Tungstate Complexes Research Articles

Peroxo–tungstate(VI) complexes: syntheses, characterization, reactivity, and DFT studies

Three new oxodiperoxo–tungsten(VI) complexes containing benzene core carboxylic acids, viz., benzoic acid, 2-chlorobenzoic acid, and 3-aminobenzoic acid as co-ligands have been synthesized from reaction of Na2WO6H4, 30% H2O2 and the corresponding co-ligands in aqueous medium. The compounds have been comprehensively characterized by elemental analyses, FT-IR, 1H NMR, UV–Vis spectral studies as well as by mass spectrometric and TGA analyses. The infrared spectra suggest occurrence of terminally bonded W=O as well as triangular bidentate peroxo groups (C2v) and monodentate carboxylate group bound to the WO4+ center. The mass spectra of the compounds are in good agreement with proposed molecular formulations. Thermogravimetric analyses indicate the existence of both lattice and coordinated water molecules in the complexes. Density functional theory (DFT) calculations were used to compute the frequencies of relevant vibrational modes, electronic properties and also to investigate structure of the compounds. Compound potassium(aquo)(2-chlorobenzoato)oxodiperoxo–tungstate(VI)dihydrate acts as an oxidant for bromide ion in aqueous phase bromination of chosen organic substrates to their corresponding bromo-organics.

Multinuclear 183W and 13C NMR and indirect photometry study for the identification and the characterization of new complexes of sugar acids

Colourless tungstate complexes of the sugar acids, l-manonnic, d-glucaric and galactaric acids have been studied in aqueous solutions. Multinuclear 13C and 183W NMR have been used to identify the structures of the complexes and the sites of chelation of each ligand. Indirect photometry has been used to determine the stoichiometry and the stability constants of the complexes. For mannonic acid, two complexes of the lactic type with a mono-nuclear and a di-nuclear tungsten core have been identified at acidic pH. In these complexes, a (OH) group at the carbon atom in α position is necessary to the formation of the complex and only the hydroxyl groups (OH) of the carboxyl function and of the carbon atom in α position belongs to the site of chelation. Upon increasing the pH, the lactic complexes disappear: first the mono-nuclear, then also the di-nuclear lactic complexes, however a new complex of mixed (lactic + erythro) type with a (5, 2) composition has been observed. Upon increasing the pH a single erythro complex appears and at pH 10 a small amount of threo (tetradentate) type complex has been observed. For glucaric and galactaric acids , a new tri-nuclear complex (3, 3, 6) is formed in acid medium, this complex is composed of three mono-nuclear bidentate sites of chelation related one to the other. Upon increasing the pH, these new tri-nuclear complexes disappear and only for the W-galactarate system there is formation of a di-nuclear tetradentate complex of type erythro analogous to the complex of the mannonic acid.

Indirect photometry and multinuclear 13C and 183W NMR study of tungstate complexes of sugar acids : Stabilities and structures

The tungstate complexes of the sugar acids, meso-tartaric and l-gulonic acids, have been studied in aqueous solutions. Indirect photometry has been used to determine the stability constants and the stoichiometry of these colourless complexes. Multinuclear 13C and 183W NMR spectroscopies have been used to specify the structures of the complexes and the sites of chelation of the ligand. For meso-tartaric acid, complexes of the lactic type with a mononuclear and with a dinuclear tungsten core have been identified. In these type lactic complexes, only the hydroxyl groups of the carboxyl function and the atom carbon in α position belong to the site of chelation of the tungstate complexes. Both α-hydroxyacid moieties of the meso-tartaric acid are involved in the chelation. For l-gulonic acid, lactic type complexes with a mononuclear and a dinuclear tungsten core have been observed at acidic pH. Upon increasing the pH, the lactic complexes disappear: first the mononuclear, then the dinuclear complexes. In pH range 4–8, for gulonic acid, dual lactic, threo (tetradentate) type complexes occur, the dual lactic, erythro and lactic, threo complexes exist. At pH 10, for gulonic acid, a single complex has been identified in which the ligand is pentadentate. In this complex, all carbon atoms of the ligand are involved in the site of chelation except the carboxyl atom.

Oxoperoxo molybdenum(vi) and tungsten(vi) and oxodiperoxo molybdate(vi) and tungstate(vi) complexes with 8-quinolinol: synthesis, structure and catalytic activity

A solution obtained by dissolving MoO3 in a moderate excess of H2O2 reacts with 8-quinolinol (QOH) to give [MoO(O2)(QO)2] (1), but, when the same reaction is conducted with a large excess of H2O2, an anionic complex is formed, which reacts with PPh4Cl to give the corresponding salt [MoO(O2)2(QO)][PPh4] (2·PPh4). Freshly prepared WO3 behaves the same way and, depending on the amount of H2O2 used, as above, produces either [WO(O2)(QO)2] (3) or [WO(O2)2(QO)][PPh4] (4·PPh4), respectively. Crystallographic analyses reveal the coordination geometries around the metal center in these complexes to be distorted pentagonal bipyramids. These compounds show interesting catalytic properties in the oxidation of alcohols using H2O2 as the terminal oxidant. In the case of aromatics, including benzylic and cinnamylic alcohols, the oxidation occurs selectively, affording aldehydes or ketones with reasonably high turnover numbers. Taking benzyl alcohol as a representative case, a probable mechanism of the alcohol-to-aldehyde conversion mediated by the prepared catalysts is suggested. The oxidation of aliphatic primary alcohols, under the same conditions, does not show the above selectivity: the reaction yields the corresponding aldehydes as well as carboxylic acids. The work was also extended to study the catalytic activity towards the oxidation of phenol and various sulfides and amines using the same oxidants.

Structure and Properties of Molybdate and Tungstate Complexes of Polyvinyl Alcohol

Photochemical reduction of ions of d metals (Mo and W) in the presence of polyvinyl alcohol depends on the acidity of the solutions and on the composition of the gas medium. The effect of UV radiation on the solubility of the components in the system polyvinyl alcohol-ammonium molybdate-water was studied. The mechanism of photochemical reactions and the structure of polymer-salt complexes were discussed. Mesomorphic formations similar to liquid-crystalline arise in the polymer-salt systems due to the rigidity induced in macromolecules of the water-soluble flexible-chain polymer by complex formation with inorganic polyions.

Crystallization and X-ray diffraction measurements on recombinant molbindin, MopII, from Clostridium pasteurianum.

Clostridium pasteurianum carries three genes termed mopI, II and III encoding three molbindin isoforms, one of which has been cloned, the gene product expressed in high yield and crystallized using the hanging-drop vapour-diffusion method. Well ordered monoclinic crystals in two different crystal forms, both with space group C2, were obtained in the presence and absence of Na(2)MoO(4) and Na(2)WO(4). Ligand-bound MopII crystallized with polyethylene glycol (PEG) 400 as a precipitant, whereas apo MopII required PEG 6000. High-resolution diffraction data were collected for ligand-bound MopII structures using synchrotron radiation to 1.8 and 1.6 A resolution for the molybdate and tungstate complexes, respectively. Data were collected on apoMopII crystals to a resolution of 1.8 A in-house.

Extended X-ray absorption fine structure studies of the anion complexes of FeZn uteroferrin.

Molybdate and tungstate are strong inhibitors of the purple acid phosphatases. The binding modes of these anions to the FeZn derivative of uteroferrin, the purple acid phosphatase from porcine uterus (FeZnUf), have been characterized by X-ray absorption spectroscopy at both the iron and zinc K-edges. Pre-edge data show that both FeZnUf.MoO4 and FeZnUf.WO4 have six-coordinate iron sites. Analysis of the EXAFS regions shows that the iron sites of both molybdate and tungstate complexes are best simulated by a shell of three O or N atoms at 2.08-2.09 A and a shell of two O or N atoms at 1.93-1.95 A. On the other hand, the zinc sites have shells of five O or N atoms at approximately 2.1 A and one O or N atom at approximately 2.5 A. Because of the higher resolution of the FeZnUf. MoO4 data, the main shell at approximately 2.1 A can be further split into shells of four O or N at 2.04 A and one O or N at 2.22 A, the latter being associated with a molybdate oxygen. Outer-sphere EXAFS analysis indicates an Fe-Zn separation of approximately 3.4 A for both FeZnUf.MoO4 and FeZnUf.WO4, Fe-Mo/W distances of 3.2 A, and Zn-Mo/W distances of 3.6-3.7 A. Thus, molybdate and tungstate bridge the FeZn active site like phosphate, but do so unsymmetrically. The asymmetric bidentate bridging mode of molybdate and tungstate helps explain the effect of these anions on the redox properties of the diiron uteroferrin.

Furanose vs. acyclic forms of carbohydrate ligands. A multinuclear NMR spectroscopy study of the molybdate and tungstate complexes of d- glycero- l- manno-heptose

The formation of dinuclear tungstate and molybdate complexes of d- glycero- l- manno-heptose was studied in aqueous solution by 13C and 183W NMR spectroscopy. The chelating aldose is always tetradentate and occurs exclusively in furanose or acyclic hydrated forms, the proportions of which depend on the pH and nature of the metal ion. In the tungstate species, two types of major complexes, noted M (O-2,3,5,6) and L (O-1,2,3,5) according to the site of chelation, involve the ligand in furanose form. In one of the minor tungstate complexes, chelation occurs at the galacto (O-3,4,5,6) site of the acyclic heptose. In the molybdate species, the complex of type M does not exist, and besides the complex of type L, the major species involve the acyclic ligand with either the galacto (O-3,4,5,6) or arabino (O-1,2,3,4) sites of chelation. Multinuclear NMR data are provided for the identification of the various types of complexes. Marked differences were noticed with respect to the complexes of d-mannose, in which species of type L prevailed with both molybdate and tungstate.

A 13C and 183W NMR study of [formula omitted] acid as a multisite ligand in tungstate complexes

The formation of complexes ( x, y, z) between x tungstate ions, y d-glycero- d-gulo- heptonate ions, and z protons was studied in aqueous solution by 13C and 183W NMR spectroscopy. The overall equilibrium constant for the complex-forming reaction was obtained by a competition method, showing that a (2,2,2) species prevails at pH 4–5. Depending on the pH, various species are formed that involve chelating oxygen atoms originating from hydroxyl groups only, or from the carboxyl and the α-hydroxyl groups. In acidic medium, three types of complexes are formed: a (2,1,2) complex at the arabino site (O-4,5,6,7), two complexes at the O-1,2 site which have either (1,2,2) or (2,2,2) compositions, and a mixed 5:2 complex involving O-1,2,4,5,6,7 of each ligand. In alkaline medium, the carboxylate group is not involved in chelation and a single (2,1,1) complex of the pentadentate ligand (O-2,3,4,5,6) was characterized.

Tungstate complexes of aldoses and ketoses of the lyxo series. Multinuclear NMR evidence for chelation by one or two oxygen atoms borne by the side chain of the furanose ring

The formation of tungstate complexes of aldoses and ketoses with lyxo configuration was studied in aqueous solution by 13C and 183W NMR spectroscopy. Two series of complexes were structurally characterized, in which the sugars adopt the furanose form and chelate a ditungstate group at a tetradentate site. All sugars form a major complex (type L for lyxo) similar to the molybdate species, in which the sites of chelation, O-1,2,3,5 for aldoses or O-2,3,4,6 for ketoses, involve the anomeric oxygen atom and the side chain atom O-5 or O-6. A second type of complex was identified (type M for manno), in which the sites of chelation are O-2,3,5,6 for d-mannose (tungstate species only) and O-3,4,6,7 for d- manno-heptulose (tungstate and molybdate complexes). The overall equilibrium constants for the formation of the complexes are reported and show that ketoses form stronger complexes than aldoses.

Structures and Stabilities of Tungstate Complexes of .alpha.-Hydroxy Acids. 183W NMR Study of the Influence of Ligand Substitution

Structures and Stabilities of Tungstate Complexes of .alpha.-Hydroxy Acids. 183W NMR Study of the Influence of Ligand Substitution

183W NMR Studies of Tungstate Complexes of Carbohydrates. 3. Species Formed with All-threo Alditols Acting as Tridentate, Tetradentate, or Pentadentate Ligands

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT183W NMR Studies of Tungstate Complexes of Carbohydrates. 3. Species Formed with All-threo Alditols Acting as Tridentate, Tetradentate, or Pentadentate LigandsStella Chapelle, Jean-Paul Sauvage, P. Koell, and Jean-Francois VerchereCite this: Inorg. Chem. 1995, 34, 4, 918–923Publication Date (Print):February 1, 1995Publication History Published online1 May 2002Published inissue 1 February 1995https://doi.org/10.1021/ic00108a024RIGHTS & PERMISSIONSArticle Views127Altmetric-Citations17LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (654 KB) Get e-Alerts Get e-Alerts

183W NMR Studies of Tungstate Complexes of Carbohydrates. 2.Competitive Formation of erythro and threo Complexes of Alditols. Characterization of a Novel Bis-Dinuclear Complex Formed with Perseitol

Tungstate complexes of alditols have been studied in aqueous solution by 183 W and 13 C NMR spectroscopies. The ligands used in this work may chelate a ditungestate group though several different sites having erythro of threo configurations and therefore yield mixtures of complexes. The structural type of each complex was defined by the characteristic pattern of its 183 W NMR spectrum, and the sites of chelation were identified by 13 C NMR spectroscopy Alditols which possess an asymmetrical site of erythro configuration (D-arabinitol, D-mannitol, D-glucitol) form two isomeric complexes, as this tetradentate site can be occupied in two reversed orientations

Screening of Metal Complexes for Biological Activity. Part-III. Copper(II) and Nickel(II) Tungstate Complexes with Ethylenediamine and Propylenediamine

Screening of Metal Complexes for Biological Activity. Part-III. Copper(II) and Nickel(II) Tungstate Complexes with Ethylenediamine and Propylenediamine

Isolation and crystal structure of two novel oxo-persulphido amidrazone tungstate complexes, WO(S 2) 2{RC(NH)NHNH} (R = CH 3, CH 3CH 2)

A new method for preparing amidrazone is described. The amidrazone oxo-persulphido complexes were obtained from the new reaction system of WS 4 2−/P 2S 5/H 2NNH 2·2HCl with CH 3CN or CH 3CH 2CN in air at ambient temperature. In the two complexes WO(S 2) 2{CH 3C(NH)NHNH} ( I) and WO(S 2) 2{CH 3CH 2C(NH)NHNH} ( II), the coordination polyhedron of tungsten is pentagonal bipyramidal, where the two axial ligands are the terminal oxo atom and the N(H) coordinating atom of NHNH in amidrazone. The spectroscopic properties of the complexes are also reported.

1H NMR and NOE studies of the purple acid phosphatases from porcine uterus and bovine spleen.

The diiron active sites of the purple acid phosphatases from porcine uterus (also called uteroferrin, Uf) and bovine spleen (BSPAP) and their complexes with tungstate are compared by 1H NMR and NOE techniques. The paramagnetically shifted features of the 1H NMR spectrum of reduced BSPAP are similar to those of reduced Uf, while the spectra of the tungstate complexes are almost identical. These observations suggest that the two active sites are quite similar, in agreement with the greater than 90% sequence homology found in the two enzymes. Nuclear Overhauser effect (NOE) experiments on the His N-H resonances show that the Fe(III)-His residue is N epsilon-coordinated, while the Fe(II)-His is H delta-coordinated in both enzymes. On the basis of the above NMR and NOE results, our previously proposed model for the dinuclear iron active site of Uf [Scarrow, R. C., Pyrz, J. W., & Que, L., Jr. (1990) J. Am. Chem. Soc. 112, 657-665] is corroborated, refined, and found to represent the diiron center of BSPAP as well.

Tungsten-183 NMR studies of tungstate complexes of carbohydrates. 1. Characterization of two structural types in the alditol series. Evidence that the tungstate and molybdate threo complexes are not homologous

Dinuclear tungstate complexes of alditols have been studied in aqueous solution by 13 C and 183 W NMR spectroscopies. Ligands possessing hydroxyl groups in erythro configuration (erythritol, galactitol) formed a series of tetradentate complexes homologous to the known corresponding molybdate erytro compounds. In contrast, ligands with threo hydroxyl groups (threitol, xylitol) form tridentate complexes different from the tetradentate molybdate threo species

Synthesis, characterisation and thermal behaviour of cyano(oxine)-molybdenum(IV) and -tungsten(IV)

A new class of adduct compounds of octacyano-molybdate(IV) and -tungstate(IV) complexes with oxine, of the type K 4[M(CN) 8]·8(C 9H 70N)·5H 20 (where M = Mo or W) was synthesised. FTIR spectra show bands in the range 2000–2200 cm −1 and around 1120 cm −1 indicating the presence of the cyano group, -CN, as well as oxine through the -N=0 mode. The d spacing from the X-ray diffraction patterns were determined and compared with those of known compounds. Thermogravimetric analysis indicated the removal of uncoordinated water up to 150°C. Oxine and cyano molecules were removed stage by stage at higher temperatures. The final products from thermal treatment are oxides of polymeric nature. The kinetic parameters n and E a were determined by means of TGA and DTG thermograms.

Study of dehydration kinetics of heteropoly molybdate and tungstate complexes of gallium(III)

The dehydration processes of heteropoly hexamolybdate and dodecatungstate complexes of gallium were investigated. The kinetics of dehydration were studied in a flow reactor, the obtained activation energy values being 50–107 kJ/mol, and the pre-exponential factor 104−1013s−1. The nature of the external cation does not influence the dehydration kinetics essentially. The activation energy and pre-exponential factor values increase on transition from the high-hydrated tungstates to the low-hydrated molybdates.

Emulsion membrane extraction of Am(III) and Am(IV) in systems with tertiary and secondary amines

The stability of emulsions, containing tri-n-octylamine and di-n-octylamine salts in the organic phase and nitric acid in the aqueous phase has been studied. Optimal conditions for the extraction of Am(III) and Am(IV) phosphorus tungstate complexes with such emulsions have been determined. Emulsion membrane extraction is shown to be more effective for this purpose than conventional liquid extraction.