows an irreversible oxidation Mn^II → Mn^III at −0.88 V, followed by another quasi-reversible oxidation Mn^III → Mn^IV at +0.48 V. The manganese(III) complex (3) [Mn(L₃)₂]ClO₄has been characterized by X-ray crystallography.     

A Chiral Coordination Polymer of Silver(I) with Saccharinate and Pyridine: Synthesis,Spectral, Thermal,and Structural Characterization of [Ag(sac)(py)]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

The first silver(I) complex of saccharinate (sac) with pyridine (py), [Ag(sac)(py)]_n has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffractometry. The complex crystallizes in chiral, trigonal space group P3₁21 (No. 152) with unit cell parameters of a = 11.2605(2) Å, c = 17.3300(4) Å, V = 1903.02(6) ų and Z = 6. [Ag(sac)(py)]_n contains monomeric [Ag(sac)(py)] units linked into infinite helices by way of Ag⋅sAg interactions [d(Ag⋅sAg) = 2.909(2) and 2.985(1) Å]. The distorted square-planar environment of Ag is completed by an N-bonded sac [Ag—N = 2.084(2) Å] and a py molecule [Ag—N = 2.116(2) Å]. The N_sac—Ag—N_py angle is 173.85(10)^∘. The one-dimensional chains are crosslinked by C—H⋅sO interactions involving the carbonyl and sulfonyl O atoms of sac and aromatic-ring hydrogen atoms of both sac and py. The thermal stability of the title complex was investigated using thermogravimetry and differential thermal analysis in a static atmosphere of air. The first decomposition stage between 90 and 160^∘C corresponds to removal of the py molecule in a single stage, while the degradation of the sac moiety occurs at two stages in the temperature range 370–515^∘C, giving an end product of metallic Ag.     

<Emphasis Type="Italic">In situ</Emphasis> IR Spectroscopic and XPS Study of Surface Complexes and Their Transformations during Ammonia Oxidation to Nitrous Oxide over an Mn-Bi-O/α-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalyst

Surface complexes resulting from the interaction between ammonia and a manganese-bismuth oxide catalyst were studied by IR spectroscopy and XPS. At the first stage, ammonia reacts with the catalyst to form the surface complexes [NH] and [NH₂] via abstraction of hydrogen atoms even at room temperature. Bringing the catalyst into contact with flowing air at room temperature or with helium under heating results in further hydrogen abstraction and simultaneous formation of [N] from [NH₂] and [NH]. The nitrogen atoms are localized on both reduced (Mn²⁺) and oxidized (Mn^δ+, 2 < δ < 3) sites. Atomic nitrogen is highly mobile and reacts readily with the weakly bound oxygen of the oxidized (Mn^δ+-N) active site. The nitrogen atoms localized on oxidized sites play the key role in N₂O formation. Nitrous oxide is readily formed through the interaction between two Mn^δ+-N species. N₂ molecules result from the recombination of nitrogen atoms localized on reduced (Mn²⁺-N) sites.__________Translated from Kinetika i Kataliz, Vol. 46, No. 4, 2005, pp. 590–600.Original Russian Text Copyright © 2005 by Slavinskaya, Chesalov, Boronin, Polukhina, Noskov.