A new method of synthesis of the B<Subscript>3</Subscript>H<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack> anion

A new method of synthesis of the B₃H₈⁻ anion has been suggested. The method uses the reaction of some metal halides (CuCl, SnCl₂, CrCl₃, PbF₂, PbCl₂, PbBr₂, and BiCl₃) with sodium tetrahydroborate. It is characterized by high (up to quantitative) yields and simplicity of isolation of the target products ((n-C₄H₉)₄N)[B₃H₈] and Cs[B₃H₈].     

The ESCA analysis of the B<Subscript>3</Subscript>H<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack> anion

Compounds [Et₄N]₂B₃H₈ and CsB₃H₈ are studied using the ESCA method. The results of analysis of the B1s electron spectra and estimation of the effective charge differences in [Et₄N]₂B₃H₈ are compared to the data of theoretical calculations of the B₃H₈⁻ anion.     

Influence of ion size on the stability of chloroplumbates containing PbCl<Stack><Subscript>5</Subscript><Superscript>−</Superscript></Stack> or PbCl<Stack><Subscript>6</Subscript><Superscript>2−</Superscript></Stack>

The enthalpies of formation of PbCl₄, PbCl₅⁻ and PbCl₆²⁻, originating from quantum mechanics, have enabled the thermodynamic behaviour of these ions with respect to Cl-detachment to be assessed. The stability of salts containing PbCl₅⁻ and PbCl₆²⁻ as a function of the dimensions of these anions and complementary cations was studied using an approach combining the Kapustinskii-Yatsimirskii equation with basic thermochemical relationships. It was found that hexachloroplumbates of monovalent metal cations will not dissociate into metal chlorides and PbCl₄, provided the complementary cations are suitably large in size. Hexachloroplumbates of divalent metal cations have not yet been synthesised since no known metal cations attain the requisite large size. Such salts will not dissociate if the divalent metal cations are able to complex suitably large electron-donating ligands. The pentachloroplumbates of both monovalent and divalent metal cations are unstable, since no known metal cations have appropriately large ionic radii. The approach adopted appears to be useful for the examination of the thermal behaviour, stability and reactivity of chloroplumbates.     

Chemical Bonding in the Complexes XeF<Stack><Subscript>5</Subscript><Superscript>+</Superscript></Stack>XF<Stack><Subscript>6</Subscript><Superscript>−</Superscript></Stack> (X = P,As, Sb,and Bi)

Ab initio quantum-chemical calculations of the complexes XeF ₅ ⁺ XF ₆ ^? (X = P, As, Sb, and Bi) were performed with the use of relativistic pseudopotentials for heavy atoms and full-electron basis sets. The chemical bonds were characterized by the parameters of critical points (electron density, its Laplacian, total electron energy, and its kinetic and potential components). It was demonstrated that the interaction between the XeF ₅ ⁺ cation and the XF ₆ ^? anion in XeF ₅ ⁺ XF ₆ ^? follows a key-lock scheme involving directed interactions of bridging fluorine atoms F_b → Xe and that the structuring function of the lone electron pair of the Xe atom is to compensate the destabilizing electrostatic interaction between the Xe and X atoms bearing excess positive charges.     

Synthesis and Structure of the bismuth complex [Ph<Subscript>3</Subscript>PrP]<Stack><Subscript>4</Subscript><Superscript>+</Superscript></Stack>[Bi<Subscript>4</Subscript>I<Subscript>16</Subscript>]<Superscript>4−</Superscript>

The complex [Ph₃P] ₄ ⁺ [Bi₄I₁₆]^4? · 2 Me₂C=O (I) was synthesized by the reaction of triphenyl(propyl)phosphonium iodide with bismuth iodide in acetone. The crystal structure of complex I was determined by X-ray crystallography. It contains, in addition to solvent molecules, two types of crystallographically independent tetrahedral tetraphenyl(propyl)phosphonium cations and tetranuclear anions [Bi₄I₁₆]^4? in a chair conformation with the bismuth atoms being in an octahedral coordination. The Bi-I distances in the anion vary within 2.8768(4)–3.2524(4) Å.     

Study on nonlinear kinetic and thermodynamics of oscillating reaction of amino Acid-BrO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>-Mn<Superscript>2+</Superscript>-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-acetone system

With the help of the kinetic parameters (the rate constant (k _in k _p) and the apparent activation energy (E _in E _p) of the oscillatory induction period and oscillation period) of the oscillating reaction using thirteen amino acids, leucine (Leu), threonine (Thr), arginine (Arg), lysine (Lys), histidine (His), alanine (Ala), glutamine (Glu), glycine (Gly), methionine (Met), cystine (Cys), tryptophan (Trp), serine (Ser) and tyrosine (Tyr), as organic substrates in amino acid-BrO₃⁻-Mn²⁺-H₂SO₄-acetone system, then based on the Oregonator model and the thermodynamics theory on irreversible process, the thermodynamic function (ΔH _in, ΔG _in, ΔS _in and ΔH _p, ΔG _p, ΔS _p) of these oscillating system are studied. The results indicate the entropy ΔS of these oscillating reaction are negative, thereby it is proved that the oscillating reaction is a noequilibrium system with dissipation structure in agreement with the character of the oscillating reaction from disorder to order in irreversible thermodynamics. These are satisfactorily to explain the experimental phenomena.     

Comparison of Magnetic Properties between Spin Singlet and Triplet Li<Subscript>3</Subscript>Al<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> Clusters

With a second-order Møller–Plesset perturbation theory and Hartree–Fock nuclear magnetic resonance calculations, we investigated the magnetic properties of spin singlet and triplet Li₃Al ₄ ^? clusters. The obtained gauge-independent atomic orbital magnetic shielding tensors confirm the paramagnetism of singlet Li₃Al ₄ ^? and diamagnetism of the triplet. The planar rings composed of four aluminum atoms make the magnetic properties of Li₃Al ₄ ^? clusters versatile. The localized molecular orbital, low symmetry of geometric conformation and narrow gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are found to correlate with the paramagnetism of singlet Li₃Al ₄ ^? . The origin of the paramagnetism is explained. In triplet Li₃Al ₄ ^? , the two outmost orbitals are degenerate, causing a conversion from the paramagnetism to diamagnetism.     

Mercury complex [(HOCH<Subscript>2</Subscript>)<Subscript>3</Subscript>CNH<Subscript>3</Subscript>]<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> [HgI<Subscript>4</Subscript>]<Superscript>2−</Superscript>: Synthesis and structure

The complex [(HOCH₂)₃CNH₃] ₂ ⁺ [HgI₄]^2? (I) was synthesized by reacting (trioxymethyl)methylammonium iodide with mercury dioide (2: 1 mol/mol) in acetone. X-ray crystallography shows that the complex consists of two types of crystallographically independent [(HOCH₂)₃CNH₃]⁺ cations and tetrahedral anions [HgI₄]^2? (IHgI, 106.49(2)°–113.99(4)°; Hg-I, 2.7849(8)-2.8105(8) Å. [(HOCH₂)₃CNH₃]⁺ cations are linked via hydrogen bonds O…H-N and O-H…N (O…N, 2.84–2.92 Å) to form polymer chains, which are cross-linked with one another via anions (I…H, 2.81, 2.82 Å).     

Isochoric isothermal pyrolysis of trifluoroiodomethane: CF<Stack><Subscript>3</Subscript><Superscript>·</Superscript></Stack> recombination kinetics

The rate constant of CF ₃ ^· recombination (\(k_{(CF_3 )_2 }^M \)) in the isochoric isothermal pyrolysis of trifluoroiodomethane at T = 625–732 K and P = 29–300 Torr was derived from molecular iodine accumulation curves. Using literature data for the high-pressure limit and the results of our measurements, an analytical expression for \(k_{(CF_3 )_2 }^M \) was set up for T = 300–1300 K and any pressure of the buffer gas CF₃I.     

Quantum Chemical Study of Niobium and Tantalum M<Subscript>4</Subscript>O<Subscript>10</Subscript> Oxide Clusters and M<Subscript>4</Subscript>O<Stack><Subscript>10</Subscript><Superscript>–</Superscript></Stack> Anions

Structural parameters and vibrational frequencies of the clusters (T_d)–Nb₄O₁₀, (C_3v)-TaNb₃O₁₀, (D_2d)-Nb₄O ₁₀ ^– , and (C_s)-TaNb₃O ₁₀ ^– were calculated. According to the (U)DFT/SDD calculations with BLYP, B3LYP, and PBE0 functionals magnetization of the anion (D_2d)-Nb₄O ₁₀ ^– is distributed equally among four niobium atoms. In the anion (C_s)-TaNb₃O ₁₀ ^– unpaired electron presumably occupies niobium atoms. The distinction in contributions from Nb atoms in the magnetization of the tantalum-containing cluster grows with the exchange component of the DFT functional in the series of functionals BLYP < B3LYP < PBE0 < UHF.     

Formation of a Cluster H<Subscript>2</Subscript>V<Subscript>10</Subscript>O<Stack><Subscript>28</Subscript><Superscript>4–</Superscript></Stack> under the Action of Brønsted Acids and Its Catalytic Activity in Oxidation of Alkylbenzenes

New method was developed for the preparation of vanadium cluster of the composition {Me₂NH₂}₄* H₂V₁₀O₂₈ from vanadyl(IV) acetylacetonate in the presence of 2-hydroxy-2-trifluoromethylchroman-4-one or its synthetic precursor, 2′-hydroxyacetophenone. The structure of the cluster was proved by X-ray diffraction (XRD) analysis. The cluster of decavanadate catalyzes oxidation of toluene and o-xylene creating promising situation for developing new catalytic materials.     

Reaction of the [B<Subscript>10</Subscript>H<Subscript>9</Subscript>O<Subscript>2</Subscript>C<Subscript>4</Subscript>H<Subscript>8</Subscript>]<Superscript>–</Superscript> anion with C-nucleophiles

The reactions of 1,4-dioxane-substituted closo-decaborate anion ([B₁₀H₉O₂C₄H₈]^–) with metal acetylenides, diethyl malonate, ethyl acetoacetate, triethyl orthoformate, acetylacetone, and malonodinitrile were studied. The reactions were shown to be accompanied with substituent ring opening and attachment of the corresponding pendant functional group. The obtained compounds were characterized by various physicochemical methods (IR and polynuclear NMR spectroscopy, ESI mass spectrometry).     

Non-isothermal kinetics of thermal decomposition of NH<Subscript>4</Subscript>ZrH(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·H<Subscript>2</Subscript>O

Nanocrystalline NH₄ZrH(PO₄)₂·H₂O was synthesized by solid-state reaction at low heat using ZrOCl₂·8H₂O and (NH₄)₂HPO₄ as raw materials. X-ray powder diffraction analysis showed that NH₄ZrH(PO₄)₂·H₂O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH₄ZrH(PO₄)₂·H₂O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration of the protonated phosphate groups, and the formation of orthorhombic ZrP₂O₇. In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps' mass losses of NH₄ZrH(PO₄)₂·H₂O and crystallization of ZrP₂O₇ were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated with the NH₄ZrH(PO₄)₂·H₂O thermal decomposition and crystallization of ZrP₂O₇ were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol⁻¹, respectively. Dehydration of the crystal water of NH₄ZrH(PO₄)₂·H₂O could be due to multi-step reaction mechanisms: deamination of NH₄ZrH(PO₄)₂ and intramolecular dehydration of the protonated phosphate groups from Zr(HPO₄)₂ are simple reaction mechanisms.     

Interaction of [В<Subscript>10</Subscript>H<Subscript>10</Subscript>]<Superscript>2–</Superscript> and [В<Subscript>12</Subscript>H<Subscript>12</Subscript>]<Superscript>2–</Superscript> with nitro compounds

The interaction of the [B₁₀H₁₀]^2– and [B₁₂H₁₂]^2– anions with aliphatic and aromatic nitro compounds (RNO₂, where R = Et, n-Pr, i-Pr, tert-Bu, Ph) has been studied under irradiation with visible and UV light. It has been shown that, depending on the reaction conditions, both mono- and disubstituted nitro-closo-decaborates can be selectively obtained in yields up to 50%.     

Experimental Determination of the Isotherm at 15°C of the System Mg<Superscript>2+</Superscript>/Cl<Superscript>−</Superscript>, SO<Subscript>4</Subscript><Superscript>2</Superscript>–H<Subscript>2</Subscript>O

Summary.  The diagram of the ternary system Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O was established at 15°C by means of analytical and conductimetric measurements. Three compounds were found in this diagram, which are MgSO₄·6H₂O, MgSO₄·7H₂O, and MgCl₂·6H₂O. The solubility field of MgSO₄·7H₂O is important whereas those of MgSO₄·6H₂O and MgCl₂·6H₂O are small. The compositions (mass-%) of the two invariant points determined by the two methods are: MgSO₄:MgCl₂=2.73:33.80 and MgSO₄: MgCl₂=3.38:28.91. Both the measured and the calculated isotherm at 15°C have been used for modelling of the diagram Mg²⁺/Cl⁻, SO₄ ²⁻–H₂O between 0 and 35°C. The polythermal invariant point was approximately located between 15 and 10°C.  Corresponding author. E-mail: ariguib@planet.tn Received October 16, 2002; accepted (revised) December 3, 2002 Published online April 24, 2003 RID="a" ID="a" Dedicated to Prof. Dr. Heinz Gamsj?ger on the occasion of his 70^th birthday     

Reactions of [NH<Stack><Subscript>3</Subscript><Superscript>+·</Superscript></Stack>, H<Subscript>2</Subscript>O] with carbonyl compounds: A McLafferty rearrangement within a complex?

The reactions of the water solvated ammonia radical cation [NH(3)(+*), H(2)O] with a variety of aldehydes and ketones were investigated. The reactions observed differ from those of low energy aldehydes and ketones radical cations, although electron transfer from the keto compound to ionized ammonia is thermodynamically allowed within the terbody complexes initially formed. The main process yields an ammonia solvated enol with loss of water and an alkene. This process corresponds formally to a McLafferty fragmentation within a complex. With aldehydes, another reaction can take place, namely the transfer of the hydrogen from the CHO group to ammonia, leading to the proton bound dimer of ammonia and water, and to the NH(4)(+) cation. Comparison between the available experimental results leads to the conclusion that the McLafferty fragmentation occurs within the terbody complex initially formed, with no prior ligand exchange, the water molecule acting as a spectator partner.     

Hydration of CBr<Subscript>3</Subscript>COOH molecules and CBr<Subscript>3</Subscript>CO<Stack><Subscript>2</Subscript><Superscript>–</Superscript></Stack> anions in aqueous solutions

The optimal structures and the vibrational frequencies of H-bonded complexes formed from one-two CBr₃COOH molecules or the CBr₃CO ₂ ^– anion with water molecules are calculated by density functional theory (B3LYP/6-31++G(d,p)). The comparison of the obtained results with the known Raman spectra of the CBr₃COOH–H₂O and NaCBr₃CO ₂ ^– ·H₂O solutions (with component molar ratios of ≤1:16) shows that they include stable hydrates: CBr₃COOH·H₂O and CBr₃CO ₂ ^– ·(H₂O)₆. The first one has a cyclic form, and the second has a cubic globular form. The vibrational band frequencies of the CBr₃COOH molecule and the CBr₃CO ₂ ^– anion in the spectra of both solutions are almost completely determined by the mutual arrangement of units in these hydrates.     

Preparation of nano-SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack>/TiO<Subscript>2</Subscript> catalyst and its application in esterification of sebacic acid with 2-ethyl hexanol

A pure anatase phase nano-SO₄²⁻ /TiO₂ catalysts were synthesized and their catalytic activities were tested. Nano-SO₄²⁻/TiO₂ shows high activity and effective re-usable when used as basic catalysts for the synthesis of dioctyl sebacate.     

Synthesis and physicochemical study of the PMo<Subscript>11</Subscript>(TiO)O<Stack><Subscript>39</Subscript><Superscript>5−</Superscript></Stack> heteropolyanion

Procedures were developed for the synthesis of the guanidinium (Gua) and tetrabutylammonium (TBA) salts of 11-molybdotitano(IV)phosphate heteropolyanion (MTPH) from solutions with the stoichiometric ratio P: Mo = 1: 11 and in excess of titanium(IV) ions, Ti: P ≥ 1.5, at pH 1.85–1.90. MTPH was isolated as the (Gua)₅PMo₁₁(TiO)O₃₉ and (TBA)₅PMo₁₁(TiO)O₃₉ salts. The composition and formula of MTPH were established by chemical analysis, electronic absorption spectroscopy in the visible region of the oxidized and reduced MTPH forms, IR spectroscopy, and ³¹P NMR. H₅PMo₁₁(TiO)O₃₉, obtained by ion exchange of the Gua salt in an aqueous-organic medium, is a strong pentabasic acid. MTPH reacts with H₂O₂ to form a peroxo complex with limited stability in an aqueous solution. In aqueous-organic media, the peroxo complex is more stable. In acetonitrile, MTPH persists for several days.     

Identification of Anionic Supramolecular Complexes of Sulfonamide Receptors with Cl<Superscript>−</Superscript>, NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> by APCI-MS

As part of a mass spectrometric investigation of the binding properties of sulfonamide anion receptors, an atmospheric pressure chemical ionization mass spectrometric (APCI-MS) method involving direct infusion followed by thermal desorption was employed for identification of anionic supramolecular complexes in dichloromethane (CH₂Cl₂). Specifically, the dansylamide derivative of tris(2-aminoethyl)amine (tren) (1), the chiral 1,3-benzenesulfonamide derivatives of (1R,2S)-(+)-cis-1-amino-2-indanol (2), and (R)-(+)-bornylamine, (3), were shown to bind halide and nitrate ions in the presence of (n−Bu)₄N⁺X⁻ (X⁻ = Cl⁻, NO₃⁻, Br⁻, I⁻). Solutions of receptors and anions in CH₂Cl₂ were combined to form the anionic supramolecular complexes, which were subsequently introduced into the mass spectrometer via direct infusion followed by thermal desorption. The anionic supramolecular complexes [M+X]⁻, (M=1–3, X⁻=Cl⁻, NO₃⁻, Br⁻, I⁻) were observed in negative mode APCI-MS along with the deprotonated receptors [M−H]⁻. Full ionization energy of the APCI corona pin (4.5 kV) was necessary for obtaining mass spectra with the best signal-to-noise ratios.