0000000000213442
AUTHOR
Antonio Cervilla
showing 20 related works from this author
Compounds of molybdenum(VI) with aspartic acid: A spectrophotometric and potentiometric study of the formation and interconversion equilibria in aque…
1990
Addition of Na2MoO4 to an excess of aspartic acid (AspH2) can produce any of four different complexes depending on the pH, namely [MoO3(Asp)]2−, [Mo2O5(Asp)2]2−, [Mo2O4(OH)(Asp)2]− and [Mo2O4(Asp)2]. The ranges of formation of these species with pH, the number of equivalents of acid necessary for their formation, and their stoichiometries, condensation degrees and stability constants, have been calculated by potentiometric and spectrophotometric techniques. The aspartic acid acts as a tridentate ligand in all cases.
Molybdenum(VI)-dioxo complexes with sterically bulky thiocarboxylate ligands. Reactions with aliphatic thiols and electrochemical properties
1991
Abstract Under acid conditions, the reaction of (Bu n 4 N)2[Mo VI O 2 (O 2 CC(S)Ph 2 ) 2 ] with aliphatic thiols yields the monomeric [Mo V O(O 2 CC(S)Ph 2 ) 2 ] − as unique complex product. The experimental pseudo-first order rate constant with respect to the Mo(VI) complex was found to be K =6.1 × 10 −5 s −1 . At neutral pH, however, an unstable Mo(IV) species was formed which was also electrochemically detected in a reversible Mo(V,IV) couple. [Mo V O(O 2 CC(S)Ph 2 ) 2 ] − appears to be obtained by the reaction of [Mo IV O(O 2 CC(S)Ph 2 ) 2 ] 2− with unreacted [Mo VI O 2 (O 2 CC(S)Ph 2 ) 2 ] 2− . Steric features on the ligand (gemdiphenyl groups) explain that the latter reaction does not…
Improving epoxide production using Ti-UVM-7 porous nanosized catalysts
2002
Nanosized Ti-UVM-7 materials with a hierarchical system of pores at two different length scales have been prepared through a one-pot procedure by using a simple template agent; the catalytic activity and selectivity of the resulting materials in bulky olefin epoxidation by organic peroxides are the highest reported to date.
Voltammetric behaviour of monomeric fac-trioxomolybdenum(VI) complexes with aminocarboxylic ligands in aqueous media
1992
Abstract Cyclic voltammetry, polarography and controlled-potential coulometry experiments have been used to characterize the electrochemical reduction of fac-MoO3L2− complexes (L = aspartic acid or iminodiacetic acid) in aqueous media. These complexes are reduced in two irreversible proton-assisted steps to give an oxo-bridged molybdenum(V) species and then to a molybdenum(III) dimer species. At pH 4.5, the former reduction step for the iminodiacetic acid ligand occurs at Ep = −0.75 V, while the second one appears at −1.12 V vs SCE. The overall electrochemical process can be described in terms of a homogeneous chemical reaction, coupled between two electron transfers (ECE mechanism), that i…
The reduction of tris-dithiolene complexes of molybdenum(vi) and tungsten(vi) by hydroxide ion: kinetics and mechanism
2004
The kinetic study of the spontaneous reduction of some neutral tris-dithiolene complexes [ML3] of molybdenum(VI) and tungsten(VI), (L = S2C6H42−, S2C6H3CH32− and S2C2(CH3)22−; M = Mo or W) by tetrabutylammonium hydroxide in tetrahydrofuran-water solutions demonstrates that OH− is an effective reductant. Their reduction is fast, clean and quantitative. Depending upon both the molar ratio in which the reagents are mixed and the amount of water present, one- or two-electron reductions of these tris-dithiolene complexes were observed. If Bu4NOH is present in low concentration or/and at high concentrations of water, the total transformation of the neutral M(VI) complex into the monoanionic M(V) …
NMR studies on [Rh(η6-arene)(P(OPH)3)2]ClO4 in the presence of acetone-d6. Arene dissociation and dynamic behaviour of the solvent complex
1985
Abstract Dissociation of the complexes [Rh(η 6 -arene)L 2 ]ClO 4 (arene = mesitylene (Ia), toluene (Ib) and benzene (Ic); L = P(OPh) 3 ) with loss of the arene ligand in CD 2 Cl 2 / acetone- d 6 (95/5 mol/mol) has been studied by 31 P NMR spectroscopy; for initial 0.025 M concentrations of degrees of dissociation were 0.23, 0.33 and 0.85, respectively. The dissociations were first-order, with half-lifes of 31 (Ia), 1.2 (Ib) and 0.7 (Ic) h. The solvent complex [Rh(acetone) m L 2 ]ClO 4 produced by these dissociation reactions showed unusual dynamic structural behaviour. In dry acetone the two phosphorus nuclei were magnetically equivalent (species II-A 2 ), whereas in acetone solutions conta…
The catalytic reduction of nitrobenzene at the [MoVIO2(O2CC(S)(C6H5)2)2]2? complex intercalated in a Zn(II)-Al(III) layered double hydroxide host: A …
2001
The heterogeneous reduction of nitrobenzene by thiophenol catalyzed by the dianionic bis(2-sulfanyl-2,2-diphenylethanoxycarbonyl) dioxomolybdate(VI) complex, [MoVIO2(O2CC(S)(C6H5)2)2]2−, intercalated into a Zn(II)–Al(III) layered double hydroxide host [Zn3−xAlx(OH)6]x+, has been investigated under anaerobic conditions. Aniline was found to be the only product formed through a reaction consuming six moles of thiophenol for each mol of aniline produced. The kinetics of the system have been analyzed in detail. In excess of thiophenol, all reactions follow first-order kinetics (ln([PhNO2]/[PhNO2]0) = −kappt) with the apparent rate constant kapp being a complex function of both initial nitrobenz…
Reduction of tris(benzene-1,2-dithiolate)molybdenum(VI) by hydroxide ions in dry tetrahydrofuran solution.
2001
Tris(benzene-1,2-dithiolate)molybdenum(VI) reacts rapidly and quantitatively with tetrabutylammonium hydroxide to yield the corresponding Mo(V) and Mo(IV) complexes and hydrogen peroxide; the reaction has been executed in dry tetrahydrofuran where the reaction rate shows a fair dependence on complex and OH2 concentrations. Cervilla Avalos, Antonio, Antonio.Cervilla@uv.es ; Perez Pla, Francisco, Francisco.Perez@uv.es ; Llopis Jover, Elisa, Elisa.Llopis@uv.es
Reactivity of Neutral Mo(S2C6H4)3 in Aqueous Media: an Alternative Functional Model of Sulfite Oxidase.
2009
The kinetics of the reaction of neutral [Mo(S2C6H4)3] with hydrogen sulfite to produce the anionic Mo(V) complex, [Mo(S2C6H4)3]-, and sulfate have been investigated. It has been shown that [Mo(S2C6H4)3] acts as the electron-proton sink in the oxygenation reaction of HSO3(-) by water. Reaction rates, monitored by UV/vis stopped-flow spectrometry, were studied in THF/water media as a function of the concentration of HSO3(-) and molybdenum complex, pH, ionic strength, and temperature. The reaction exhibits pH-dependent HSO3(-) saturation kinetics, and it is first-order in complex concentration. The kinetic data and MS-ESI spectra are consistent with the formation of [Mo O(S2C6H4)2(S2C6H5)]- (1…
Compounds of tungsten(VI) with citric acid: A spectrophotometric, polarimetric and hydrogen-1, carbon-13 N.M.R. study of the formation and interconve…
1986
Tungsten(VI)-citrate complexes, which occur in aqueous solution, were studied by polarimetric and absorbance measurements. The pH of the medium is the principal variable controlling complex formation and interconversion equilibria. At high pH (>6), the stable complexes are monomers with 1∶2 and 1∶1 stoichiometry, depending on the tungsten(VI)-citrate ratio, while at lower pH two different dinuclear complexes are formed. The intervals of existence of these species with the pH, the number of equivalents of acid necessary for their formation, as well as the conditional stability constant, have also been calculated. The structure of these compounds have been investigated by1H and13C-n.m.r. spec…
Electrochemistry of hydrotalcite-supported bis(2-mercapto-2,2-diphenyl-ethanoate) dioxomolybdate complexes.
1998
The redox properties of the hydrotalcite-intercalated bis(2-mercapto-2,2-diphenyl-ethanoate) dioxomolybdate(VI) complex are investigated by cyclic voltammetry by using modified carbon paste electrodes and clay-modified electrodes. The electrochemical data provide evidence that boundary-associated species involving the VI, V and IV oxidation states of molybdenum are responsible for the electroactivity.
Dalton communication. Crystal structure and oxo-transfer properties of [NH4]2[WVIO2{O2CC(S)Ph2}2]
1994
The complex [NH4]2[WVIO2{O2CC(S)Ph2}2] is the first example of a non-dithiolene tungsten complex capable of oxidising benzoin to benzil in methanol; the reduced complex product formed, presumably a monomeric WVIO species, was reoxidised with nitrate ions, regenerating the starting WVIO2 complex which then acts as a true homogeneous catalyst.
Electrochemical reduction of the nitrite to ammonium ions in presence of [MoO2(O2CC(S)C6H5)2]2−
1995
Abstract Ammonia is formed during potentiostatic reduction of sodium nitrite solutions on the nafion-complex-coated electrode. When (NH4)2[MoO2(O2CC(S)(C6H5)2)2] is present in NaNO2 solutions a polarographic wave is associated to electrocatalytic reduction of nitrite ion. The wave height varies linearly on the concentration of nitrite ion, allowing a procedure for analysing this ion. This electrochemical behaviour distinguishes the nitrite from the nitrate ions. The Mo(VI), Mo(V), and Mo(IV) are involved in catalytic redox processes determining formation of NH4+ from nitrite ions.
Lactate complexes of molybdenum(VI)
1983
Spectrophotometric and cryoscopic studies of the molybdenum(VI)-lactic acid (C3O3H6) system show the existence of three different oxoanion complexes in aqueous solution which have been isolated as [Co(en)3]3+ salts. These are one molybdodilactate {[MoO2(C3O3H42]2−} and two dinuclear 1/1 species: [Mo2O5(C3O3H4)2(H2O)2]2− and [Mo2O3(OH)3-(C3O3H4)2]−. The pH of the medium is the main variable, controlling the formation equilibria which are similar to those previously described for other α-hydroxy-acid ligands.
A kinetic model for the oxidation of benzenethiol catalyzed by the [MoVIO2(O2CC(S)(C6H5)2)2]2− complex intercalated in a Zn(II)–Al(III) layered doubl…
2009
Abstract The heterogeneous oxidation of benzenethiol catalyzed by the dianionic bis(2-sulfanyl-2,2-diphenylethanoxycarbonyl) dioxomolybdate (VI) complex intercalated into a Zn(II)–Al(III) layered double hydroxide (LDH) host have been investigated under aerobic conditions. The kinetics of the system has been analysed in detail. In ethanol, the benzenethiol is cleanly oxidized to diphenyl disulfide in the acidic media provided by the protonic resin Amberlite IR-120(H). The reaction is second-order in benzenethiol, and the apparent rate coefficient has been found to be proportional to the catalyst weight and inversely proportional to the initial concentration of the substrate. A catalytic cycl…
Mononuclear mixed oxosulfidomolybdate(VI) complexes with aminodicarboxylic ligands. Synthesis and spectroscopic characterization by multinulcear magn…
1993
Addition of B2S3 to a methanolic solution of the MoVIO3L2− complex (L=N,N-bis(ethanoic acid)-1-amino-2- methylthio-ethane) results in the formation of two different monomeric oxosulfidomolybdate(VI) complexes, [MoO2SL]2− and [MoOS2L]2− as indicated by 1H, 13C, 17O and 95Mo NMR spectroscopy and by the reaction of these two sulfurated species with triphenylphosphine. The temperature dependences of the 1H NMR spectra indicate exchange processes for both sulfido complexes. Their redox properties are discussed and contrasted with those observed for the parent fac-trioxo molybdenum(VI) complex. The primary synthetic route to mixed oxosulfido [MoO3−nSnL]2− complexes described here can be extended …
Complexes of Tungsten(VI) with Mucic Acid: a Spectrophotometric and Polarimetric Study in Aqueous Solution
1986
Abstract Spectrophotometric work on mucic acid-W(VI) system shows the formation of three different oxoanion complexes in aqueous solution; their stability is dependent upon pH. One of the complexes is monomeric tungstodimucate and the other two are 2/2 species. An anomalous cryoscopic behaviour, similar to that of W(VI) tartaric system, has been observed for the dimeric complex formed at higher pH. The stoichiometries and conditional dissociation constants have been polarimetrically determined by means of competitive reactions between the mucic and tartaric ligands. 1 H and 13 C NMR spectra have been interpreted for the similar complex species of both mucic and tartaric acids.
Tungsten-mannitol and sorbitol complexes: Structural characterization by IR and carbon-13 nuclear magnetic resonance spectroscopy
1986
Abstract Polarimetric and spectrophotometric studies of the mannitol-tungsten(IV) system show the formation of three table complexes. Their stoichiometries, degrees of condensation and interconversion equilibria have been studied. The structure of these compounds has been investigated by 13C NMR spectroscopy in aqueous solution and by IR spectroscopy in the solid state for the two species stable at pH
Complexes of molybdenum(VI) with organic diacid ligands: The molybdenum(VI)-malonic acid system
1983
Malonic acid (C3O4H4) and MoVI form in aqueous solution two dinuclear dioxo-complexes of which the stability is a function of the pH of the medium. Both complexes have a 1∶1 metal-ligand stoichiometric ratio, and the interconversion may involve a structural rearrangement. Conditional dissociation constants have been determined spectrophotometrically. Saline cryoscopy supports the spectrophotometric results. Salts of [Co(en)3]3+ have been isolated. The ligand behaviour of malonic acid differs partially from that observed for α-polyhydroxy ligands.
Tungsten(VI)-gluconic acid complexes: Polarimetric and13C-N.m.r. Studies in an excess of tungsten(VI)
1986
A polarimetric study of the tungsten (VI)-gluconic acid system in an excess of metal reveals the formation of four stable complexes: two monomers with 1 : 2 and 2: 1 stoichiometries and two dimers of 2:2 composition. The pH ranges of these species, the amount of acid equivalents their formation requires, and their conditional stability constants have also been calculated.