Synthesis and physicochemical study of M<Subscript>4</Subscript>Na<Subscript>2</Subscript>V<Subscript>10</Subscript>O<Subscript>28</Subscript> · 10H<Subscript>2</Subscript>O (M=K,Rb, NH<Subscript>4</Subscript>)

The formation conditions and physicochemical properties of binary decavanadates M₄Na₂V₁₀O₂₈ · 10H₂O (M=K, Rb, NH₄), synthesized by crystallization from saturated solutions of the NaVO₃-MH₂AsO₄-H₂O systems, were studied by chemical analysis, X-ray powder diffraction, microscopy, thermogravimetry, and IR spectroscopy. To optimize the synthesis conditions of M₄Na₂V₁₀O₂₈ · 10H₂O, the ( 1-x)NaVO₃ · 2H₂O · xMH2AsO4-H₂O (0.2 ≤ x ≤ 0.8) isomolar series method was applied to studying the interaction in the NaVO₃-MH₂AsO₄-H₂O systems (M = K, Rb, Cs) at the 0.4 mol/L total molar concentration of NaVO₃ and MH₂AsO₄ in solutions. The studied M₄Na₂V₁₀O₂₈ · 10H₂O compounds were shown to be isostructural with triclinic crystals (Z= 1, space group P $ \bar 1 $ \bar 1 ), and their unit cell parameters were estimated.     

Crystal structure and vibrational spectra of M[VO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]·H<Subscript>2</Subscript>O (M = K,Rb, NH<Subscript>4</Subscript>)

By the hydration of MVO(SeO₄)₂ with saturated water vapors at room temperature a series of isostructural complex compounds of vanadium(V) of the composition M[VO₂(SeO₄)(H₂O)₂]·H₂O (K, Rb, NH₄) are synthesized and their physicochemical properties are studied. Based on the X-ray and neutron diffraction data, it is found that their crystal structure is composed of VO₆ octahedra linked in infinite chains by bridging SeO₄ tetrahedra. Each of the VO₆ octahedra has two short terminal V-O bonds forming a bent dioxovanadium group VO₂⁺. Two water molecules are coordinated by vanadium and one molecule is out of the first coordination sphere in the interchain space. The vibrational spectra of the studied compounds are completely consistent with their structural features.     

Cuboidal cluster aqua complexes with {M<Subscript>3</Subscript>M′Q<Subscript>4</Subscript>} cores (M = Mo,W; M′ = Ni,Pd; Q = S,Se) and their derivatives

The results of the studies on the synthesis, structure, and reactivity of heterometal cuboidal clusters of Mo and W, {M₃M′(μ₋₃Q)₄}⁴⁺ (M = Mo, W; Q = S, Se; M′ = Ni, Pd), published in the last decade by the authors, have been summarized.     

Synthesis and structure of M[UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)(NCS)] · 0.5H<Subscript>2</Subscript>O (M = Rb or Cs)

Single crystals of M[UO₂(C₂O₄)(NCS)] · 0.5H₂O (M = Rb (I) or Cs (II)) have been synthesized and studied by X-ray diffraction analysis. The compounds are isostructural, and their crystals are monoclinic with the space group C2/c, Z = 4, and unit cell parameters: a = 9.0624(5) Å, b = 13.1242(7) Å, c = 8.9204(5) Å, β = 98.897(2)°, R = 0.0226 (I); a = 9.3171(3) Å, b = 13.2987(5) Å, c = 9.1151(3) Å, β = 101.0860(10)°, R = 0.0214 (II). The main structural units of the crystals of I and II are the [[UO₂(C₂O₄)(NCS)]^? chains belonging to the crystal-chemical group AK⁰²M¹ (A = UO ₂ ²⁺ , K⁰² = C₂O ₄ ^2? , M¹ = NCS^? of the uranyl complexes. The uranium-containing chains are joined into a three-dimensional framework through electrostatic interactions with the outer-sphere cations and hydrogen bonds involving the water molecules.     

Unusual formation reaction of 2′-(methyl)-3′-acetyl-1,9-dihydro(4′,5′-dihydrofurano) [60]fullerene in reaction of C<Subscript>60</Subscript> with complexes VO(acac)<Subscript>2</Subscript> and MoO<Subscript>2</Subscript>(acac)<Subscript>2</Subscript>

A preparation method was developed for 2′-(methyl)-3′-acetyl-1,9-dihydro(4′,5′-dihydrofurano) [60]fullerene based on the liquid phase oxidation of C₆₀ using VO(acac)₂ and MoO₂(acac)₂.     

Synthesis and crystal structure of two {M(4,4′-dpdo)<Subscript>2</Subscript>[N(CN)<Subscript>2</Subscript>]<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>} complexes (M = Co(II), Mn(II); 4,4′-dpdo = 4,4′-bipyridyl-N,N′-dioxide)

The ligand 4,4′-bipyridyl-N,N′-dioxide (4,4′-dpdo) was used in the synthesis of two complexes, {Co(4,4′-dpdo)₂[N(CN)₂]₂(H₂O)₂} (1) and {Mn(4,4′-dpdo)₂[N(CN)₂]₂(H₂O)₂} (2). The complexes were found to be isostructural, triclinic, space group P-1 with Z = 1 and the following unit cell parameters: a = 8.158(8) Å, b = 8.865(8) Å, c = 9.477(9) Å; α = 70.988(13)°, β = 78.778(13)°, γ = 71.964(10)°; V = 612.8(10) ų for 1; a = 8.247(14) Å, b = 9.001(16) Å, c = 9.707(17) Å; α = 71.02(2)°, β = 78.63(2)°, γ = 72.62(2)°; V = 646(2) ų for 2. Final R-values were 0.075 and 0.083 for 1 and 2, respectively. In the molecules of the complexes, Co(II) or Mn(II) cation is coordinated by two O-atoms of two 4,4′-dpdo ligands, two terminal N-atoms of two dicyanamides, and two O-atoms of water molecules. The crystals are molecular, with adjacent complex molecules linked through a system of O-H...N and O-H...O hydrogen bonds.     

Study of the fluorite–pyrochlore–fluorite phase transitions in Ln<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript> (Ln=Lu,Yb, Tm)

The ordering processes in Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) are studied by X-ray diffraction, thermal analysis, infrared absorption (IR) spectroscopy, and electrical conductivity measurements. The coprecipitation method followed by freeze-drying was used for Ln₂Ti₂O₇ synthesis. The region of low-temperature fluorite phase existence is 600 °C<T<740 °C. The low-temperature fluorite–pyrochlore phase transition in Ln₂Ti₂O₇ takes place at ~740–800 °C. Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) have the structure of disordered pyrochlore with antisite Ln–Ti defects at 800 °C<T<1,100 °C.The high-temperature pyrochlore–fluorite transformation takes place in Tm₂Ti₂O₇, Yb₂Ti₂O₇, and Lu₂Ti₂O₇ in air at T>1,600 °C. The conductivity values are 5·10^–3 S/cm for Tm₂Ti₂O₇, 6·10^–3 S/cm for Yb₂Ti₂O₇, and 10^–2 S/cm for Lu₂Ti₂O₇ at 740 °C. This order–disorder transition leads to a 2 orders of magnitude conductivity growth and a 10–30 times permittivity increase in Ln₂Ti₂O₇ samples obtained at 1,700 °C.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

Synthesis and structure of trinuclear pyrazolate-bridged acetates M<Subscript>3</Subscript>(μ-dmpz)<Subscript>4</Subscript>(Hdmpz)<Subscript>2</Subscript>(OOCMe)<Subscript>2</Subscript> (M = Zn or Co; Hdmpz = 3,5-dimethylpyrazole)

We discovered that reactions of hydrous cobalt and zinc acetates with 3,5-dimethylpyrazole (Hdmpz) in boiling xylene or toluene or upon the thermolysis of solid precursors (150°C) yield trinuclear pyrazolate-bridged complexes M₃ (μ-dmpz)₄(Hdmpz)₂ (OOCMe)₂(M = Zn or Co). Depending on the crystallization conditions, these complexes contain various solvating molecules (benzene, toluene, or Hdmpz), which influences the character of intramolecular and intermolecular hydrogen bonding, as shown by X-ray crystallography.     

Exploring the Reactivity of Rh<Subscript>2</Subscript> (OAc)<Subscript>4</Subscript> with 2, 2′ -Dipyridylamine

A series of three new compounds obtained from the reaction of Rh₂(OAc)₄ and 2, 2 -dipyridylamine (Hdpa) under various conditions have been characterized. All are diamagnetic and have a Rh–Rh single bond. In Rh₂(dpa)₄, 1, there are four bridging dpa anions which bind the two Rh atoms through one pyridyl N atom and one amido N atom though two of these ligands interact further with a rhodium atom through the third N atom. In the other two compounds the Hdpa ligand is neutral. Thus Rh₂(OAc)₄(Hdpa)₂, 2, is an adduct of the well known complex dirhodium tetraacetate in which the two Hdpa ligands occupy axial positions. In the third compound, Rh₂(Hdpa)₂(OAc)₂Cl₂, 3, only two acetate bridges are present. One Hdpa molecule chelates equatorially each rhodium atom and the chloride ions are axially coordinated. The Rh–Rh distances are 2. 4005(6) and 2. 4042(8) Å for 1 and 2, respectively. For 3, the Rh–Rh distance of 2. 593(1) Å is significantly longer than those in 1 and 2 because of the presence of fewer bridging ligands.     

Structural features of phases (Na<Subscript>0.5</Subscript>R<Subscript>0.5</Subscript>)MO<Subscript>4</Subscript> and (Na<Subscript>0.5</Subscript>R<Subscript>0.5</Subscript>)MO<Subscript>4</Subscript>:R′ (R = Gd,La; R′ = Er,Tm, Yb; M = W,Mo) of the scheelite family

The structural data for single crystals of (Na_0.5R_0.5)MO₄ and (Na_0.5R_0.5)MO₄:R′ (R = La, Gd; R′ = Er, Tm, Yb; M = W, Mo) grown by the Czochralski method were studied by X-ray diffraction and analyzed. The structural characteristics of these compounds depend on the sort of cations M and R. The formation of superstructures was found in the scheelite structure, and distortion of the scheelite structure depending on the composition and preparation conditions was established (with unit cell rotation by 45° and triclinic distortion of the scheelite structure for (Na_0.5Gd_0.5)WO₄:Tm, with doubled unit cell compared to the scheelite type structure for (Na_0.5Gd_0.5)WO₄ and (Na_0.5Gd_0.5)WO₄:Yb). In the case of overstoichiometric oxygen content in the crystal, the unit cell symmetry increases to space group I4₁/amd or (Na_0.5Gd_0.5)WO₄:Yb without considerable change in the cell parameters. On the basis of experimental data, a transformation scheme for the structures in the system Na ₂ ⁺ M⁶⁺O_4?-“R³⁺M⁵⁺O₄” was proposed.     

[H<Subscript>4</Subscript>(4,4′-Bipy)<Subscript>3</Subscript>][Sc(OH)(H<Subscript>2</Subscript>O)<Subscript>5</Subscript>]<Subscript>2</Subscript>Cl<Subscript>8</Subscript>: Synthesis,structure, and solid-phase thermal transformation

The reaction of [Sc(OH)(H₂O)₅]₂Cl₄ · 2H₂O in isopropanol with 4,4′-Bipy in CHCl₃ produced a crystalline compound, which was identified as [H₄(4,4′-Bipy)₃][Sc(OH)(H₂O)₅]₂Cl₈ (I) by elemental analysis, IR spectra, and single-crystal X-ray diffraction. In the structure of compound I, the three protonated diimine molecules form a centrosymmetric trimer via N...N hydrogen bonds. The polyhedron around the Sc atom is an octahedron with one split vertex. The excursion of the Sc atom from the plane formed by the oxygen atoms (water molecules) toward the hydroxo bridges is 0.5 Å. The thermolysis of compound I generates ScCl₃, whereas the final decomposition product of the precursor dimer is ScOCl.     

Crystal structures of chiral (R/S) (C<Subscript>8</Subscript>H<Subscript>11</Subscript>N)<Subscript>2</Subscript> · Zn(OAc)<Subscript>2</Subscript>

Two opposite configuration (R/S) of chiral complexes (C₈H₁₁N)₂ · Zn(OAc)₂ (Ia and Ib—L-(−)-) and D-(+)-isomer) were synthesized by a simple one-pot method. The crystal structures of Ia and ib determined by X-ray crystallography.     

Pyrazolate-bridged binuclear zinc complexes Zn<Subscript>2</Subscript>(μ-dmpz)<Subscript>2</Subscript>(Hdmpz)<Subscript>2</Subscript>(OOCR)<Subscript>2</Subscript> (R = Me,Ph; Hdmpz = 3,5-dimethylpyrazole)

Triethylamine reacts with aqueous zinc acetate and the product of its thermolysis in the presence of benzoic acid to yield the complexes [Zn₇(μ₄-O)(μ-OOCMe)₁₀][η-OC(Me)OHNEt₃]₂ (1) and [Zn₂(μOOCPh)₄][η-OC(Me)OHNEt₃]₂ (2), respectively. The reactions of 1 and 2 with 3,5-dimethylpyrazole at room temperature in benzene yield pyrazolate-bridged binuclear complexes Zn₂(μdmpz)₂(Hdmpz)₂(OOCR)₂ (R = Me (3), Ph (4)). The structures of complexes 1–4 have been determined by X-ray crystallography.     

Geometric and electronic structure of an N,N′-ethylene-bis(salicylaldiminato) zinc(II) molecule,ZnO<Subscript>2</Subscript>N<Subscript>2</Subscript>C<Subscript>16</Subscript>H<Subscript>14</Subscript>

Gas electron diffraction at a temperature T of 641(5) K is used to study the structure of an N,N′-ethylenebis(salicylaldiminato) zinc(II) molecule, ZnO₂N₂C₁₆H₁₄, further Zn(salen). The structure of a gaseous Zn(salen) complex has C ₂ symmetry and is characterized by a substantial turn of two chelating fragments of the ligand with respect to each other, and also by a big difference in the length of coordination bonds: r _h1(Zn-O)=1.902(7) Å r _h1(Zn-N)= 2.027(7) Å. Results of the DFT/B3LYP calculation with 6-31G* and CEP,TZV basis sets of the molecule structure well agree with the experimental data. The electronic structure of Ni(salen), Cu(salen), Zn(salen), and Zn(acacen) molecules is considered.     

Synthesis of dicationic μ-diborolyl triple-decker complexes [CpCo(μ-1,3-C<Subscript>3</Subscript>B<Subscript>2</Subscript>Me<Subscript>5</Subscript>)M(C<Subscript>6</Subscript>H<Subscript>6</Subscript>)]<Superscript>2+</Superscript> (M = Rh,Ir)

Dicationic triple-decker complexes [CpCo(μ-1,3-C₃B₂Me₅)M(C₆H₆)]²⁺ (M = Rh (3), Ir (4)) were synthesized by the reaction of [CpCo(μ-C₃B₂Me₅)MBr₂]₂ (M = Rh, Ir) with benzene in the presence of AgBF₄. The structure of 3(BF₄)₂ was determined by X-ray diffraction analysis.     

Synthesis and crystal structure of a 1D coordination polymer Cu<Subscript>3</Subscript>(Mip)<Subscript>4</Subscript>(2,2′-Bipy)<Subscript>2</Subscript> (H<Subscript>2</Subscript>Mip = 5-methylisophthalic acid, 2,2′-Bipy = 2,2′-bipyridine)

A new metal-organic coordination polymer Cu₃(Mip)₄(2,2′-Bipy)₂ (I), where H₂Mip = 5-methylisophthalic acid, 2,2′-Bipy = 2,2′-bipyridine has been hydrothermally synthesized and characterized by IR, elemental analysis, single-crystal X-ray diffraction analysis, and powder X-ray diffraction. The X-ray diffraction analysis reveals that I crystallizes in the triclinic crystal system, space group P \(\bar 1\) and exhibits a one-dimensional chain structure, which contains a trinuclear [Cu₃(Mip)₂(HMip)₂(2,2′-Bipy)₂] subunit, and the adjacent subunits are bridged by Mip anions into a 1D chain. Unit cell parameters for I: a = 10.239(2), b = 11.249(2), c = 11.971(2) Å, α = 82.01(1)°, β = 65.03(2)°, γ = 84.32(2)°, V = 1236.5(4) ų, Z = 2.     

Clathrate [Zn(C<Subscript>6</Subscript>H<Subscript>5</Subscript>COO)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · 2CH<Subscript>3</Subscript>COOH: Synthesis and crystal structure

The clathrate [Zn(C₆H₅COO)₂(H₂O)₂] · 2CH₃COOH (I) was obtained for the first time from zinc(II) benzoate. The individuality, the unit cell parameters, and the number of “guest” molecules in complex I were determined from X-ray diffraction and derivatographic data. Its crystal structure was solved.     

Crystal structure and thermal properties of [Au(en)<Subscript>2</Subscript>]<Subscript>2</Subscript>[Cu(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>]<Subscript>3</Subscript>·8H<Subscript>2</Subscript>O

The crystal structure of a double complex salt of the composition [Au(en)₂]₂[Cu(C₂O₄)₂]₃·8H₂O (en = ethylenediamine) at 150 K is determined by single crystal X-ray diffraction. The crystal data for C₂₀H₄₈Au₂Cu₃N₈O₃₂ are: a = 9.1761(3) Å, b = 16.9749(6) Å, c = 13.4475(5) Å, β = 104.333(1)°, V = 2029.43(12) ų, P2₁/c space group, Z = 2, d _x = 2.450 g/cm³. It is demonstrated that the thermal decomposition of the double complex salt in a helium or hydrogen atmosphere affords the solid solution Au_0.4Cu_0.6.     

Direct synthesis of hydrogen peroxide from hydrogen and oxygen over insoluble Pd<Subscript>0.15</Subscript>M<Subscript>2.5</Subscript>H<Subscript>0.2</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> (M = K,Rb, and Cs) heteropolyacid catalysts

Palladium-containing insoluble heteropolyacid (HPA) catalysts (Pd_0.15M_2.5H_0.2PW₁₂O₄₀) were prepared by an ion-exchange method using various alkaline metal ions (M = K⁺, Rb⁺, and Cs⁺) (denoted as Pd-KPW, Pd-RbPW, and Pd-CsPW). They were then applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. Conversion of hydrogen over the catalysts was almost identical with no great difference, while selectivity for hydrogen peroxide increased in the order of Pd-KPW < Pd-RbPW < Pd-CsPW. As a consequence, yield for hydrogen peroxide increased in the order of Pd-KPW < Pd-RbPW < Pd-CsPW. It was found that yield for hydrogen peroxide increased with increasing Pd 3d_5/2 binding energy of the catalyst. Among the catalysts tested, Pd-CsPW catalyst with the highest Pd 3d_5/2 binding energy showed the highest yield for hydrogen peroxide.     

Synthesis and structures of cationic μ-diborolyl triple-decker complexes [CpCo(1,3-C<Subscript>3</Subscript>B<Subscript>2</Subscript>Me<Subscript>5</Subscript>)M(C<Subscript>5</Subscript>R<Subscript>5</Subscript>)]<Superscript>+</Superscript> (M = Rh or Ir)

The cationic triple-decker complexes [CpCo(1,3-C₃B₂Me₅)M(C₅R₅)]⁺ (M = Rh (2), Ir (3), R = H (a), Me (b)) with the bridging diborolyl ligand were synthesized by the reaction of the sandwich anion [CpCo(1,3-C₃B₂Me₅)]^- (1) with the halide complexes [CpMI₂]₂ or [Cp^*MCl₂]₂ (Cp^* = C₅Me₅). The structures of [2b]PF₆ and [3b]PF₆ were established by X-ray diffraction. The nature of the metal—diborolyl bond in these complexes was analyzed using the energy decomposition scheme.