Insertion of an Oxygen Atom between Tellurium Atoms upon Oxidation of a Diaryl Telluride with NOBF4 or (CF3SO2)2O/O2: Dicationic Bis[diaryltellurium(IV)] Oxide

NO and O ₂ molecules are the source of the oxygen atom for dicationic µ-oxo(diaryltellurium) dimers 2 (X=BF₄⁻, CF₃SO₃⁻), which form upon chemical oxidation of 1 with NOBF₄ (method A) or (CF₃SO₂)₂O/O₂ [method B, Eq. (a)]. The fate of the nitrogen atom of the oxidizing agent NOBF₄ remains uncertain at this stage.     

Donor properties of the vanadyl ion: reactions of vanadyl salicylaldimine beta-ketimine and acetylacetonato complexes with groups 14 and 15 Lewis acids

Reactions of organosilicon, -germanium, -tin, -lead, -antimony, and -tin tetrahalide Lewis acids with VO(salen) [H(2)salen = N,N'-bis(salicylidene)ethane-1,2-diamine], related vanadyl salicylaldimines, VO(acacen) [H(2)acacen = N,N'-bis(acetylacetonato)ethane-1,2-diamine], and VO(acac)(2) (acac = acetylacetonato) have been investigated, revealing VO(salen) and VO(acacen) to be significantly stronger vanadyl donors than VO(acac)(2). The vanadyl donor strength of VO(salen) significantly diminishes with the introduction of electron-withdrawing substituents on the salicylaldimine ligand, and the introduction of methyl substituents on the imine carbon atoms can result in a preference for phenolic over vanadyl oxygen donation. Vanadyl donation results in an increase in the vanadyl bond length, while it leaves the distance of vanadium from the basal plane relatively unaffected. Coordination of water trans to a vanadyl oxygen that is involved in a donor bond to tin or lead has little or no effect on the vanadyl bond length but results in a marked movement of vanadium toward the basal plane and a decrease of the V=O-D (D = Sn or Pb) bond angle by as much as 13 degrees, the latter reflecting a loss of multiple bond character of the vanadyl bond. Formation of a vanadyl donor bond results in a decrease in both the vanadyl stretching frequency (infrared spectrum) and energy of the e(pi) <-- b(2) transition (electronic spectrum), the latter being intimately related to the strength of the vanadyl donor bond, while the shift of the b(1) <-- b(2) transition to higher or lower energy is relatively small for vanadyl salicylaldimine and beta-ketimine complexes. Donation through the phenolic oxygen atoms results in an increase in the vanadyl stretching frequency and energy of the e(pi) <-- b(2) transition, which can result in e(pi) <-- b(2)/b(1) <-- b(2) energy crossover.     

Vanadium (III), oxovanadium (IV) and oxovanadium (V) trifluoro-methanesulfonates

V(SO₃CF₃)₃, VO(SO₃CF₃)₂ and VO(SO₃CF₃)₃ have been prepared by reacting V(O₂CCF₃)₃, VO(O₂CCF₃)₂ and VOC1₃ with HSO₃CF₃. The i.r. data suggest a bridging bidentate nature for SO₃CF₃ groups. The diffuse reflectance spectrum of V(SO₃CF₃)₃ suggests hexacoordination of vanadium, whilst that of VO(SO₃CF₃)₂ is comparable to either five or six coordinated oxovanadium (IV) systems. The magnetic moments of V(SO₃CF₃)₃ and VO(SO₃CF₃)₂ are slightly lower than the spin-only values. Thermal decomposition of these triflates is simple. All the three triflates form coordination complexes with pyridine, 2, 2′-bipyridyl and triphenylphosphine oxide.     

A NEW PERSPECTIVE ON VANADYL TARTRATE DIMERS. PART II. STRUCTURE AND SPECTROSCOPIC PROPERTIES OF CALCIUM VANADYL TARTRATE TETRAHYDRATE

Abstract

The calcium vanadyl tartrate complex [Ca(VO)(d,l-C₄H₂O₆)(H₂O)₄] has been synthesized and characterized by spectroscopic methods. Its crystal structure was solved by X-ray methods. The compound is monoclinic, space group P2₁/c, with a = 8.0282(5), b = 17.1568(8), c = 7.6113(3)Å, β = 94.269(4)° and Z = 4. The structure consists of centrosymmetric vanadyl tartrate dimers, [(VO)(d,l-C₄H₂O₆)]₂ ^4-, and calcium cations placed between them. As a result, dimers form chains in the [101] direction. Neighbouring chains are linked by the coordination of the calcium ion to the oxygen atom of a vanadyl group of a different chain, thus forming a two-dimensional structure. Different layers are linked by hydrogen bonds. Spectroscopic studies show the existence of intra-dimeric interactions between vanadium atoms.     

Synthesis,characterization and α‐amylase and α‐glucosidase inhibition studies of novel vanadyl chalcone complexes

A series of chalcone ligands and their corresponding vanadyl complexes of composition [VO (L^I–IV)₂(H₂O)₂]SO₄ (where L^I = 1,3‐Diphenylprop‐2‐en‐1‐one, L^II = 3‐(2‐Hydroxy‐phenyl)‐1‐phenyl‐propenone, L^III = 3‐(3‐Nitro‐phenyl)‐1‐phenyl‐propenone, L^IV = 3‐(4‐Methoxy‐phenyl)‐1‐phenyl‐propenone) have been synthesized and characterized using various spectroscopic (Fourier‐transform infrared, electrospray ionization mass, nuclear magnetic resonance, electron paramagnetic resonance, thermogravimetric analysis, vibrating sample magnetometer) and physico‐analytic techniques. Antidiabetic activities of synthesized complexes along with chalcones were evaluated by performing in vitro and in silico α‐amylase and α‐glucosidase inhibition studies. The obtained results displayed moderate to significant inhibition activity against both the enzymes by vanadyl chalcone complexes. The most potent complexes were further investigated for the enzyme kinetic studies and displayed the mixed inhibition for both the enzymes. Further, antioxidant activity of vanadyl chalcone complexes was evaluated for their efficiency to release oxidative stress using 2,2‐diphenyl‐1‐picryl‐hydrazyl‐hydrate assay, and two complexes (Complexes 2 and 4 ) have demonstrated remarkable antioxidant activity. All the complexes were found to possess promising antidiabetic and antioxidant potential.     

Synthesis and properties of (VO)<Subscript>0.09</Subscript>V<Subscript>0.18</Subscript>Mo<Subscript>0.82</Subscript>O<Subscript>3</Subscript> · 0.54H<Subscript>2</Subscript>O microrods

The (VO)_0.09V_0.18Mo_0.82O₃ · 0.54H₂O microrods of hexagonal symmetry system with the unit cell parameters a = 10.586 Å and c = 3.698 Å were obtained for the first time under hydrothermal conditions (T = 160°C, τ = 30?50 h). Particles were 1–2 μm in diameter and up to 45 μm in length. The compound is thermally stable up to 469°C. The core-electron Mo3d, V2p, and O1s and valence-band X-ray photoelectron spectra and IR spectra of the samples were studied. The molybdenum atoms in the complex oxide have the oxidation state Mo⁶⁺. The vanadium atoms introduced into the h-MoO₃ lattice in molybdenum positions have the oxidation state V⁵⁺. Approximately one-third of vanadium atoms as vanadyl ions (VO)²⁺ are located in the channels of h-MoO₃ lattice, thus stabilizing the latter.     

Tunning CO2 Separation Performance of Ionic Liquids through Asymmetric Anions

This work aims to explore the gas permeation performance of two newly-designed ionic liquids, [C₂mim][CF₃BF₃] and [C₂mim][CF₃SO₂C(CN)₂], in supported ionic liquid membranes (SILM) configuration, as another effort to provide an overall insight on the gas permeation performance of functionalized-ionic liquids with the [C₂mim]⁺ cation. [C₂mim][CF₃BF₃] and [C₂mim][CF₃SO₂C(CN)₂] single gas separation performance towards CO₂, N₂, and CH₄ at T = 293 K and T = 308 K were measured using the time-lag method. Assessing the CO₂ permeation results, [C₂mim][CF₃BF₃] showed an undermined value of 710 Barrer at 293.15 K and 1 bar of feed pressure when compared to [C₂mim][BF₄], whereas for the [C₂mim][CF₃SO₂C(CN)₂] IL an unexpected CO₂ permeability of 1095 Barrer was attained at the same experimental conditions, overcoming the results for the remaining ILs used for comparison. The prepared membranes exhibited diverse permselectivities, varying from 16.9 to 22.2 for CO₂/CH₄ and 37.0 to 44.4 for CO₂/N₂ gas pairs. The thermophysical properties of the [C₂mim][CF₃BF₃] and [C₂mim][CF₃SO₂C(CN)₂] ILs were also determined in the range of T = 293.15 K up to T = 353.15 K at atmospheric pressure and compared with those for other ILs with the same cation and anion’s with similar chemical moieties.     

Reaction of [VO(OPr)3] with hexamethyldisylthiane in the presence of β-diketones

The reaction of [VO(OPr)₃] (Pr is n-propyl) with hexamethyldisylthiane Me₃SiSSiMe₃ in the presence of β-diketones (acetylacetone (HAcac), hexafluoroacetylacetone (Hfac), and dipivaloylmethane (Dpm)), is studied. In all cases, vanadium(IV) and vanadium(III) β-diketonate complexes of different types are formed. New crystalline modification [V(Acac)₃] is obtained in the reaction with HAcac. The mixedligand vanadium(III) complex of the composition [V₂(Hfac)₂(μ-OPr)]₂ is formed with Hfac. In the presence of Dpm, the known vanadium(IV) complex [V₂O₂(Dpm)₂(μ-OPr)₂] is obtained in which two vanadyl groups VO²⁺ are linked by two bridging propoxy groups. The structures of all products are determined by X-ray diffraction analysis.     

Dimethyl-N-Halogenamine,ihre Ammoniumsalze und Bortrihalogenid-Addukte

Dimethyl-N-Halogenoamine, their Ammonium Salts and Borontrihalide Adducts The preparation and vibrational spectra of (CH₃)₂NHCl⁺X^? (X^? = CF₃SO₃^? I , SO₃F^? II , SO₃Cl^? III , BCl₄^? IV ), and (CH₃)₂NHBr⁺CF₃SO₃^? V as well as the adducts (CH₃)₂NCl · S (S = BF₃ VI , BCl₃ VII , BBr₃ VIII ) and (CH₃)₂NBr · BF₃ IX are reported. The crystal structure of VII has been determined from three-dimensional diffractometer data at ?100°C. The Cl atom and one methyl group in the dimethyl-N-chloroamino group show disorder. The structural data are: B? Cl 183(2) pm, B? N 167(3) pm, N? C 152(3) pm (distances to disordered positions are not included).     

Nanoparticle supported,magnetically separable vanadium complex as catalyst for selective oxidation of sulfides

A magnetically recyclable vanadium(V) catalyst was synthesized by covalent anchoring of VO(salen)Cl on silica-coated Fe₃O₄ nanoparticles. This straightforward preparation yields magnetically separable Fe₃O₄@SiO₂@VO(salen) nanoparticles with high vanadium loading. These nanoparticles were efficient catalysts for selective oxidation of sulfides to corresponding sulfoxides with urea hydrogen peroxide in excellent yields. Leaching and recycling experiments revealed that the nanocatalyst can be applied for nearly complete oxidation of sulfides for at least five successive cycles.     

The reaction of boron trihalides with CF3Sn(CH3)3 in the presence of trimethylamine

The reaction of CF₃Sn(CH₃)₃ with BCl₃ and BBr₃ in the presence of trimethylamine has been investigated. The volatile adducts CF₂XBF₂·N(CH₃)₃ (X = F, Cl and Br) have been isolated from the complex reaction mixture while the anions BF^?₄, CF₂XBF^?₃, CF₃BF₂CF₂X^? and (CF₂X)₂BF^?₂ have been identified in the residue. [(CH₃)₃NH][CF₂ClBF₃] has been isolated. The formation of the CF₂XB derivatives is likely to occur via CF₂ insertion, which is promoted by the presence of N(CH₃)₃. NMR, IR, Raman and mass spectra of the novel fluoromethyl borane derivatives are reported.     

Synthesis and characterization of new <Emphasis Type="Italic">vic</Emphasis>-dioximes and their metal complexes with Cu(II), Ni(II), and Co(II) salts

4-Acetyldiphenyl sulfide and 4,4′-diacetyldiphenyl sulfide were synthesized from diphenyl sulfide and acetyl chloride in the presence of AlCl₃ as catalyst in the Friedel-Crafts reaction. Subsequently, the ketooxime and glyoxime derivatives were also prepared. The metal complexes of the glyoximes, such as copper, nickel, and cobalt complexes were prepared. The BF²⁺ capped Ni(II) mononuclear complex of 4-thiophenoxyphenylglyoxime was prepared. The structures of these ligands were identified by FT-IR, ¹H NMR, and ¹³C NMR spectral data and elemental analysis. The structures of the complexes were identified by FT-IR, elemental analysis, and magnetic measurements. The text was submitted by the authors in English.     

FT-IR and FT-Raman spectroscopy study of di-urethanesil hybrids doped with Mg(CF3SO3)2

In the present work di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrids (di-urethanesils) incorporating magnesium triflate (Mg(CF₃SO₃)₂) with 100 ≥ n ≥ 2 (where n, composition, is the molar ratio of oxyethylene repeat units per Mg²⁺ ion) have been characterized by Fourier transform infrared and Raman spectroscopy to elucidate the Mg²⁺/POE, Mg²⁺/urethane, Mg²⁺/CF₃SO₃⁻ and hydrogen bonding interactions. The Mg²⁺ ions bond to POE chains and to the carbonyl oxygen atoms of the urethane linkages over the whole range of salt content studied. A crystalline POE/Mg(CF₃SO₃)₂ complex of unknown stoichiometry is formed at n = 5. “Free” and weakly coordinated CF₃SO₃⁻ ions are present in all the materials examined. Contact ion pairs emerge at n ≤ 20 and higher ionic aggregates appear at n ≤ 5.     

Darstellung,Ramanspektren und Kristallstrukturen von V2O3(SO4)2, K[VO(SO4)2] und NH4[VO(SO4)2]

Preparation, Raman Spectra, and Crystal Structures of V₂O₃(SO₄)₂, K[VO(SO₄)₂], and NH₄[VO(SO₄)₂] The oxo-sulfato-vanadates(V) V₂O₃(SO₄)₂, K[VO(SO₄)₂], and NH₄[VO(SO₄)₂] have been prepared as crystals suitable for X-ray structure determination. In all structures sulfate acts as an unidentate ligand only toward a single vanadium atom. The structure of V₂O₃(SO₄)₂ consists of a threedimensional network of pairs of cornershared VO₆ octahedra with one terminal oxygen atom each, and SO₄ tetrahedra. All oxygen atoms of the sulfate ions are coordinated. NH₄[VO(SO₄)₂] and K[VO(SO₄)₂] are isostructural. VO₆ octahedra with one terminal oxygen atom and pairs of sulfate tetrahedra form infinite chains by corner sharing. The chains are weakly interlinked to layers. The sulfate ions are distorted towards planar SO₃ molecules and single oxygen atoms attached to vanadium. This structural detail gives an explanation for the mechanism of the reversible reaction K[VO(SO₄)₂] ? K[VO₂(SO₄)] + SO₃ at 400°C. Raman spectra of the compounds have been recorded and interpreted with respect to their structures. Crystal data: V₂O₃(SO₄)₂, monoclinic, space group P2₁/a, a = 947.2(4), b = 891.3(3), c? 989.1(4) pm, β = 104.56(3)°, Z = 4, 878 unique data, R(R_w) = 0.039(0,033); K[VO(SO₄)₂], orthorhombic, space group P2₁2₁2₁, a = 495.3(2), b = 869.6(9), c = 1 627(1)pm, Z = 4, 642 unique data, R(R_w) = 0,11(0,10); NH₄[VO(SO₄)₂], orthorhombic, space group P2₁2₁2₁, a = 495.3(1), b = 870.0(2), c = 1 676.7(4)pm, Z = 4, 768 unique data, R(R_w) = 0.088(0.083).     

Chemically-derivatized nickel surfaces: Synthesis of a new class of stable electrode interfaces

The interactions of protonic acids (HClO₄ and CF₃SO₃H) and of alkylating agents (CF₃SO₃Et and Et₃O⁺BF₄^?) with cyclic ethers and 1,3-dioxacycloalkane s (DCA) in CH₂Cl₂ have been studied by dc polarography (DCP) and differential pulse polarography (DPP). All the reductions were irreversible and kinetically controlled. There is no indication that HClO₄ reacts with THF or OXP; with CF₃SO₃H the decrease of the signals due to the acid may indicate the formation of a product (sec. oxonium ion or ester) or it may be due merely to a modification of the mercury surface by the oxacyclic compound which produces a reduction in the kinetic current; no new signals appear.For the various DCAs with CF₃SO₃Et, 1,3-dioxepan (DXP) gave the clearest indication of reactions occurring and the signals have been assigned (tentatively) to EtDXP⁺ and to the hemiformal ester EtO(CH₂)₄OCH₂OSO₂CF₃. For 1,3-dioxolan (DXL) the picture was less clear, and there was no evidence that 1,3,6-trioxan (TXA) was alkylated.Our study of the DCA with acids gave no evidence that DXL interacts with HClO₄ or CF₃SO₃H, which is due to the exceptionally low basicity of DXL. The signals obtained with DXP and 1,3,6-trioxocan (TXC) are assigned to a molecular complex H₂A⁺-DCA, to the sec-oxonium ion HDCA⁺, and to the hemiformal ester HO(CH₂)₄OCH₂OA.It is concluded that the polarographic behaviour of all the species involved is so complicated that our original aim of distinguishing by this technique between sec. and tert. oxonium ions is not feasible.The sec. oxonium ions formed from cyclic ethers or DCA in conc. H₂SO₄, whose existence was indicated by the PMR spectra, could not be detected polarographically as their reduction potentials were outside the “potential window”.     

Reaktive hydrido-iridium(III)-komplexe mit den schwach koordinierten anionen BF4−, CF3SO3− und C4F9SO3−

Oxidative addition of HBF₄, CF₃SO₃H and C₄F₉SO₃H to trans-(Ph₃P)₂Ir(L)Cl (L = CO, N₂) gives the highly reactive irridium(III) complexes (Ph₃P)₂Ir(L)(Cl)(H)(X) (X = BF₄, CF₃SO₃, C₄F₉SO₃), in which the anion X can be easily substituted by σ- and π-donors. In the dinitrogen complex (Ph₃P)₂Ir(N₂)(Cl)(H)(FBF₃) (2a) both the N₂ and BF₄ ligands are replaced by valinate, diethyldithiocarbamate or tertiary phosphines, respectively. 2a catalyzes the hydrogenation of cyclohexene and the isomerisation of 1,5-cyclooctadiene.     

A Design Strategy for Single‐Stranded Helicates using Pyridine‐Hydrazone Ligands and PbII

The reactions of py‐hz ligands ( L1–L5 ) with Pb(CF₃SO₃)₂?H₂O resulted in some rare examples of discrete single‐stranded helical Pb^II complexes. L1 and L2 formed non‐helical mononuclear complexes [Pb L1 (CF₃SO₃)₂]?CHCl₃ and Pb L2 (CF₃SO₃)₂][Pb L2 CF₃SO₃]CF₃SO₃?CH₃CN, which reflected the high coordination number and effective saturation of Pb^II by the ligands. The reaction of L3 with Pb^II resulted in a dinuclear meso‐helicate [Pb₂ L3 (CF₃SO₃)₂Br]CF₃SO₃?CH₃CN with a stereochemically‐active lone pair on Pb^II. L4 directed single‐stranded helicates with Pb^II, including [Pb₂ L4 (CF₃SO₃)₃]CF₃SO₃?CH₃CN and [Pb₂ L4 CF₃SO₃(CH₃OH)₂](CF₃SO₃)₃?2 CH₃OH?2 H₂O. The acryloyl‐modified py‐hz ligand L5 formed helical and non‐helical complexes with Pb^II, including a trinuclear Pb^II complex [Pb₃ L5 (CF₃SO₃)₅]CF₃SO₃?3CH₃CN?Et₂O. The high denticity of the long‐stranded py‐hz ligands L4 and L5 was essential to the formation of single‐stranded helicates with Pb^II.     

Ionic complex of Vanadyl(IV) in the polymerization of 2-hydroxyethyl methacrylate as probed by EPR

The vanadyl ionic complex VO(DMSO)₅(ClO₄)₂ (I) exhibits high catalytic activity in the polymerization of 2-hydroxyethyl methacrylate (HEMA). The changes in the vanadium oxidation state during polymerization under argon and in the presence of oxygen were studied by EPR. Under aerobic conditions, the HEMA chain propagation radical was detected; this indicates the presence of a radical chain polymerization pathway caused by the ability of I to perform one-electron reduction of molecular O₂. The radical generation rate is controlled by the initial concentration of I: its increase results in the formation of inactive species, presumably, μ-peroxo complexes V^v-O-O-V^v. It was shown by kinetic methods that the radical-chain pathway initiated by the reaction of I with O₂ is not crucial in the HEMA polymerization.     

Synthesis,characterization, crystal structure determination,catalytic activity and thermal study of a new oxidovanadium(IV) Schiff base complex: production of V2O5 nano-particles

A new oxidovanadium(IV) Schiff base complex, VOL₂ (1), containing furfuryl pendant group was synthesized by the reaction of the related bidentate O, N-type Schiff base ligand and VO(acac)₂ in the ratio of 2:1 in methanol in the reflux conditions. The Schiff base ligand and its vanadyl complex were characterized by ¹H-NMR and FT-IR spectra and elemental analysis. The crystal structure of 1 was also determined the single-crystal X-ray analysis. It showed that the metal center located in a distorted tetragonal pyramidal (N₂O₃) geometry in which the two bidentate Schiff base ligands were coordinated to the vanadium(IV) ion in four equatorial positions, and one oxygen atom in its axial position. The catalytic activity of the vanadyl Schiff base complex was elucidated in the epoxidation of cyclooctene as a model substrate. Different reaction parameters were investigated in this reaction and the results showed that it was an effective and selective catalyst in these optimal conditions. Thermogravimetric analysis of 1 showed that it was decomposed in two stages by losing two methoxy groups and other organic residuals, respectively, in the temperature range of 253–532 °C. In addition, the vanadyl Schiff base complex (1) was thermally decomposed in air at 660 °C and the XRD pattern of the obtained solid showed the formation of the V₂O₅ nano-particles with the average size of 52 nm.     

Donor and acceptor properties of the solvents tetrahydrofuran and tetrahydrothiophene

The donor and acceptor properties of tetrahydrofuran and tetrahydro-thiophene were evaluated by means of electrochemical and spectroscopic methods. Polarographic and cyclovoltammetric data for LiClO₄, NaClO₄, KClO₄, RbClO₄, CsClO₄, Ba(ClO₄)₂, AgCF₃SO₃, TlClO₄, Zn(CF₃SO₃)₂, Cd(CF₃SO₃)₂, Cu(CF₃SO₃)₂, Pb(CF₃SO₃)₂, Mn(CF₃SO₃)₂, Co(CF₃SO₃)₂, Ni(ClO₄)₂·2H₂O, oxygen, perylene, ferrocene, and bis(biphenyl)chromium tetraphenylborate in tetrahydrofuran and of TlClO₄, CuCF₃SO₃, Pb(CF₃SO₃)₂, Cd(CF₃SO₃)₂, oxygen, ferrocene and bis(biphenyl)chromium tetraphenylborate in tetrahydrothiophene together with the potentials of the Ag/0.01 M Ag⁺-ion electrodes in these two solvents are given. Molar Gibbs (free) energies for the transfer from acetonitrile into tetrahydrofuran for Na⁺, K⁺, Rb⁺, Ag⁺, Tl⁺, Zn²⁺, Cd²⁺, and Pb²⁺, and for the transfer into tetrahydrothiophene for Ag⁺, Cu⁺, Tl⁺, Cd²⁺, and Pb²⁺ were calculated from these data. Visible spectra were obtained for the solvatochromic dyes acetylacetonato(N,N,N,N,-tetramethylethylenediamine) copper(II) perchlorate and for 2,6-diphenyl-4-(2,4,6-triphenyl-l-pyridinio)phenoxide, which served as secondary standards to obtain donor and acceptor numbers. The changes in half-wave potentials of the cations vs. bis(biphenyl)chromium(I)/(0) and the Gibbs energies of transfer are discussed on basis of hard and soft donor properties of these two solvents.