Synthesis and characterization of molybdenum oxo complexes of two tripodal ligands: reactivity studies of a functional model for molybdenum oxotransferases

Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (L-OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L-O)]PF6. Similarly, the reaction of N-(2-mercaptobenzyl)-N,N-bis(2-pyridylmethyl)amine (L-SH) with MoO2(acac)2 leads to the formation of [MoO2(L-S)]+. The dioxo-molybdenum complex [MoO2(L-O)]+ reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV)O(L-O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L-O)]PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [(L-O)OMo(micro-O)MoO(L-O)](PF6)2. The crystal structures of [MoO2(L-O)]PF6 and the micro-oxo bridged dimer are presented.     

Oxomolybdenum(VI) and (V) complexes with 6–methyl-4–hydroxypyrimidinyl hydrazones

Dioxomolybdenum(VI) complexes [MoO2(L)H2O] and oxomolybdenum(V) complexes [Mo2O3(LH)2Cl2] (where LH2=hydrazones derived from 6–methyl-4–hydroxy-2–hydrazinopyrimidine with salicylaldehyde, 5–methyl-, 5–chloro-, 5–bromo-, 3–methoxy-salilcylaldehyde, or 2–hydroxy-1–naphthaldehyde) have been prepared and characterised by spectroscopic and physico-chemical methods. The MoVI complexes are diamagnetic octahedral structures, whilst the MoV complexes are paramagnetic and probably dimeric, via oxobridging.     

Electronic structure of neutral and monoanionic tris(benzene-1,2-dithiolato)metal complexes of molybdenum and tungsten

The reaction of 3 equiv of the ligand 2-mercapto-3,5-di-tert-butylaniline, H2[LN,S], or 3,5-di-tert-butyl-1,2-benzenedithiol, H2[LS,S], with 1 equiv of [MoO2(acac)2] or WCl6 (acac=acetonylacetate(1-)) in methanol or CCl4 afforded the diamagnetic neutral complexes [MoV(LN,S)2(L*N,S)]0 (1), [MoV(LS,S)2(L*S,S)] (2), and [WV(LS,S)2(L*S,S)] (3), where (L*N,S)- and (L*S,S)- represent monoanionic pi-radical ligands (Srad=1/2), which are the one-electron oxidized forms of the corresponding closed-shell dianions (LN,S)2- and (LS,S)2-. Complexes 1-3 are trigonal-prismatic members of the electron-transfer series [ML3]z (z=0, 1-, 2-). Reaction of 2 and 3 with [N(n-Bu)4](SH) in CH2Cl2 under anaerobic conditions afforded paramagnetic crystalline [N(n-Bu)4][MoV(LS,S)3] (4) and [N(n-Bu)4][WV(LS,S)3] (5). Complexes 1-5 have been characterized by X-ray crystallography. S K-edge X-ray absorption and infrared spectroscopy prove that a pi-radical ligand (L*S,S)- is present in neutral 2 and 3, whereas the monoanions [MV(LS,S)3]- contain only closed-shell dianionic ligands. These neutral species have previously been incorrectly described as [MVI(L)3]0 complexes with a MoVI or WVI (d0) central metal ion; they are, in fact MV (d1) (M=Mo, W) species: [MoV(LS,S)2(L*S,S)] and [WV(LS,S)2(L*S,S)] with a diamagnetic ground state St=0, which is generated by intramolecular, antiferromagnetic coupling between the MV (d1) central ion (SM=1/2) and a ligand pi radical (L*S,S)- (Srad=1/2).     

铅醇盐配合物的电化学合成

铅醇盐配合物的电化学合成;电化学; 牺牲阳极;铅醇盐     

Substoichiometric Extraction of Mercury by Diethyldithiocarbamic Acid

The substoichiometric extraction of Hg²⁺ using diethyldithiocarbamic acid and ²⁰³Hg tracer was studied. Chloroform was employed to remove the complexes from the aqueous media which were 0.5M H₂SO₄ or 1 M HClO₄ and 0 to 5 M NaCL. - Systems containing Cl^? allowed extraction of Hg²⁺ for all DDC/Hg molar ratios, the extracted complexes being HgCl(DDC) and Hg(DDC)₂. Their exchange constant was determined. - In the absence of Cl^?, no extraction could be effected in either system if the DDC/Hg molar ratio was < 1; the H₂SO₄ system remained clear, whereas a precipitate of HgClO₄(DDC) formed in the HClO₄ system. For molar ratios > 1, the extraction of Hg²⁺ increased linearly with the addition of DDC, the extracted complex being Hg(DDC)₂.     

Cation behavior at an artificial cell interface: binding distinguished by ion hydration energetics and size

The unique molybdenum oxide-based nucleophilic porous capsule/artificial cell [{(MoVI)MoVI5O21(H2O)6}12{MoV2O4(SO4)30}]72-, according to an X-ray crystallographic study, traps [Al(H2O)6]3+ complexes above the pores while interacting with the latter via hydrogen bonds; this is supported by 27Al NMR studies of the interaction of the capsule with hydrated Al3+ cations in aqueous solution.     

Extraction of Heavy Metals from Solid Material by Supercritical CO2

Extraction of heavy metal ions from solid matrix by means of an incorporation of chelating agents with supercritical carbon dioxide(scCO2) was investigated experimentally. Four commercially available chelating agents, diethylammonium diethyldithiocarbamate(Et2NH2DDC), trifluoroacetylacetone(TFA), hexafluoroacetylacetone(HFA) and thenoyltrifluoroacetone(TTA) were tested. The extraction experiments were conducted at 50 °C and 1.39×107― 2.80×107 Pa. According to the experimental results, for the extraction of Cu2+, all the chelating agents investigated here are effective. For other metal ions, such as Pb2+, Ni2+ and Cd2+, Et2NH2DDC exhibited a better extraction result, while other chelating agents were less effective. This investigation is expected to provide a tentative evaluation on the scCO2-based metal extraction from solid media.     

Resorcarene-based receptor: versatile behavior in its interaction with heavy and soft metal cations

Standard solution Gibbs energies, DeltasG degrees, of the resorcarene-based receptor 5,11,17,23-ethylthiomethylated calix[4]resorcarene, (characterized by 1H NMR and X-ray diffraction studies) in its monomeric state (established through partition experiments) in various solvents are for the first time reported in the area of resorcarene chemistry. Transfer Gibbs energies of from hexane (reference solvent) to other medium are calculated. Agreement between DeltatG degrees (referred to the pure solvents) and standard partition Gibbs energies, DeltapG degrees (solvent mutually saturated) is found. Cation-ligand interactions were investigated through 1H NMR (CD3CN and CD3OD) and conductometric titrations in acetonitrile and methanol. 1H NMR data revealed the sites of interaction of with the metal cation. The composition of the metal-ion complexes (Ag+ and Pb2+ in acetonitrile and Ag+ and Cu2+ in methanol) was established through conductometric titrations. Thus, complexes of 1:1 stoichiometry were formed between and Ag+ and Pb2+ in acetonitrile and Cu2+ in methanol. However, in moving from acetonitrile to methanol, the composition of the silver complex was altered. Thus, two metal cations are hosted by a unit of the ligand. As far as Cu2+ and in acetonitrile is concerned, conductance data suggest that metalates are formed in which up to four units of Cu2+ are taken up per unit of resorcarene. The contrasting behavior of with Cu2+ in acetonitrile relative to methanol is discussed. As far as mercury (II) is concerned, the unusual jump in conductance observed in the titration of Hg2+ with in acetonitrile and methanol after the formation of a multicharged complex (undefined composition) is attributed to the presence of highly charged smaller units (higher mobility) resulting from the departure of pendant arms from the resorcarene backbone. Isolation of these species followed by X-ray diffraction studies corroborated this statement. The thermodynamic characterization of metal-ion complexes of Ag+ and Pb2+ in acetonitrile and Cu2+ and Ag+ in methanol is reported. Final conclusions are given.     

Octadecyl silica membrane disks modified with a new Schiff's base for the preconcentration of lead and copper before their determination in water samples

A simple and fast method for the extraction and determination of ppt level of Pb2+ and Cu2+ ions using octadecyl-bonded silica membrane disks modified by a new tetradentates Schiffs base [Bis(2,4-dimethoxy benzaldehyde) ethylen diimine](TDSB) and inductively coupled plasma atomic emission spectrometry is described. Extraction efficiency, and influence of flow rate, pH, type and the least amount of acid for stripping of Cu2+ and Pb2+ from the modified disks and break through volume were evaluated. The maximum capacity of the membrane disks modified by 5 mg of TDSB used was found to be 347 +/- 7 and 470 +/- 6 microg of copper and lead, respectively. The concentration factor is 500 (for 2500 mL water sample and flow rate of 20 mL min(-1)) and detection limit of the proposed method is 12.5 and 150.5 pg/ml for Cu2+ and Pb2+, respectively. The method was applied to the determination of Cu2+ and Pb2+ ions from various water, wastewater, black tea, and hot pepper samples.     

New chloro,mu-oxo,and alkyl derivatives of dioxomolybdenum(VI) and -tungsten(VI) complexes chelated with N(2)O tridentate ligands: synthesis and catalytic activities toward olefin epoxidation

A new series of cis-dioxomolybdenum(VI) complexes MoO(2)(L(n))Cl (n = 1-5) were prepared by the reaction of MoO(2)Cl(2)(DME) (DME = 1,2-dimethoxyethane) with 2-N-(2-pyridylmethyl)aminophenol (HL(1)) or its N-alkyl derivatives (HL(n)) (n = 2-5) in the presence of triethylamine. The new mu-oxo dimolybdenum compounds [MoO(2)(L(n))](2)O (n = 1, 4, 5, 7) were also prepared by treating the corresponding ligand HL(n) with MoO(2)(acac)(2) (acac = acetylacetonate) in warm methanolic solutions or (NH(4))(6)[Mo(7)O(24)].4H(2)O in the presence of dilute HCl. Treatment of MoO(2)(L(1))Cl or [MoO(2)(L(1))](2)O with the Grignard reagent Me(3)SiCH(2)MgCl gave the alkyl compound MoO(2)(L(1))(CH(2)SiMe(3)), which represents the first example of dioxomolybdenum(VI) alkyl complex supported by a N(2)O-type ancillary ligand. The analogous chloro and mu-oxo tungsten derivatives WO(2)(L(n))Cl (n = 6, 7) and [WO(2)(L(n))](2)O (n = 1, 4, 6, 7) were prepared by the reaction of WO(2)Cl(2)(DME) with HL(n) in the presence of triethylamine. Similar to their molybdenum analogues, the tungsten alkyl complexes WO(2)(L(n))(R) (n = 6, 7; R = Me, Et, CH(2)SiMe(3), C(6)H(4)(t)Bu-4) were synthesized by treating WO(2)(L(n))Cl or [WO(2)(L(n))](2)O (n = 6, 7) with the appropriate Grignard reagents. The catalytic properties of selected dioxo-Mo(VI) and -W(VI) chloro and mu-oxo complexes toward epoxidation of styrene by tert-butyl hydroperoxide (TBHP) were also investigated.     

Polymer supported vanadium and molybdenum complexes as potential catalysts for the oxidation and oxidative bromination of organic substrates

The Schiff base (H2fsal-ohyba) derived from 3-formylsalicylic acid and o-hydroxybenzylamine has been covalently bonded to chloromethylated polystyrene cross-linked with 5% divinylbenzene (abbreviated as PS-H(2)fsal-ohyba, I). Treatment of [VO(acac)2] with PS-H2fsal-ohyba in dimethylformamide (DMF) gave the oxovanadium(iv) complex PS-[VO(fsal-ohyba).DMF] (1). Complex 1 can be oxidized into the dioxovanadium(v) species, PS-K[VO2(fsal-ohyba)] (2) on aerial oxidation in the presence of KOH or into the oxoperoxo species, PS-K[VO(O2)(fsal-ohyba)] (3) in the presence of H2O2 and KOH in DMF suspension. Similarly, PS-[MoO(2)(fsal-ohyba).DMF] (4) has been isolated by the reaction of [MoO2(acac)2] with PS-H2fsal-ohyba. All these complexes have been characterised by various techniques. These complexes catalyse the oxidation of styrene, ethylbenzene and phenol efficiently. Styrene gives five reaction products namely styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde, while ethylbenzene gives benzaldehyde, phenyl acetic acid, styrene and 1-phenylethane-1,2-diol. The oxidation products of phenol are catechol and p-hydroquinone. These catalysts are also able to catalyse the oxidative bromination of salicylaldehyde to 5-bromosalicylaldehyde with ca. 80% selectively in the presence of aqueous 30% H2O2/KBr, a reaction similar to that exhibited by vanadate-dependent haloperoxidases. Their corresponding neat complexes have also been prepared and their catalytic activities have been compared.     

Dioxomolybdenum(VI) complexes as catalysts for the hydrosilylation of aldehydes and ketones

The dioxomolybdenum(VI) complexes [MoO2Cl2] (1), [MoO2(acac)2] (2), [MoO2(S2CNEt2)2] (3), [CpMoO2Cl] (4), [MoO2(mes)2] (5) and the polymeric organotin-oxomolybdates [(R3Sn)2MoO4] [R = n-Bu (6), t-Bu (7), Me (8)] were examined as catalysts for the hydrosilylation of aldehydes and ketones with dimethylphenylsilane. Of these, [MoO2Cl2] (1) was the most efficient catalyst, affording quantitative yields of the corresponding silylated ethers at room temperature in acetonitrile. Complexes 2, 4-8 also catalyzed the same reaction but required heating at 80 degrees C and longer reaction times compared with 1. Compound 3 is inactive. The wide scope of molybdenum oxide-mediated hydrosilylation was established with a variety of aldehydes and ketones. Counter intuitively, the activity of is 1 highest in NCMe. In the absence of a carbonyl substrate, [MoO2Cl2(NCBu(t))] (10) reacts with HSiMe2Ph affording [MoO(OSiMe2Ph)Cl2]2 (11) which has been fully characterized by NMR and IR spectroscopy, elemental analyses and mass spectrometry. Addition of radical scavengers strongly slows down the [MoO2Cl2]-based hydrosilylation suggesting the intermediacy of oxygen-centered radicals.     

Molybdenum oxides as highly effective dehydrative cyclization catalysts for the synthesis of oxazolines and thiazolines

In the presence of molybdenum oxide the dehydrative cyclization of N-acylserines, N-acylthreonines, and N-acylcysteines can be carried out under Dean-Stark conditions in toluene to give oxazolines and thiazolines. The ammonium salts (NH(4))(6)Mo(7)O(24).4H(2)O and (NH(4))(2)MoO(4) have excellent catalytic activities for the dehydrative cyclization of serine and threonine derivatives, and the acetylacetonate complex MoO(2)(acac)(2) has a remarkable catalytic activity for the dehydrative cyclization of cysteine derivatives. In addition, polyaniline-supported MoO(2)(acac)(2) can easily be recovered and reused.     

Molybdenum(VI) complexes of a 2,2'-biphenyl-bridged bis(amidophenoxide): competition between metal-ligand and metal-amidophenoxide π bonding

The 2,2'-biphenyl-bridged bis(2-aminophenol) ligand 4,4'-di-tert-butyl-N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-2,2'-diaminobiphenyl ((t)BuClipH(4)) reacts with MoO(2)(acac)(2) to form ((t)BuClipH(2))MoO(2), where the diarylamines remain protonated and bind trans to the terminal oxo groups. This complex readily loses water on treatment with pyridine or 3,5-lutidine to form mono-oxo complexes ((t)BuClip)MoO(L), which exhibit predominantly a cis-β geometry with an aryloxide trans to the oxo group. Exchange of the pyridine ligands is rapid and takes place by a dissociative mechanism, which occurs with retention of stereochemistry at molybdenum. Oxo-free alkoxide complexes ((t)BuClip)Mo(OR)(2) are formed from ((t)BuClipH(2))MoO(2) and ROH. Treatment of NMo(O(t)Bu)(3) with (t)BuClipH(4) results in complete deprotonation of the bis(aminophenol) and formation of a dimolybdenum complex ((t)BuClip)Mo(μ-N)(μ-NH(2))Mo((t)BuClip) containing both a bridging nitride (Mo-N = 1.848 ?, Mo-N-Mo = 109.49°) and a bridging amide group. The strong π bonding of this bis(amidophenoxide) ligand allows the molybdenum center to interconvert readily among species forming three, two, one, or zero π bonds from multiply bonded ligands.     

Optical absorption and NMR spectroscopic studies on paramagnetic neodymium(III) complexes with beta-diketone and heterocyclic amines. The environment effect on 4f-4f hypersensitive transitions

The optical absorption spectra of [Nd(acac)3(H2O)2].H2O, [Nd(acac)3bpy] and [Nd(acac)3phen(H2O)2] (where acac=acetylacetone, bpy=2,2'-bipyridyl and phen=1,10-phenanthroline) complexes in the visible region, in a series of non-aqueous solvents (methanol, ethanol, isopropanol, chloroform, acetonitrile, pyridine, nitrobenzene and dimethylsulphoxide) have been analyzed. The transition 4G(5/2)<--4I(9/2) (Nd-VI) located near the middle of the visible region (17,500 cm(-1)) is hypersensitive. Its behavior is in sharp contrast to many other typically weak and consistently unvaried, normal 4f-4f transitions. The oscillator strength of this transition for the chelate as well as its adducts with phen and bpy in any of the solvent employed is larger than the oscillator strength of Nd3+ aqua-ion. It is most intense in pyridine for all the complexes studied and, therefore, pyridine is the most effective in promoting f-f spectral intensity. The band shape and oscillator strength of the hypersensitive transitions display pronounced changes as compared to Nd3+ aqua-ion. The band shapes of the hypersensitive transitions show remarkable changes on passing from aqueous solution to various non-aqueous solutions, which is the result of change in the environment about the Nd(III) ion in the various solutions and suggests change in the environment about the Nd(III) ion in the various solutions and suggests coordination of solvent molecule(s), in some cases. A comparative account of hypersensitivity in the present complexes with those of other adducts of Nd(beta-diketoenolate)3 with heterocyclic amines is discussed. The NMR signals of heterocyclic amines have been shifted to high fields while the resonances due to acetylacetone moiety have moved to low fields. The paramagnetic shift in the complexes is dipolar in nature.     

Hydrothermal synthesis, structure and quantum chemistry of transition metal complex supported by metal-oxo cluster [{Ni(phen)2}2(x-Mo8O26)]

A nickel-1,10-phenanthroline complex supported on an octamolybdate, [{Ni(phen)2}2(x- Mo8O26)], has been hydrothermally synthesized with MoO3, H2MoO4, Ni(OAc)2· 6H2O and 1,10-phenathroline (1,10-phen) as raw materials. The crystals of the compound belong to monoclinic P21/n space group, a = 1.2952(2), b = 1.6659(10), c = 1.3956(12) nm, b =106.273(8)°, V = 2.8906(5) nm3, Z = 2. 5604 observable reflections (I ＞2s(I)) were used for structure resolution and refinements to converge to final R1 = 0.0414, wR2 = 0.0815. The result of structure determination shows that the compound contains octamolybdate possessing a novel structure type (named as x-isomer). The feature of x-[Mo8O26]4- is that it is composed of Mo6O6 ring and two MoO6 octahedra located at cap positions on opposite faces. The Mo6O6 ring contains two octahedral and four trigonal-bipyramidal MoVI atoms. Each x-[Mo8O26]4- unit is bonded with two [Ni(phen)2]2+ through terminal oxygen atoms of octahedral and neighbouring trigonal-bipyramidal Mo atom in the Mo6O6 ring. IR and UV-Vis spectra of the compound were measured and its electronic structure was studied by EHMO method.     

Selective oxidation of benzyl alcohols to benzaldehydes catalyzed by dioxomolybdenum Schiff base complex: synthesis,spectral characterization,crystal structure,theoretical and computational studies

Transition Metal Chemistry - A novel dioxomolybdenum Schiff base complex, MoO2L·DMF, was synthesized by treating MoO2(acac)2 with an ONO donor Schiff base ligand (H2L) derived by the...     

Reactivity studies of oxo-Mo(IV) complexes containing potential hydrogen-bond acceptor/donor phenolate ligands

Reactivity studies of oxo-Mo(IV) complexes, Tp(iPr)MoO{2-OC(6)H(4)C(O)R-κ(2)O,O'} (R = Me, Et, OMe, OEt, OPh, NHPh), containing chelated hydrogen-bond donor/acceptor phenolate ligands are reported. Hydrolysis/oxidation of Tp(iPr)MoO(2-OC(6)H(4)CO(2)Ph-κ(2)O,O') in the presence of methanol yields tetranuclear [Tp(iPr)MoO(μ-O)(2)MoO](2)(μ-OMe)(2) (1), while condensation of Tp(iPr)MoO{2-OC(6)H(4)C(O)Me-κ(2)O,O'} and methylamine gives the chelated iminophenolate complex, Tp(iPr)MoO{2-OC(6)H(4)C(Me)NMe-κ(2)O,N} (2), rather than the aqua complex, Tp(iPr)MoO{2-OC(6)H(4)C(Me)NMe-κO}(OH(2)). The oxo-Mo(IV) complexes are readily oxidized by dioxygen or hydrogen peroxide to the corresponding cis-dioxo-Mo(VI) complexes, Tp(iPr)MoO(2){2-OC(6)H(4)C(O)R}; in addition, suitable one-electron oxidants, e.g., [FeCp(2)]BF(4) and [N(C(6)H(4)Br)(3)][SbCl(6)], oxidize the complexes to their EPR-active (g(iso) ≈ 1.942) molybdenyl counterparts (3, 4). Molybdenyl complexes such as Tp(iPr)MoOCl{2-OC(6)H(4)C(O)R} (5) and Tp(iPr)MoOCl(2) also form when the complexes react with chlorinated solvents. The ester derivatives (R = OMe, OEt, OPh) react with propylene sulfide to form cis-oxosulfido-Mo(VI) complexes, Tp(iPr)MoOS{2-OC(6)H(4)C(O)R}, that crystallize as dimeric μ-disulfido-Mo(V) species, [Tp(iPr)MoO{2-OC(6)H(4)C(O)R}](2)(μ-S(2)) (6-8). The crystal structures of [Tp(iPr)MoO(μ-O)(2)MoO](2)(μ-OMe)(2), Tp(iPr)MoO{2-OC(6)H(4)C(Me)NMe}, Tp(iPr)MoOCl{2-OC(6)H(4)C(O)NHPh}·{2-HOC(6)H(4)C(O)NHPh}, and [Tp(iPr)MoO{2-OC(6)H(4)C(O)R}](2)(μ-S(2)) (R = OMe, OEt) are reported.     

Synthesis of ultrathin FePtPd nanowires and their use as catalysts for methanol oxidation reaction

We report a facile synthesis of ultrathin (2.5 nm) trimetallic FePtPd alloy nanowires (NWs) with tunable compositions and controlled length (<100 nm). The NWs were made by thermal decomposition of Fe(CO)(5) and sequential reduction of Pt(acac)(2) (acac = acetylacetonate) and Pd(acac)(2) at temperatures from 160 to 240 °C. These FePtPd NWs showed composition-dependent catalytic activity and stability for methanol oxidation reaction. Among FePtPd and FePt NWs as well as Pd, Pt, and PtPd nanoparticles (NPs) studied in 0.2 M methanol and 0.1 M HClO(4) solution, the Fe(28)Pt(38)Pd(34) NWs showed the highest activity, with their mass current density reaching 488.7 mA/mg Pt and peak potential for methanol oxidation decreasing to 0.614 V from 0.665 V (Pt NP catalyst). The NW catalysts were also more stable than the NP catalysts, with the Fe(28)Pt(38)Pd(34) NWs retaining the highest mass current density (98.1 mA/mg Pt) after a 2 h current-time test at 0.4 V. These trimetallic NWs are a promising new class of catalyst for methanol oxidation reaction and for direct methanol fuel cell applications.     

Synthesis, characterisation, reactivity and in vitro antiamoebic activity of hydrazone based oxovanadium(IV), oxovanadium(V) and mu-bis(oxo)bis{oxovanadium(V)} complexes

Binuclear, mu-bis(oxo)bis{oxovanadium(V)} complexes [(VOL)2(mu-O)2](2 and 7)(where HL are the hydrazones Hacpy-nah I or Hacpy-fah II; acpy = 2-acetylpyridine, nah = nicotinic acid hydrazide and fah = 2-furoic acid hydrazide) were prepared by the reaction of [VO(acac)2] and the ligands in methanol followed by aerial oxidation. The paramagnetic intermediate complexes [VO(acac)(acpy-nah)](1) and [VO(acac)(acpy-fah)](6) have also been isolated. Treatment of [VO(acac)(acpy-nah)] and [VO(acac)(acpy-fah)] with aqueous H2O2 yields the oxoperoxovanadium(V) complexes [VO(O2)(acpy-nah)](3) and [VO(O2)(acpy-fah)](8). In the presence of catechol (H2cat) or benzohydroxamic acid (H2bha), 1 and 6 give the mixed chelate complexes [VO(cat)L](HL =I: 4, HL =II: 9) or [VO(bha)L](HL =I: 5, HL =II: 10). Complexes 4, 5, 9 and 10 slowly convert to the corresponding oxo-mu-oxo species 2 and 7 in DMF solution. Ascorbic acid enhances this conversion under aerobic conditions, possibly through reduction of these complexes with concomitant removal of coordinated catecholate or benzohydroxamate. Acidification of 7 with HCl dissolved in methanol afforded a hydroxo(oxo) complex. The crystal and molecular structure of 2.1.5H2O has been determined, and the structure of 7 re-determined, by single crystal X-ray diffraction. Both of these binuclear complexes contain the uncommon asymmetrical {VO(mu-O)}2 diamond core. The in vitro tests of the antiamoebic activity of ligands I and II and their binuclear complexes 2 and 7 against the protozoan parasite Entamoeba histolytica show that the ligands have no amoebicidal activity while their vanadium complexes 2 and 7 display more effective amoebicidal activity than the most commonly used drug metronidazole (IC50 values are 1.68 and 0.45 microM, respectively vs 1.81 microM for metronidazole). Complexes 2 and 7 catalyse the oxidation of styrene and ethyl benzene effectively. Oxidation of styrene, using H2O2 as an oxidant, gives styrene epoxide, 2-phenylacetaldehyde, benzaldehyde, benzoic acid and 1-phenyl-ethane-1,2-diol, while ethyl benzene yields benzyl alcohol, benzaldehyde and 1-phenyl-ethane-1,2-diol.