Synthesis and crystal chemistry of NH3(MoO3)3

NH₃(MoO₃)₃ crystallizes with hexagonal symmetry, space group $\text{P6}{}_3\text{m}$, lattice constants a = 10.568 Å, c = 3.726 Å, and Z = 2. The crystal structure has been determined by Patterson synthesis and refined assuming isotropic temperature factors to a final conventional R value of 0.085. The structure shows a three-dimensional arrangement built up of double chains of distorted MoO₆ octahedra, parallel to the [001] direction. The octahedral double chains are linked among each other through common oxygen atoms. In addition to the shared oxygen atoms, each molybdenum is coordinated to one terminal oxygen. MoO distances range from 1.645 to 2.378 Å and OMoO angles from 74.3 to 114.3°. These results are consistent with the fact that molybdenum in high-valence states shows octahedral coordination with terminal oxygens.     

The molybdenum-molybdenum triple bond—XVII. Syntheses,spectroscopic and structural characterizations of Mo4F4(O—t-Bu)8 and Mo2F2(O—t-Bu)4(PMe3)2 (MoMo)

Hydrocarbon solutions of Mo₂(O—t-Bu)₆ and PF₃ (2 equiv) yield Mo₄F₄(O—t-Bu)₈, I, and PF₂(O—t-Bu). Compound I contains a bisphenoid of molybdenum atoms with two short MoMo distances, 2.26 Å, and four long MoMo distances, 3.75 Å, corresponding to localized MoMo triple bonding and non-bonding distances, respectively. The tetranuclear compound may be viewed as a dimer, [Mo₂(μ₂-F)₂(O-t-Bu)₄]₂, and addition of PMe₃ to hydrocarbon solutions of I yields Mo₂F₂(O—t-Bu)₄(PMe₃)₂, II, which contains an unbridged MoMo triple bond of distance 2.27 Å. Each molybdenum atom is coordinated to two oxygen atoms, one fluorine atom and the phosphorus atom of the PMe₃ ligand in a roughly square planar manner. The overall central Mo₂O₄F₂P₂ skeleton has C₂ symmetry and NMR studies (¹H, ¹⁹F and ³¹P) are consistent with the maintenance of this type of structure in solution. Infrared and electronic absorption spectral data are reported. These are the first compounds containing fluorine ligands attached to the (MoMo)⁶⁺ unit.     

一个新的夹心型杂多钨酸盐Na6(C5N2H7){[Na(H2O)2]3Co(H2O)5-[Co(H2O)]3(AsW9O33)2}•27H2O的晶体结构及性质

在pH＝7.5的水溶液中, Na₂WO₄•2H₂O, NaAsO₂, CoCl₂•6H₂O与对氨基吡啶反应, 得到了一种新的夹心型杂多钨酸盐Na₆(C₅H₇N₂){[Na(H₂O)₂]₃Co(H₂O)₅[Co(H₂O)]₃(AsW₉O₃₃)₂}•27H₂O单晶, 用X射线单晶衍射法及元素分析确定了其结构, 晶体属三斜晶系, P 空间群, 其晶胞参数为: a＝1.3276(8) nm, b＝1.7581(10) nm, c＝2.4381(14) nm, α＝70.954(9)°, β＝86.663(9)°, γ＝72.885(9)°, V＝5.136(5) nm³, Z＝2, R₁＝0.0608, wR₂＝0.0848 [I＞2σ(I)]. 在{[Na(H₂O)₂]₃Co(H₂O)₅[Co(H₂O)]₃(AsW₉O₃₃)₂}^7－阴离子中, 一个Co^2＋与聚阴离子{[Na(H₂O)₂]₃[Co(H₂O)]₃(AsW₉O₃₃)₂}^9－的一个端基氧共价连接, Co^2＋呈现出5和6两种配位数, 质子化的氨基吡啶正离子作为抗衡离子存在于晶体之中. 对标题化合物进行了IR, UV-Vis, TG-DSC表征. 对该化合物、Na₂WO₄•2H₂O及CoCl₂•6H₂O催化H₂O₂氧化乙醛的活性进行了比较研究, 该化合物的催化活性远优于简单化合物Na₂WO₄•2H₂O和CoCl₂•6H₂O.     

Oxygen evolution on SrFeO3 electrode

Oxygen evolution reactions on SrFeO₃ were investigated in alkaline and acidic solutions. It was found that the catalytic activity for the oxygen evolution reaction in the alkaline solution is high. The following reaction steps (V)+Fe+2H₂O→(O)+FeOH₂+2H⁺+2e^? in acidic solution and FeOH+OH^?→FeO^?+H₂O in alkaline solution are presumed to be rate-controlling in the anodic evolution of oxygen on SrFeO₃ electrode, where (V) denotes oxygen vacancy on the electrode surface. The reaction mechanism and the catalytic property are discussed in connection to the band structure of the oxide.     

Low-temperature heat capacity of triangle antiferromagnetic molecular clusters K12[(VO)3(SbW9O33)2]·15H2O and K12[(VO)3(BiW9O33)2]·29H2O

Energy level diagrams have been determined for two molecular clusters, K₁₂[(VO)₃(SbW₉O₃₃)₂]·15H₂O and K₁₂[(VO)₃(BiW₉O₃₃)₂]·29H₂O, by low-temperature heat capacity measurements down to 85 mK under magnetic field strengths up to 9 T. Both compounds exhibit a broad heat capacity peak dependent upon the magnetic field, which can be explained by the thermal excitation in the magnetic energy levels. A detailed analysis based on the numerical calculation reveals that the spin-spin interaction between the V⁴⁺ ions includes a Dzyaloshinskii-Moriya interaction.     

Coordination of water to organolead(IV) nitrates: The examples of [PbPh2(NO3)2(H2O)2] and [PbMe3(NO3)(H2O)]

The compound [PbPh₂(NO₃)₂(H₂O)₂] was synthesized and characterized by spectroscopic methods (IR; ¹H, ¹³C and ²⁰⁷Pb NMR) and mass spectrometry. An X-ray diffraction study showed that the crystal is a supramolecular tridimensional network of hydrogen-bonded PbPh₂(NO₃)₂(H₂O)₂ units in which the Pb atom is octacoordinated and adopts a distorted hexagonal bipyramidal geometry, with four O (bidentate nitrate) and two O (water) atoms in equatorial positions and two C-phenyl atoms in axial positions. The crystal of [PbMe₃(NO₃)(H₂O)], obtained as a byproduct in the synthesis of PbMe₂(NO₃)₂, contains chains of hydrogen-bonded PbMe₃(NO₃)(H₂O) units in which the Pb atom is pentacoordinated with a slightly distorted trigonal bipyramidal environment. In this arrangement the three C-methyl atoms are equatorial and the O atoms from the monodentate nitrate and the water molecule are axial.     

A Suberato-Pillared Mn(II) Coordination Polymer: Hydrothermal Synthesis, Crystal Structure, and Magnetic Properties of Mn2(H2O)[O2C(CH2)6CO2]2

A suberato-pillared Mn(II) coordination polymer Mn₂(H₂O)(C₈H₁₂O₄)₂ was hydrothermally synthesized at 170°C for 3 days and characterized by single-crystal X-ray diffraction. Crystal data: monoclinic, C2/c, Z=4, a=26.544(5), b=7.617(2), c=9.187(2) Å, β=105.38(2)°, V=1791.0(7) ų, R₁=0.064 and wR₂=0.162. The compound shows a layered structure consisting of inorganic Mn oxygen polyhedral layers and organic regions. The inorganic Mn oxygen layers are generated from Mn₂O₁₀ bioctahedral units, which share corners with neighbors to form zigzag chains along the [001] direction and are, along the [010] direction, further connected by carboxylate groups of the suberato ligands and hydrogen bonds. The magnetic studies indicated that the compound becomes antiferromagnetic at low temperatures with T_Néel=12 K and follows Curie-Weiss law χ_m(T+22.429)= 4.48 cm³ mol⁻¹ K between 25 and 300 K. Upon heating in Ar stream, Mn₂(H₂O)(C₈H₁₂O₄)₂ decomposes in three steps.     

[Ag(NH3)2]Ag(OsO3N)2: a new nitridoosmate(VIII)

Dark brown single crystals of [Ag(NH₃)₂]Ag(OsO₃N)₂ were obtained from the reaction of Ag₂CO₃, OsO₄, and NH₃ in aqueous solution. The crystal structure was solved in the monoclinic space group C2/m, with the following unit-cell dimensions: a=1962.5(3), b=633.1(1), c=812.6(1) pm, β=96.71(1)°. The final reliability factor was R=0.0256 for 1034 reflections with I>2σ(I). Linear [Ag(NH₃)₂]⁺ ions are present oriented perpendicular to the [010] direction, leading to short Ag⁺-Ag⁺ distances of 316 pm. A second type of Ag⁺ ions in the crystal structure present coordination number “6+1” and are surrounded by oxygen and nitrogen atoms of the nitridoosmate groups. Within the first of the two crystallographically distinguishable anions one can clearly differentiate between oxygen and nitrogen atoms while the second one exhibits a N/O disorder over two positions. The infrared spectrum of [Ag(NH₃)₂]Ag(OsO₃N)₂ shows the typical absorptions which can be attributed to the complex anions and the NH₃ ligands.     

Solid-state decomposition studies on fluoroperoxo species of transition metals. Part VI. Kinetics of isothermal decomposition of M2Zr2(O2)2F6 · 2 H2O (M = Rb+, or Cs+)

The decomposition of solid fluoroperoxozirconates of alkali metals, M₂Zr₂(O₂)₂F₆ · 2 H₂O (M = Rb⁺, Cs⁺), is carried out in vacuum under isothermal conditions. The stoichiometry of the reaction may be represented by the equation, M₂Zr₂(O₂)₂F₆ · 2 H₂O(S) — M₂Zr₂O₂F₆(s) + O₂(g) + 2 H₂ O(g) (condensed). The fractional decomposition α is determined by measuring the pressure of oxygen evolved during pyrolysis with a McLeod gauge. The α values range from 0.06 to 0.70 for the rubidium and from 0.06 to 0.79 for the caesium species in the temperature ranges 107–202°C and 101–219°C, respectively. The α—time data for both compounds show that the kinetics are deceleratory throughout the course of the decomposition reaction. In both compounds, the initial stages of decomposition are described by a unimolecular decay law, while the later stages obey a contracting volume equation at all temperatures. The activation energies from Arrhenius plots are 14.0 and 10.9 kcal mole^?1 for the rubidium and 12.9 and 11.2 kcal mole^?1 for the caesium compound.     

Darstellung und chemie von Me2TlN(SiMe3)2 und Tl[N(SiMe3)2]3

The complexes [Rh(η³-C₃H₄R)(η⁵-C₅R′₅)L]⁺BF₄^- (R  1-Me, R′  H, Me; R  2-Me, R′  H) (L  C₅H₅N, Ph₃P, Ph₃As) have been prepared from Rh(η³-C₃H₄R)(η⁵-C₅R′₅)Cl and AGBF₄ in acetone, followed by reaction with the stoicheiometric quantity of L. The ¹H and ¹³C NMR spectra of the salts are reported and discussed.     

Crystal Structure of (H3O)4[(C2H5)4N]6 [Th2Cl4(H2O)12O]3[Re4Se4(CN)12]4

Crystals of the rhenium cluster complex (H₃O)₄[(C₂H₅)₄N]₆[Th₂Cl₄(H₂O)₁₂O]₃[Re₄Se₄(CN)₁₂]₄ are obtained in an acidic (HCl) aqueous solution by the reaction of cluster salt K₄[Re₄Se₄(CN)₁₂]·6H₂O with ThCl₄ and (C₂H₅)₄NCl. Single crystal X-ray analysis shows that the title compound is ionic and crystallizes in the cubic crystal system (a = 22.7322(3) ?, V = 11746.93(27) ?³, Z = 2, I4 3m space group, R = 0.0350). It contains [Th₂Cl₄(H₂O)₁₂O]²⁺ cations with two thorium atoms bonded to each other through the bridging oxygen atom forming an angle of 180° in the structure.     

Closest packing in dense oxides: The structure of a polymorph of Co3(AsO4)2

Crystals of Co₃(AsO₄)₂ were grown from the melt of a mixture of Co₂As₂O₇ and As₂O₅. The crystals are isostructural with Mg₃(AsO₄)₂ and are tetragonal with a = 6.858(2), c = 18.872(5) Å, Z = 6, and space group $\text{I}\text{4}\text{2d}$. A total of 1048 independent reflections were measured by diffractometer and used in the full-matrix refinement to a final R value of 0.069. The structure contains two distinct AsO₄ groups. Two of the cobalt ions are octahedrally coordinated and a third occupies a $\text{4}$ site with four short and four long CoO distances. The crystal structure of Co₃ (AsO₄)₂ is not based on the continuous three-dimensional closest packing of oxygen atoms. Nevertheless the number of oxygen atoms per cubic centimeter is 5.4 × 10²², which falls in the range of values for hexagonal and cubic closest packed structures. A better measure of the degree to which closest packing is achieved by a structure is suggested. It is based on an analysis of the polyhedra of oxygen atoms which surround each of the oxygen atoms in a structure and their relation to the polyhedra in ideally closest packed structures. In order to facilitate the analysis, polytopes of 11- and 12-vertex polyhedra were studied. A new decahexahedral 11-vertex polyhedron was found.     

稀土配合物[Pr(C3H7NO2)2(C3H4N2)(H2O)](ClO4)3的标准生成焓及热分解动力学研究

合成了高氯酸镨和咪唑(C₃H₄N₂), DL-α-丙氨酸(C₃H₇NO₂)混配配合物晶体. 经傅立叶变换红外光谱、化学分析和元素分析确定其组成为[Pr(C₃H₇NO₂)₂(C₃H₄N₂)(H₂O)](ClO₄)₃. 使用具有恒温环境的溶解-反应量热计, 以2.0 mol•L^－1 HCl为量热溶剂, 在T＝(298.150±0.001) K时测定出化学反应PrCl₃•6H₂O(s)＋2C₃H₇NO₂(s)＋C₃H₄N₂(s)＋3NaClO₄(s)＝[Pr(C₃H₇NO₂)₂(C₃H₄N₂)(H₂O)](ClO₄)₃(s)＋3NaCl(s)＋5H₂O(1)的标准摩尔反应焓为Δ_rH_m^ө＝(39.26±0.11) kJ•mol^－1. 根据盖斯定律, 计算出配合物的标准摩尔生成焓为Δ_fH_m^ө{[Pr(C₃H₇NO₂)₂(C₃H₄N₂)(H₂O)](ClO₄)₃(s), 298.150 K}＝(－2424.2±3.3) kJ•mol^－1. 采用TG-DTG技术研究了配合物在流动高纯氮气(99.99%)气氛中的非等温热分解动力学, 运用微分法(Achar-Brindley-sharp和Kissinger法)和积分法(Satava-Sestak和Coats-Redfern法)对非等温动力学数据进行分析, 求得分解反应的表观活化能E＝108.9 kJ•mol^－1, 动力学方程式为dα/dt＝2(5.90×10⁸/3)(1－α)[－ln(1－α)]^－1exp(－108.9×10³/RT).     

Crystal structure and luminescence property of novel three-dimensional network of {Eu2(p-BDC)3(Phen)2(H2O)2}n

The single crystal of a supramolecule, {Eu₂(p-BDC)₃(Phen)₂(H₂O)₂}_n (p-BDC=1,4-benzenedicarboxylate), with characteristic luminescence of Eu³⁺ was obtained by means of soft chemistry. The crystal structure determination reveals that each Eu³⁺ ion is coordinated by five oxygen atoms of p-BDC anions, one oxygen atom from water molecule, and two nitrogen atoms of Phen, respectively, resulting in an eight-coordinated Eu³⁺ center and a distorted square antiprism coordination polyhedron. Four bridges, two carboxylates of μ₄-p-BDC and two of μ₃-p-BDC, connect two Eu atoms into a binuclear unit. Moreover, the μ₃-p-BDC integrates the binuclear building blocks at the direction of b axis and the μ₄-p-BDC polymerizes the structure roughly along the direction of the sum vector of axis b and c, respectively, forming two-dimensional layers. Hydrogen bonds between layers make the structure a three-dimensional network. The luminescence spectra measured under 77 K demonstrate the antenna effect of Phen and the ⁵D₁→⁵D₀ energy transfer path within Eu³⁺ ion. Both luminescence spectra and crystal structure lead to the conclusion that the local symmetry around the Eu³⁺ ion is C₁ and that more than one Eu³⁺ ion sites having slight environmental difference are present.     

Reaction of O(1D2) with propylene

The reaction of excited oxygen atom, O(¹D₂), with propylene has been studied under helium pressure up to 150 atm. The identified oxides and their limiting fractional yields are as follows: propylene oxide 0.22, propionaldehyde 0.22, acetone 0.11, allylalcohol 0.20, acrolein 0.02 and acetaldehyde 0.06. The mechanism of primary attack of O(¹D₂) on olefin is inferred on the basis of these figures.     

Potassium trifluoroperoxotitanate(IV) trihydrate,K[Ti(O2)F3] · 3H2O

Potassium trifluoroperoxotitanate(IV) trihydrate, K[Ti(O₂)F₃] · 3H₂O, with the peroxide (O₂^2?) being bonded to the Ti(IV) centre in a triangular bidentate manner (C_2ν) as evidenced from the IR and laser Raman spectroscopic studies, has been synthesised from the reaction of a solution of TiO₂in 40% HF with an excess of 30% H₂O₂ and KOH, followed by the addition of aqueous HF to adjust the pH of the reaction solution between 8 and 9.     

The molecular structure of the complex trimethylaluminium dimethyl ether, (CH3)3AlO(CH3)2, determined by gas phase electron diffraction

The molecular structure of (CH₃)₃AlO(CH₃)₂ has been determined by gas phase electron diffraction. The main molecular parameters are AlC = 1.973(11), AlO = 2.014(14), OC = 1.436(3) Å, OAlC = 98.7(1.5), AlOC = 122.6 (0.5) and COC = 114.5(1.7)°. The OC bond distance and the COC valence angle are significantly larger than those in free dimethyl ether. The three valencies of the oxygen atom appear to lie in one plane. It is suggested that the planarity of the oxygen atom is due to across-angle repulsion Al?C(O).     

Synthesis and Structure of a New Organic-Inorganic Framework with Tetranuclear Clusters, [Co4(OH)2(H2O)2](C4H11N2)2[C6H2(COO)4]2·3H2O

A new hybrid organic-inorganic three-dimensional compound, [Co₄(OH)₂(H₂O)₂](C₄H₁₁N₂)₂[C₆H₂(CO₂)₄]₂·3H₂O 1, has been synthesized via hydrothermal reactions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and magnetic techniques. Compound 1 crystallizes in the monoclinic space group P2₁/n (no. 14) with a=6.3029(9) Å, b=16.413(2) Å, c=17.139(2) Å, β=98.630(2)°, V=1735.0(4) ų, Z=2. Compound 1 contains tetranuclear Co₄(μ₃-OH)₂(H₂O)₂ clusters that are inter-linked by pyromellitate bridging ligands into a three-dimensional structure containing one-dimensional tunnels along the a-axis with water and pendant monoprotonated piperazine molecules in the center. The variable temperature magnetic susceptibility was measured from 2 to 300 K at 5000 Oe showing a predominantly anti-ferromagnetic interaction in 1, and the field dependence of magnetization was measured at 2, 5, 15, and 20 K indicating the competition of magnetic interactions in the tetranuclear centers.     

Ethylene addition to OsO3(CH2) - A theoretical study

Quantum chemical calculations at the B3LYP/TZVP level of theory have been carried out for the initial steps of the addition reaction of ethylene to OsO₃(CH₂). The calculations predict that there are two reaction channels with low activation barriers. The kinetically and thermodynamically most favored reaction is the [3+2]_O, C addition which has a barrier of only 2.3 kcal mol⁻¹. The [3+2]_O, O addition has a slightly higher barrier of 6.5 kcal mol⁻¹. Four other reactions of OsO₃(CH₂) with C₂H₄ have significantly larger activation barriers. The addition of ethylene to one oxo group with concomitant migration of one hydrogen atom from ethylene to the methylene ligand yields thermodynamically stable products but the activation energies for the reactions are 16.7 and 20.9 kcal mol⁻¹. Even higher barriers are calculated for the [2+2] addition to the OsO bond (32.6 kcal mol⁻¹) and for the addition to the oxygen atom yielding an oxiran complex (41.2 kcal mol⁻¹). The activation barriers for the rearrangement to the bisoxoosmaoxirane isomer (36.3 kcal mol⁻¹) and for the addition reactions of the latter with C₂H₄ are also quite high. The most favorable reactions of the cyclic isomer are the slightly exothermic [2+2] addition across the OsO bond which has an activation barrier of 46.6 kcal mol⁻¹ and the [3+2]_O, O addition which is an endothermic process with an activation barrier of 44.3 kcal mol⁻¹.     

Three-dimensional five-connected coordination polymer [M2(C3H2O4)2(H2O)2(μ2-hmt)]n with 46 topologies (M=Zn, Cu; hmt=hexamethylenetetramine)

Two novel three-dimensional five-connected coordination polymers [M₂(C₃H₂O₄)₂(H₂O)₂(μ₂-hmt)]_n with 4⁴6⁶ topologies (M=Zn, Cu; hmt=hexamethylenetetramine) were synthesized and characterized by elemental analysis, crystal structure, IR, thermal gravimetric analyses. Both [Zn₂(C₃H₂O₄)₂(H₂O)₂(μ₂-hmt)]_n and [Cu₂(C₃H₂O₄)₂(H₂O)₂(μ₂-hmt)]_n all crystallize in the orthorhombic system, space group Imm2, and with Z=2. Metal ions have all octahedral geometry coordinated by four oxygen atoms from three malonates, one oxygen atom from a water molecule and one nitrogen atom of hmt ligand. Each malonate binds a metal ion with its two oxygen atoms in a chelating mode and connects to adjacent two metal ions with another two oxygen atoms to form an infinite wavy layer. The layers are bridged by μ₂-hmt molecules to form a three-dimensional framework with channels. The magnetic susceptibility data show there is a weak antiferromagnetic exchange interaction in the complex [Cu₂(C₃H₂O₄)₂(H₂O)₂(μ₂-hmt)]_n.