Co3O4−CeO2 Nanocomposites for Low-Temperature CO Oxidation

In an effort to combine the favorable catalytic properties of Co₃O₄ and CeO₂, nanocomposites with different phase distribution and Co₃O₄ loading were prepared and employed for CO oxidation. Synthesizing Co₃O₄-modified CeO₂ via three different sol-gel based routes, each with 10.4 wt % Co₃O₄ loading, yielded three different nanocomposite morphologies: CeO₂-supported Co₃O₄ layers, intermixed oxides, and homogeneously dispersed Co. The reactivity of the resulting surface oxygen species towards CO were examined by temperature programmed reduction (CO-TPR) and flow reactor kinetic tests. The first morphology exhibited the best performance due to its active Co₃O₄ surface layer, reducing the light-off temperature of CeO₂ by about 200 °C. In contrast, intermixed oxides and Co-doped CeO₂ suffered from lower dispersion and organic residues, respectively. The performance of Co₃O₄-CeO₂ nanocomposites was optimized by varying the Co₃O₄ loading, characterized by X-ray diffraction (XRD) and N₂ sorption (BET). The 16–65 wt % Co₃O₄−CeO₂ catalysts approached the conversion of 1 wt % Pt/CeO₂, rendering them interesting candidates for low-temperature CO oxidation.     

Solvent effect on the kinetics of oxidation of [Co(en)2amS]2+ by IO4−

The dependence of the rate constants for the oxidation of [Co(en)2amS]2+ (amS=–SCH2CH2NH2 2– by IO4– on solvent composition has been established for aqueous mixtures of MeOH, i-PrOH, t-BuOH, urea (U), ethylene carbonate (EC), acetonitrile (AN), dimethyl formamide (DMF) and acetone (Me2CO). Addition of aprotic cosolvents leads to marked decrease in the reaction rate in comparison to monohydroxylic alcohols. Alcohols inhibit the reaction rate in order MeOH < i-PrOH < t-BuOH. The change in solvation on going from the initial to the transition state are discussed in terms of the Gibbs transfer function, Gt0.     

Catalytic CO Oxidation by O2 Mediated with Single Gold Atom Doped Titanium Oxide Cluster Anions AuTi2O4–6−

Gas-phase studies on catalytic CO oxidation by O₂ mediated with gold-containing heteronuclear metal oxide clusters are vital to obtain the structure−reactivity relationship of supported gold catalysts, while it is challenging to trigger the reactivity of clusters with closed-shell electronic structure in O₂ activation. Herein, we identified that CO oxidation by O₂ can be catalyzed by the AuTi₂O_4–6⁻ clusters, among which AuTi₂O₄⁻ with closed-shell electronic structure can effectively activate O₂. The reactions were characterized by mass spectrometry and quantum chemical calculations. Theoretical calculations showed that in the initial stage of O₂ activation, the Ti₂O₄ moiety in AuTi₂O₄⁻ contributes dominantly to activate O₂ into superoxide (O₂⁻⋅) without participation of the Au atom. In subsequent steps, the intimate charge transfer interaction between Au and the Ti₂O₄ moiety drives the direct dissociation of the O₂⁻⋅ unit.     

The unusual electrochemical behaviour of [Co8(CO)18C]2− compared to [M6(CO)15C]2− (M = Co,Rh) and [Fe6(CO)16C]2− carbido clusters

A variety of electrochemical reactions has been observed for the carbido-carbonyl clusters [Co₈(CO)₁₈C](NMe₃CH₂C₆H₅)₂, [Co₆(CO)₁₅C](NMe₃CH₂C₆H₅)₂, [Rh₆(CO)₁₅C](Et₄N)₂ and [Fe₆(CO)₁₆C](Et₄N)₂. The hexanuclear clusters undergo irreversible electrochemical oxidation and reduction steps, whereas the octacobalt species exhibits three electrochemically reversible one-electron steps. The relation between the redox properties and the structure of these clusters is discussed.     

[Fe2S2(CO)6]2− as a cluster precursor: synthesis and structure of [MoFe3S6(CO)6]2− and oxidative decarbonylation to a persulfide-bridged MoFe3S4 double cubane

Reactions of [Fe₂S₂(CO)₆]²⁻ (3) with [Cl₂FeS₂MS₂]²⁻ [M = Mo (4) or W (6)] and [Cl₂FeS₂VS₂FeCl₂]³⁻ (8) in acetonitrile-THF solutions afford the new clusters [MFe₃S₆(CO)₆]²⁻ (M = Mo (5) or W (7)] and [VFe₆S₈(CO)₁₂]³⁻ (9). (Et₄N)₂ (5) crystallizes in orthorhombic space group Pbcn with a = 15.314(7) Å, b = 16.627(6) Å, c = 29.971(13) Å, and Z = 8. Cluster 5 is formed by displacement of chloride from 4 by 3 to yield a species with the [Fe₂(μ₃-S)₂Fe(μ₂-S)₂MoS₂]²⁻ core arrangement containing one Fe(II) and Mo(VI) in distorted tetrahedral sites. Similar structures are proposed for 7 and 9, with the latter containing two 3 ligands bound to the [VFe₂S₄]¹⁺ core of 8. Treatment of 5 with RSSR results in oxidative decarbonylation and formation of [Mo₂Fe₆S₈(S₂)₂(SR)₆]⁴⁻ (10) (R = p-C₆H₄Cl or p-C₆H₄Br), which consists of two [MoFe₃(μ₃-S)₄]³⁺ cubane-type subclusters bridged by two μ₂-η³-S₂²⁻ groups. Cluster 10 was also obtained in a direct-assembly system consisting of [MoS₄]²⁻ + 3FeCl₃+ S₂²⁻ + 7RS⁻ in methanol. Evidence is presented that the solid-state structure of 10 is maintained in solution. The redox change [MoFe₃(μ₂-S)₂(μ₃-S) ₂S₂]²⁻ (5) → [MoFe₃(μ₃-S)₄(S₂)]¹⁺ (10) is described as an oxidatively induced core internal conversion in which there is net Fe and S oxidation and Mo reduction. It is argued that the reduction of tetrahedral Mo(VI) to or near Mo(III), stabilized in a six-coordinate site, is a significant factor in the formation of the cubane structure. The formation of the cubane cluster [VFe₃S₄Cl₃(DMF)₃]¹⁻ from 8 and FeCl₂ is similarly promoted by the reduction of tetrahedral V(V) to or near V(III). The syntheses of 5, 7, 9 and 10 illustrate the utility of 3 as a cluster precursor.     

The Unprecedented [S4N2O10]2− Anion in the Molecular Gold Complexes [Au2Br2(S4N2O10)2] and [Au2Cl2(S4N2O10)2](S2O5Cl2)

The reaction of hexachlorophosphazene, P₃N₃Cl₆, with SO₃ and the gold halides AuCl₃ and AuBr₃, respectively, leads to the new cyclic anionic tetramer, [S₄N₂O₁₀]²⁻, which is coordinated to Au³⁺ in the dimeric complexes [Au₂X₂(S₄N₂O₁₀)₂] (X=Cl, Br). The [S₄N₂O₁₀]²⁻ anion can be seen as the condensation product of two sulfate anions, [SO₄]²⁻_, and two amidosulfate anions, [NH₂SO₃]⁻.     

Co(en)3[B4O5(OH)4]Cl·3H2O和[Ni(en)3][B5O6(OH)4]2·2H2O的合成、结构以及热力学性质

利用水热法合成了两种过渡金属配合物为模板剂的含水硼酸盐晶体Co(en)3[B4O5(OH)4]Cl·3H2O(1) 和 [Ni(en)3][B5O6(OH)4]2·2H2O (2),并通过元素分析、X射线单晶衍射、红外光谱及热重分析对其进行了表征。化合物1晶体结构的主要特点是在所有组成Co(en)33+, [B4O5(OH)4]2–, Cl– 和 H2O之间通过O–H…O、O–H…Cl、N–H…Cl和N–H…O四种氢键连接形成网状超分子结构。化合物2晶体结构的特点是[B5O6(OH)4]–阴离子通过O–H…O氢键连接形成沿a方向有较大通道的三维超分子骨架,模板剂[Ni(en)3]2+阳离子和结晶水分子填充在通道中。     

Stabilization and Binding of [V4O12]4− and Unprecedented [V20O54(NO3)]n− to Lysozyme upon Loss of Ligands and Oxidation of the Potential Drug VIVO(acetylacetonato)2

High-resolution crystal structures of lysozyme in the presence of the potential drug V^IVO(acetylacetonato)₂ under two different experimental conditions have been solved. The crystallographic study reveals the loss of the ligands, the oxidation of V^IV to V^V and the subsequent formation of adducts of the protein with two different polyoxidovanadates: [V₄O₁₂]⁴⁻, which interacts with lysozyme non-covalently, and the unprecedented [V₂₀O₅₄(NO₃)]ⁿ⁻, which is covalenty bound to the side chain of an aspartate residue of symmetry related molecules.     

The substitution kinetics of the aqua ligand by cyanide ions in [Ru(TPPS)(CO)(H2O)]4−

Summary The reaction between the title compound, ,,,-tetra(p-sulphonatophenyl)porphynatoaquacarbonylruthenate(II), [Ru(TPPS)(CO)(H₂O)]^4–, and CN^- revealed that only the aqua ligand is substituted even in the presence of a large excess of the nucleophile. The pK _a1 was spectrophotometrically determined as 13.4(5) (at 33.2 °C) and kinetically as 13.44(5) (at 33.6 °C). The rate of aqua substitution was determined as 89(4)m ^–1 s ^–1 at 35.1 °C and the activation enthalpy and entropy as 55.44(1) kJ mol^–1 and-27.90(4) J K^–1 mol^–1, respectively.     

含有不同配位阳离子的四帽Keggin结构砷钼钒酸盐[Co(en)3][Co(en)2(H2O)2]2@[Mov4MoⅥ4VⅣ8O40(AsO4)]的合成与结构

多金属氧酸盐在催化、医药和材料等方面的应用越来越成为无机化学研究的热点[1～5].水热合成技术在合成多核金属氧酸盐中有独特的优点.在众多的钼钒酸盐中,只有几种双帽及四帽Keggin结构被合成出来[6～13].本文报道一种含有不同配位阳离子的四帽Keggin结构砷钼钒酸盐[Co(en)3]·[Co(en)2(H2O)2]2·[Mov4MoⅥ4VⅣ8O40(AsO4)]的合成与结构.该化合物的结构是由不同的阳离子--1个[Co(en)3]3+和2个[Co(en)2(H2O)2]2+及簇阴离子[Mov4MoⅥ4VⅣ8O40(AsO4)]5-构成的.[Mo8V8O40(AsO4)]5-簇阴离子具有四帽"Keggin"结构,两对V原子位于4个"双帽"位置,簇笼中央是1个{AsO4}四面体.     

Dissociation kinetics of [Fe(phen)3]2+, [Fe(bipy)3]2+ and [Fe-(4,4′-Me2bipy)3]2+ in the presence of cyanide ion in aqueous solution at pressures up to 1 kilobar

Summary Rate constants for dissociation, in aqueous solution at 25° C, of [Fe(phen)₃]²⁺, [Fe(bipy)₃]²⁺, and [Fe(4,4-Me₂bipy)₃]²⁺ in the presence of cyanide, and of the last-named complex also in the presence of hydroxide, are significantly decreased by the application of pressure (up to 1 kbar). Kinetic measurements were carried out using a high pressure cell of improved design to that used in our earlier investigations. Volumes of activation, V ^*, are scarcely sensitive to ligand or to attacking nucleophile, being in the range of 10–12 cm³ mol^–1. An explanation of these results resides in an associative mechanism, a scheme invoked for similar reactions reported previously.     

From an {Fe4S4}-cluster to {Fe2S2}- and {Fe3S}-carbonyls. Crystal structure of [Fe3S(CO)9]2−

We report the electrochemical and chemical synthesis of the first isolable iron carbonyls obtained directly from an {Fe₄S₄}-cluster and carbon monoxide: the structure of one product of chemical reduction, [Fe₃S(CO)₉]²⁻, had been determined by X-ray crystallography.     

Synthesis,characterization and 1H NMR studies of [Co(en)2(malH)2]ClO4·H2O

The trans-[Co(en)₂(malH)₂]ClO₄·H₂O complex was prepared by the reaction of sodium hydrogen malonate with [Co(en)₂(H₂O₂](ClO₄)₃ in the presence of a large concentration of perchlorate ion. It showed a three-band visible spectrum (γγ_max 357, 448 and 542.6 nm), diagnostic of a trans-MA₄B₂ system and gave characteristic IR bands as expected for a trans-bisethylenediamine cobalt(III) complex. The ¹H NMR spectrum in DMSO-d₆ revealed a broad band at 5.8 ppm assignable to the amino hydrogen and a single band at 2.68 for the ethylene group of the chelate ring. The

group of the hydrogen malonate ion appeared as a sharp singlet at 2.95 ppm and integration showed the presence of two bimalonate groups. The reactive methylene protons were found to be exchangeable. Ion association by counter ions of the complex ion in DMSO-d₆ showed no preference among amino protons. This is as expected for trans complexes with D_2h-symmetry.     

Solid-solute phase equilibria in aqueous solution. VI. Solubilities,complex formation,and ion-interaction parameters for the system Na+−Mg2+−ClO 4 − −CO2−H2O at 25°C

The stoichiometric solubility constant of eitelite (NaMg _0.5 CO ₃ +2H⁺ ⇄ Na⁺+0.5Mg ²⁺ +CO ₂ (g)+H ₂ O, log^*K _pso ^I =14.67±0.03 was determined at I=3 m (mol kg⁻¹) (NaClO ₄ ) and 25°C. The stability of magnesium (hydrogen-)carbonato complexes in this ionic medium was explicitely taken into account. Consequently, trace activity coefficients of free ionic species, calculated from the Pitzer model with ion-interaction parameters from the literature, were sufficient for an evaluation of the thermodynamic solubility constants and Gibbs energies of formation for eitelite (−1039.88±0.60), magnesite (−1033.60±0.40), hydromagnesite (−1174.30±0.50), nesquehonite (−1724.67±0.40), and brucite (−835.90±0.80 kJ-mol ⁻¹ ). The increasing solubilities of nesquehonite and eitelite at higher sodium carbonate molalities were explained by invoking a magnesium dicarbonato complex (Mg²⁺+2CO ₃ ²⁻ ⇄ Mg(CO₃) ₂ ²⁻ , log β_z = 3.90 ± 0.08). A set of ion-interaction parameters was obtained from solubility and dissociation constants for carbonic acid in 1 to 3.5 m NaClO ₄ media which reproduce these constants to 0.02 units in log K. The following Pitzer parameters are consistent with the previously studied formation of magnesium (hydrogen-)carbonato complexes in 3m NaClO ₄ . The model and Gibbs functions of solid phases derived here reproduce original solubility data (−log [H⁺], [Mg ²⁺ ] _tot ) measured in perchlorate medium within experimental uncertainty. Presented at the XXII International Conference on Solution Chemistry, July 14–19, 1991, Linz, Austria.     

新型磷-钒-氧层状化合物[H2en]2[H3O]6[Co(H2O)2(VO)8(OH)4(PO4)8]的水热合成与晶体结构

金属磷酸盐材料在吸附、离子交换、离子传导和催化剂方面有潜在的应用前景[1～5]. 近年来, 通过水热反应合成了一些A-V-P-O化合物. 在这些化合物中, A一般为碱金属或有机阳离子, 如层状结构的[H2N(C4H8)2NH2][(VO)4(OH)4(PO4)2][6] 和[H2N(C2H4)3NH2][(VO)8(HPO4)3(PO4)4*(OH)2]*2H2O[6], 一维链状结构的 [H2NCH2CH2NH3(VO)(PO4)][7], 手性双螺旋结构的 [(CH3)2NH2]K4[(VO)10(H2O)2(OH)4(PO4)7]*H2O[8]以及具有三维骨架结构的化合物 [H3N(CH2)3NH3K(VO)3(PO4)3][9], [H3N(CH2)3NH3]2[V(H2O)2(VO)6(OH)2(HPO4)3(PO4)5]*3H2O[10]和[H3N(CH2)2NH3][(VO)3(H2O)2(PO4)2(HPO4)4][11].     

Co-ordination of copper and silver by [Co2{μ-C2(CH2SCH2CH2)2S}(CO)6]

The thiamacrocycle [Co₂{μ-C₂(CH₂SCH₂CH₂)₂S}(CO)₆] reacts with Ag[BF₄] and PPh₃ to afford the fluxional compound [Co₂{μ-C₂(CH₂SCH₂)₂S}(CO)₆(AgPPh₃)][BF₄], the structure of which has been established by X-ray crystallography, and with [Cu(CH₃₋CN)₄][PF₆] to afford [Co₂{μ-C₂(CH₂SCH₂CH₂)₂S}(CO)₆(CuCH₃₋CN)][PF₆], which undergoes phosphine sustitution.     

Vapor–liquid equilibrium data for the carbon dioxide (CO2) + difluoromethane (R32) system at temperatures from 283.12 to 343.25 K and pressures up to 7.46 MPa

Isothermal vapor–liquid equilibrium (VLE) data have been measured for the binary system carbon dioxide (CO₂)+difluoromethane(R32) at eight temperatures between 283.12 and 343.25 K, and at pressures in the range 1.11–7.46 MPa. The experimental method used in this work is of the static-analytic type, taking advantage of two pneumatic capillary samplers (Rolsi™, Armines’ Patent) developed in the Cenerg/TEP laboratory. The data were obtained with uncertainties within ±0.02 K, ±0.002 MPa, and ±1% for molar compositions. The isothermal P, x, and y data are well represented with the Peng–Robinson equation of state (PR EoS) using the Mathias Copeman alpha function and the Wong–Sandler mixing rules involving the NRTL model.     

Synthesis and Structure of [Co2Bi2(α or β-Β-CoW9O34)2]14− Isomers and Their Catalytic Water Oxidation

A new sandwich-type complex based [α-Β-CoW₉O₃₄]^12? as ligand, Na₉H₅[Co₂Bi₂(α-Β-CoW₉O₃₄)₂]·54H₂O 2, has been synthesized and characterized structurally by elemental analysis, single-crystal X-ray diffraction, IR, XRD and TG. Structural analysis indicates that the anion of 2 is isomeric with that of Na₁₄[Co₂Bi₂(β-Β-CoW₉O₃₄)₂]·48H₂O 1. It is constructed through sandwiching Bi^III and Co^II ions with [α-B-Co^IIW₉O₃₄]^12? anions. Cyclic voltammetry experiments are carried out in 50 mM sodium phosphate buffer (pH = 7.4) containing 1 mM [Ru(bpy)₃]²⁺ solution. It is found that both 1 and 2 exhibit catalytic activity of the electrochemical oxidation of H₂O into O₂. Visible-light-induced catalytic activity of 1 and 2 are investigated by using [Ru(bpy)₃]²⁺ as a photosensitiser and S₂O₈ ^2? as a sacrificial electron acceptor. In 40 min, 16.8 and 5.3 μmol of O₂ are produced for 1 and 2 respectively.