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Vanadium
Terms modified by Vanadium Selected AbstractsVANADIUM: Eight-fold Price IncreaseAFRICA RESEARCH BULLETIN: ECONOMIC, FINANCIAL AND TECHNICAL SERIES, Issue 4 2010Article first published online: 4 JUN 2010 No abstract is available for this article. [source] Binding of Oxovanadium(IV) to Tripeptides Containing Histidine and Cysteine Residues and Its Biological Implication in the Transport of Vanadium and Insulin-Mimetic CompoundsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2005Eugenio Garribba Abstract The complexation of VIVO ion with three tripeptides of biological importance containing L -histidine or L -cysteine (HisGlyGly, GlyGlyHis and GlyGlyCys) has been studied. This study was performed in aqueous solution by the combined application of potentiometric and spectroscopic (electronic absorption and EPR) techniques. The results indicate that these oligopeptides, if a ligand-to-metal molar ratio of 10 or 15 is used, can keep VIVO ion in solution until the deprotonation of the amide group with the donor set (NH2, CO, Nimax) for HisGlyGly or (COO,, CO) for GlyGlyHis and GlyGlyCys. In all the systems, at pH values around neutrality, a VOLH,2 species is formed with an (NH2, N,, N,, COO,) donor set for HisGlyGly, (NH2, N,, N,, Nim) for GlyGlyHis and (NH2, N,,N,, S,) for GlyGlyCys. These species, and those with onedeprotonated amide group coordinated to the VIVO ion, can be detected by EPR spectroscopy. The N,(amide) contribution to the hyperfine coupling constant along the z axis, Az, depends on the total charge of the donor atoms in the equatorial plane. The participation of albumin in the transport of vanadium and insulin-mimetic VIVO compounds is reconsidered based on these results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Stabilizing Factors for Vanadium(IV) in Amavadin,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2007Ton Hubregtse Abstract Six secondary N -hydroxy amino acids (amavadin-based ligands) have been prepared through a strategy with nitrone reduction as its key step. Two of these amino acids are the new amavadin ligand analogues 4a and 4b containing either a phenyl or a benzyl group in combination with a small backbone substituent. In addition, the monoester 5 of the amavadin ligand as well as three N -alkylated N -hydroxy aminoacids 6 were prepared. Complexation studies with the new tri- and bidentate ligands using HRMS revealed that only amavadin and its two analogues with ligands 4a and 4b are stable in aqueous and aerobic environments and that the complexation of vanadium(IV) with ligands 5 and 6 does not lead to air-stable vanadium(IV) non-oxo compounds. An interesting spin-off of the synthetic work on nitrones is an effective and easily applicable method for the synthesis of racemic N -hydroxy amino acid esters. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Vanadium-induced apoptosis of HaCaT cells is mediated by c-fos and involves nuclear accumulation of clusterinFEBS JOURNAL, Issue 14 2009Soultana Markopoulou Vanadium exerts a variety of biological effects, including antiproliferative responses through activation of the respective signaling pathways and the generation of reactive oxygen species. As epidermal cells are exposed to environmental insults, human keratinocytes (HaCaT) were used to investigate the mechanism of the antiproliferative effects of vanadyl(IV) sulfate (VOSO4). Treatment of HaCaT cells with VOSO4 inhibited proliferation and induced apoptosis in a dose-dependent manner. Inhibition of proliferation was associated with downregulation of cyclins D1 and E, E2F1, and the cyclin-dependent kinase inhibitors p21Cip1/Waf1 and p27Kip1. Induction of apoptosis correlated with upregulation of the c-fos oncoprotein, changes in the expression of clusterin (CLU), an altered ratio of antiapoptotic to proapoptotic Bcl-2 protein family members, and poly(ADP-ribose) polymerase-1 cleavage. Forced overexpression of c-fos induced apoptosis in HaCaT cells that correlated with secretory CLU downregulation and upregulation of nuclear CLU (nCLU), a pro-death protein. Overexpression of Bcl-2 protected HaCaT cells from vanadium-induced apoptosis, whereas secretory CLU overexpression offered no cytoprotection. In contrast, nCLU sensitized HaCaT cells to apoptosis. Our data suggest that vanadium-mediated apoptosis was promoted by c-fos, leading to alterations in CLU isoform processing and induction of the pro-death nCLU protein. [source] Matrix metalloproteinases 2 and 9 in central nervous system and their modification after vanadium inhalationJOURNAL OF APPLIED TOXICOLOGY, Issue 6 2008L. Colín-Barenque Abstract Vanadium (V) derivatives are well-known environmental pollutants and its toxicity has been related with oxidative stress. Toxicity after vanadium inhalation on the substantia nigra, corpus striatum, hippocampus and ependymal epithelium was reported previously. The purpose of this study was to analyse the role of matrix metalloproteinases 2 (MMP-2) and 9 (MMP-9) in the changes observed in brain tissue after chronic V inhalation. Mice were exposed to vaporized, vanadium pentoxide 0.02 m in deionized water for 1 h twice a week, and killed at 1 h, 1, 2 and 4 weeks after exposure. The brain was removed and the olfactory bulb, prefrontal cortex, striatum and hippocampus were dissected and the MMP content was obtained by zymography. The results showed that MMP-9 increased in all the structures at the end of the exposure, although in the hippocampus this increment was evident after 1 week of exposure. When MMP-2 was analysed in the olfactory bulb and prefrontal cortex it remained unchanged throughout the whole exposure, while in the hippocampus it increased at week 4, while in the striatum MMP-2 increased from the second week only, through the whole experiment. These results demonstrate that V increased MMPs in different structures of the CNS and this change might be associated with the previously reported modifications, such as dendritic spine loss and neuronal cell death. The modifications in MMPs could be related with blood,brain barrier (BBB) disruption which was reported previously. Oxidative stress might also be involved in the activation of these gelatinases as part of the different mechanisms which take place in V toxicity in the CNS. Copyright © 2007 John Wiley & Sons, Ltd. [source] Preparation of Molybdenum, Vanadium, and Tungsten Oxide Thin Films from Self-Assembly Deposited Polyoxometalate,Alkylamine-Layered Hybrid FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2007Tetsuya Kida A novel, simple, and efficient route for preparing MoO3, V2O5, and WO3 films has been developed from layered polyoxometallate (POM)-alkylamine hybrid films by calcination. The highly ordered hybrid films were self-assembly deposited in a one-step process using clear precursor POM solutions, prepared by reacting layered MoO3, V2O5, and WO3·H2O powders with hexylamine in the presence of water. The morphology of the resulting films can be tuned by removing the intercalated hexylamine molecules from the as-prepared hybrid films through UV irradiation before calcination. [source] Cages with Tetrahedron-Like Topology Formed from the Combination of Cyclotricatechylene Ligands with Metal Cations,ANGEWANDTE CHEMIE, Issue 16 2010Brendan Viel Platz: Anionische tetraedrische Aggregate, gebildet durch Kombination von Cyclotricatechylen-Anionen mit Übergangsmetallionen wie Vanadium (siehe Bild), umschließen große Hohlräume, die Alkalimetallionen und Lösungsmittelmoleküle aufnehmen können. Anionische Einheiten mit geeigneten Metallzentren lassen sich zu hoch symmetrischen Koordinationspolymeren verknüpfen (V,blau, O,rot, C,schwarz). [source] A new whitlockite, Ca8.42Na1.16V(PO4)7ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2006Alexander A. Tsirlin Single crystals of a new complex phosphate, calcium sodium vanadium phosphate, Ca8.42Na1.16V(PO4)7, have been grown from a melt under an inert atmosphere. The crystal structure has rhombohedral (R3c) symmetry and belongs to the whitlockite structure type. Vanadium(III) ions occupy nearly regular octahedral sites (M5 with 3 point symmetry), which share corners with six PO4 tetrahedra to form isolated units. The calcium ions occupy eight- and nine-coordinated sites. The sodium ions partially occupy one octahedral position and share one nine-coordinated position with a Ca atom. [source] Vanadium , lebenswichtiges SpurenelementCHEMIE IN UNSERER ZEIT (CHIUZ), Issue 5 2010Article first published online: 6 OCT 2010 Für höhere Lebewesen , und damit auch für den Menschen , ist Vanadium ein wichtiges Spurenelement, das in der Regulation des Phosphatmetabolismus eine entscheidende Rolle spielt. Hierauf basiert seine potenzielle Verwendung in der Behandlung der Zuckerkrankheit (Diabetes mellitus). Einige phylogenetisch ältere Organismengruppen, darunter vor allem die zu den Tunikaten gehörenden Seescheiden (Ascidiaceae), speichern erhebliche Mengen Vanadium aus bis heute unbekannten Gründen. Noch ältere Organismen verwenden Vanadium als zentrales Metall in Enzymen. Dazu gehören Halogenid-oxidierende Enzyme in Meerestangen und primitiven Pilzen, und bakterielle Enzyme, die in der Lage sind, den Luftstickstoff reduktiv zu fixieren. [source] ChemInform Abstract: Electronic Structure and Spin Exchange Interactions in Na2V3O7: A Vanadium(IV) Oxide Nanotubular PhaseCHEMINFORM, Issue 36 2009Antonio Rodriguez-Fortea Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Syntheses and Crystal Structures of New Vanadium(IV) Oxyphosphates M(VO)2(PO4)2 with M: Co, Ni.CHEMINFORM, Issue 23 2009S. Kaoua Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Rapid, Efficient, Room Temperature Aromatization of Hantzsch-1,4-dihydropyridines with Vanadium(V) Salts: Superiority of Classical Technique versus Microwave Promoted Reaction.CHEMINFORM, Issue 12 2009Mirela Filipan-Litvic Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: An Imido-Transfer Reaction of Aldehydes with N-Sulfinylamines Using Vanadium and Molybdenum Oxochlorides as Catalysts.CHEMINFORM, Issue 19 2008Anton A. Zhizhin Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthesis and Crystal Structure of Hg2V8O20 , The First Ternary Mercury Vanadate with Mixed-Valent Vanadium (IV/V).CHEMINFORM, Issue 2 2008Matthias Weil Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Cs+ -Selective Ion Exchange and Magnetic Ordering in a Three-Dimensional Framework Uranyl Vanadium(IV) Phosphate.CHEMINFORM, Issue 16 2007Tatiana Y. Shvareva Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Tuning the Oxidation Properties of Vanadium(V) Through Ligand Stoichiometry.CHEMINFORM, Issue 47 2006Wei Zeng Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Change in Regioselectivity in the Monoreduction of 2,4,6-Trinitrotoluene with Titanium(III) and Vanadium(II) Ions in the Presence of Iron(II) and Copper(II) Salts.CHEMINFORM, Issue 29 2006V. N. Leibzon Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis and Crystal Structure of Vanadium(III) Borophosphate, V2[B(PO4)3].CHEMINFORM, Issue 38 2004Manfred Meisel Abstract For Abstract see ChemInform Abstract in Full Text. [source] Hydroamination of Alkynes Catalyzed by Imido Complexes of Titanium and Vanadium.CHEMINFORM, Issue 32 2004Christian Lorber Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of Molybdenum and Vanadium-Based Mixed Oxide Catalysts with Metastable Structure: Easy Access to the MoVNbTe(Sb)Ox Catalytically Active Structure Using Reductant and Oxoacid.CHEMINFORM, Issue 36 2003Hideto Tsuji Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: NaV3(OH)6(SO4)2: A Kagome-Type Vanadium(III) Compound with Strong Intralayer Ferromagnetic Interactions.CHEMINFORM, Issue 31 2001Daniel Grohol Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Hydrogen-Atom Abstraction from Methane by Stoichiometric Vanadium,Silicon Heteronuclear Oxide Cluster CationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 37 2010Dr. Xun-Lei Ding Abstract Vanadium,silicon heteronuclear oxide cluster cations were prepared by laser ablation of a V/Si mixed sample in an O2 background. Reactions of the heteronuclear oxide cations with methane in a fast-flow reactor were studied with a time-of-flight (TOF) mass spectrometer to detect the cluster distribution before and after the reactions. Hydrogen abstraction reactions were identified over stoichiometric cluster cations [(V2O5)n(SiO2)m]+ (n=1, m=1,4; n=2, m=1), and the estimated first-order rate constants for the reactions were close to that of the homonuclear oxide cluster V4O10+ with methane. Density functional calculations were performed to study the structural, bonding, electronic, and reactivity properties of these stoichiometric oxide clusters. Terminal-oxygen-centered radicals (Ot.) were found in all of the stable isomers. These Ot. radicals are active sites of the clusters in reaction with CH4. The Ot. radicals in [V2O5(SiO2)1,4]+ clusters are bonded with Si rather than V atoms. All the hydrogen abstraction reactions are favorable both thermodynamically and kinetically. This work reveals the unique properties of metal/nonmetal heteronuclear oxide clusters, and may provide new insights into CH4 activation on silica-supported vanadium oxide catalysts. [source] Chemistry, Urease Inhibition, and Phytotoxic Studies of Binuclear Vanadium(IV) ComplexesCHEMISTRY & BIODIVERSITY, Issue 1 2007Rifat Ara Abstract Vanadium plays an important role in biological systems and exhibits a variety of bioactivities. In an effort to uncover the chemistry and biochemistry of vanadium with nitrogen- and oxygen-containing ligands, we report herein the synthesis and spectroscopic characterization of vanadium(IV) complexes with hydrazide ligands. Substituents on these ligands exhibit systematic variations of electronic and steric factors. Elemental and spectral data indicate the presence of a dimeric unit with two vanadium(IV) ions coordinated with two hydrazide ligands along with two H2O molecules. The stability studies of these complexes over time in coordinating solvent, DMSO, indicates binding of the solvent molecules to give [V2O2L2(H2O)2(DMSO)2]2+ (L=hydrazide ligand) and then conversion of it to a monomeric intermediate species, [VOL(DMSO)3]1+. Hydrazide ligands are inactive against urease, whereas vanadium(IV) complexes of these ligands show significant inhibitory potential against this enzyme and are found to be non-competitive inhibitors. These complexes also show low phytotoxicity indicating their usefulness for soil ureases. Structure,activity relationship studies indicate that the steric and/or electronic effects that may change the geometry of the complexes play an important role in their inhibitory potential and phytotoxicity. [source] Microstructural, thermal, and electrical properties of Bi1.7V0.3Sr2Ca2Cu3Ox glass-ceramic superconductorCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2004T. S. Kayed Abstract A glass-ceramic Bi1.7V0.3Sr2Ca2Cu3Ox superconductor was prepared by the melt-quenching method. The compound was characterized by scanning electron microscopy, x-ray diffraction, differential thermal analysis, current-voltage characteristics, transport resistance measurements, and Hall effect measurements. Two main phases (BSCCO 2212 and 2223) were observed in the x-ray data and the values of the lattice parameters quite agree with the known values for 2212 and 2223 phases. The glass transition temperature was found to be 426 °C while the activation energy for crystallization of glass has been found to be Ea = 370.5 kJ / mol. This result indicates that the substitution of vanadium increased the activation energy for the BSCCO system. An offset Tc of 80 K was measured and the onset Tc was 100 K. The Hall resistivity ,H was found to be almost field-independent at the normal state. A negative Hall coefficient was observed and no sign reversal of ,H or RH could be noticed. The mobility and carrier density at different temperatures in the range 140-300 K under different applied magnetic fields up to 1.4 T were also measured and the results are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Insulin mimetic effects of macrocyclic binuclear oxovanadium complexes on streptozotocin-induced experimental diabetes in ratsDIABETES OBESITY & METABOLISM, Issue 6 2003B. Ramachandran Aim:, The vanadium complexes so far tested for their insulin mimetic effects are either mono- or binuclear and contain only acyclic ligands. The leaching or hydrolysis of vanadyl ions from these complexes is much easier, and hence they elicit side effects. In the present study, a new binuclear macrocyclic oxovanadium complex was synthesized, and its efficacy was studied on streptozotocin (STZ)-induced diabetic rats over a period of 30 days. Methods:, The insulin mimetic effect of the complex was tested on the blood sugar level in the STZ-diabetic rats and on the activities of the carbohydrate-metabolizing enzymes present in the liver. Results:, Administration of vanadium complex to STZ-induced diabetic rats decreased blood glucose levels from hyperglycaemic to normoglycaemic when compared to diabetic rats. The activity of carbohydrate-metabolizing enzymes such as hexokinase, glucose-6-phosphate dehydrogenase, glycogen synthase and glycogen content were increased to near normal in vanadium complex-administered diabetic rats. The biochemical studies such as assay of blood urea and glutamate oxaloacetate transaminases revealed that the complex is not toxic to the system. Conclusion:, The nontoxic nature of this complex may be due to the presence of the vanadyl ions in an intact macrocyclic form. Further, the vanadyl ions present in the macrocyclic binuclear oxovanadium complex are very close to each other, and this may enhance the insulin mimetic activity by synergic effect. [source] Insulino-mimetic and anti-diabetic effects of vanadium compoundsDIABETIC MEDICINE, Issue 1 2005A. K. Srivastava Abstract Compounds of the trace element vanadium exert various insulin-like effects in in vitro and in vivo systems. These include their ability to improve glucose homeostasis and insulin resistance in animal models of Type 1 and Type 2 diabetes mellitus. In addition to animal studies, several reports have documented improvements in liver and muscle insulin sensitivity in a limited number of patients with Type 2 diabetes. These effects are, however, not as dramatic as those observed in animal experiments, probably because lower doses of vanadium were used and the duration of therapy was short in human studies as compared with animal work. The ability of these compounds to stimulate glucose uptake, glycogen and lipid synthesis in muscle, adipose and hepatic tissues and to inhibit gluconeogenesis, and the activities of the gluconeogenic enzymes: phosphoenol pyruvate carboxykinase and glucose-6-phosphatase in the liver and kidney as well as lipolysis in fat cells contributes as potential mechanisms to their anti-diabetic insulin-like effects. At the cellular level, vanadium activates several key elements of the insulin signal transduction pathway, such as the tyrosine phosphorylation of insulin receptor substrate-1, and extracellular signal-regulated kinase 1 and 2, phosphatidylinositol 3-kinase and protein kinase B activation. These pathways are believed to mediate the metabolic actions of insulin. Because protein tyrosine phosphatases (PTPases) are considered to be negative regulators of the insulin-signalling pathway, it is suggested that vanadium can enhance insulin signalling and action by virtue of its capacity to inhibit PTPase activity and increase tyrosine phosphorylation of substrate proteins. There are some concerns about the potential toxicity of available inorganic vanadium salts at higher doses and during long-term therapy. Therefore, new organo-vanadium compounds with higher potency and less toxicity need to be evaluated for their efficacy as potential treatment of human diabetes. [source] Eliminating a sulfuric acid mist plume from a wet caustic scrubber on a petroleum coke calcinerENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2001Charles A. Brown Reducing sulfuric acid mist emissions and eliminating the visible plume that remained after steam dissipation were the objectives of a project recently completed for a petroleum coke calciner. The coke calciner produces flue gas containing SO2 that is treated with a wet caustic scrubber. The scrubber is extremely efficient at removing most of the SO2, but some oxidizes to SO3, catalyzed by vanadium in the coke dust that collects in the waste heat boiler. Submicron droplets of H2SO4 form when the flue gas is quenched by the scrubber liquor, and makes its way through the scrubber. This paper describes the installation of, and performance test results for, a wet electrostatic precipitator (WESP), as well as SO2 scrubber modifications that were re q u i red to make room for the WESP. The successful project significantly reduced sulfuric acid mist emissions, eliminating the visible plume while maintaining a very low SO2 outlet concentration, even after removing one of three gas-liquid contactors. [source] Synthesis and Cytotoxicity Studies of Fluorinated Derivatives of Vanadocene YEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2009Brendan Gleeson Abstract From the reaction of 6-(2-fluoro-4-methoxyphenyl)fulvene (1a), 6-(3-fluoro-4-methoxyphenyl)fulvene (1b) and 6-[4-(trifluoromethoxy)phenyl]fulvene (1c) with LiBEt3H, lithiated cyclopentadienide intermediates (2a,c) were synthesised. These intermediates were then transmetallated to vanadium with VCl4 to yield the benzyl-substituted vanadocenes bis[(2-fluoro-4-methoxybenzyl)cyclopentadienyl]vanadium(IV) dichloride (3a), bis[(3-fluoro-4-methoxybenzyl)cyclopentadienyl]vanadium(IV) dichloride (3b), and bis[(4-trifluoromethoxybenzyl)cyclopentadienyl]vanadium(IV) dichloride (3c). The three vanadocenes 3a,c were characterised by single-crystal X-ray diffraction. All three vanadocenes had their cytotoxicity investigated through MTT-based preliminary in-vitro testing on the LLC-PK and Caki-1 cell lines in order to determine their IC50 values. Vanadocenes 3a,c were found to have IC50 values of 6.0 (+/,4), 35 (+/,7) and 13 (+/,3) ,M on the LLC-PK cell line and IC50 values of 78 (+/,11), 18 (+/,16) and 2.2 (+/,0.5) ,M on the Caki-1 cell line respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Vanadium Carbonyl Nitrosyl Compounds: The Carbonyl Nitrosyl Chemistry of an Oxophilic Early Transition MetalEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2009Hongyan Wang Abstract The vanadium carbonyl nitrosyl compounds V(NO)(CO)n (n = 5, 4, 3) and V2(NO)2(CO)n (n = 9, 8, 7) have been examined by density functional theory in order to assess the effect of the oxophilicity of vanadium on its metal carbonyl nitrosyl chemistry. The expected octahedral structure for the experimentally known, but surprisingly unstable, V(NO)(CO)5, is confirmed by DFT. The optimized structures of the unsaturated derivatives V(NO)(CO)4 and V(NO)(CO)3 can be derived from the octahedral V(NO)(CO)5 structure by loss of one or two carbonyl groups, respectively. This leads to anearly square-planar predicted structure for V(NO)(CO)3. The lowest energy structures for the binuclear derivatives V2(NO)2(CO)n (n = 9, 8, 7) have exclusively two-electron donor carbonyl groups and three-electron donor linear nitrosyl groups with metal,metal distances corresponding to the formal bond orders required for the favored 18-electron configurations. Bridging carbonyl groups appear to be preferred energetically over bridging nitrosyl groups in the V2(NO)2(CO)n structures in contrast to the similar carbonyl nitrosyl compounds of later transition metals. The saturated V2(NO)2(CO)9, with a relatively long V,V distance of 3.583 Å (B3LYP) or 3.205 Å (BP86), is thermodynamically unstable with respect to dissociation into V(NO)(CO)5 + V(NO)(CO)4.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Gas-Phase Chemistry of Vanadium Oxide Cluster Cations VmOn+ (m = 1,4; n = 1,10) with Water and Molecular OxygenEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2008Sandra Feyel Abstract Bare vanadium oxide cluster cations VmOn+ (m = 1,4; n =1,10) generated by electrospray ionization are investigated with respect to their reactivity toward water and molecular oxygen by using mass spectrometric techniques. Besides ion hydration, the ion/molecule reactions of VmOn+ with oxygen-labeled water (H218O) also lead to 16O/18O exchange reactions of the vanadium oxide clusters cations. Although the probability of degenerate 16O/18O exchange between VmOn+ and water is fairly high for the cluster cations with a medium valence state of vanadium, oxygen-atom exchange reactions between VmOn+ and 18O2 can only be accomplished by VO+, V3O6+, and V4O8+. Particularly interesting is the fact that not only oxygen atoms from vanadyl units are exchanged in the cluster cations, but bridging oxygen atoms are also most likely involved in the processes. Other reaction channels for the interaction of VmOn+ cluster cations with molecular oxygen are reported as well, such as oxidative degradation of the low-valent cluster cations upon collision with O2 and formation of association complexes for the high-valent cluster cations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] | |||||||||||||||||||||||||||||||||||||