- Selective oxidation of sulfides to sulfoxides in water using 30% hydrogen peroxide catalyzed with a recoverable VO(acac)2 exchanged sulfonic acid resin catalyst
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Various types of sulfides are selectively oxidized to sulfoxides in good to excellent yields in aqueous media using 30% aqueous hydrogen peroxide as an oxidant in the presence of catalytic amounts of a VO(acac)2-exchanged strongly acidic polymeric resin catalyst in water at room temperature. The catalyst can be recovered and reused at least five times without loss of activity and selectivity.
- Prasanth, K. Leon,Maheswaran
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- Thermal Stability of Substituted Pyridine Adducts of Bis(acetylacetonato)-oxovanadium(IV) in Solid State
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The kinetic of the elimination reaction of axial ligand B in 2B> complexes (Hacac = acetylacetone;B = pyridine, its derivatives, and ammonia) was studied in solid state by the Coats-Redfern method.The frequency factor and activation en
- Shibutani, Yasuhiko,Shinra, Koichiro
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- Volatility and thermal stability of vanadyl β-diketonate complexes
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Thermal behavior and thermodynamic characteristics of vanadyl β-diketonates—acetylacetonate VO(acac)2, dipivaloylmethanate VO(thd)2, and tris-hexafluoroacetylacetonate VO(hfa)2 (Hacac, 2,4-pentanedione; Hthd, 2,2,6,6-tetra
- Malkerova,Makarevich,Alikhanyan,Kuz’mina
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- Composition and geometry of oxovanadium(IV) and (V)-aminoethanol-Schiff base complexes and stability of their peroxo complexes in solution
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Vanadium(IV) and (V) complexes (VO(sal-ae)) with Schiff bases prepared from 2-aminoethanol and salicylaldehyde and its derivatives have been synthesized and characterized in solid and in solution by EPR, IR, and UV-Vis spectroscopy. The complexes of both V(IV) and V(V) contain bridges (V-O-V) by alkoxy oxygens(oxo) in the solid state. The complexes of V(IV) in dichloromethane are binuclear,in which two alkoxy oxygens serve as bridges between the two metal atoms. They are mononuclear with one solvent ligated in the equatorial plane in each complex in dimethyl sulfoxide and methanol. The extent of the formation and the stability of organic hydroperoxide complexes of V(V) prepared from the V(IV)-Schiff base complexes increase with decreasing donor number of the solvent. The difference in electron-donating and withdrawing ability of the substituent groups affects the A∥ values for the V(IV)-Schiff base complexes in DMSO.
- Ando, Ryuji,Nagai, Mayumi,Yagyu, Takeyoshi,Maeda, Masunobu
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- Giant spin-phonon bottleneck effects in evaporable vanadyl-based molecules with long spin coherence
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Vanadium(iv) complexes have recently shown record quantum spin coherence times that in several circumstances are limited by spin-lattice relaxation. The role of the environment and vibronic properties in the low temperature dynamics is here investigated by a comparative study of the magnetization dynamics as a function of crystallite size and the steric hindrance of the β-diketonate ligands in VO(acac)2 (1), VO(dpm)2 (2) and VO(dbm)2 (3) evaporable complexes (acac- = acetylacetonate, dpm- = dipivaloylmethanate, and dbm- = dibenzoylmethanate). A pronounced crystallite size dependence of the relaxation time is observed at unusually high temperatures (up to 40 K), which is associated with a giant spin-phonon bottleneck effect. We model this behaviour by an ad hoc force field approach derived from density functional theory calculations, which evidences a correlation of the intensity of the phenomenon with ligand dimensions and the unit cell size.
- Tesi,Lunghi,Atzori,Lucaccini,Sorace,Totti,Sessoli
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- Immobilized some of vanadium compounds on modified graphene oxide as nanofiber network for epoxidation of allyl alcohols
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VO(acac)2 and the in situ generated VO(Salen) complex were immobilized on the covalently modified graphene oxide (GO) with ethylenediamine (en) and designated as VO(acac)2@en-GO and VO@Salen@en-GO, respectively. Characterization of the prepared compounds was carried out with FT-IR, XRD, ICP, CHN, Raman, SEM, TEM, and BET techniques. The SEM results confirmed the formation a nanofiber network and nanointerconnected needles. The prepared immobilized complexes were then used as heterogeneous catalysts for epoxidation of some allyl alcohols such as geraniol, trans-2-hexene-1-ol, and 1-octen-3-ol. Based on the results obtained by GC and GC–mass analyses, epoxidation of geraniol with 97% conversion and 100% selectivity seemed promising. Readily recycling of the catalyst and reusing for four successive catalytic runs without significant loss of activity revealed that this catalysis system deserves nomination for practical application.
- Farzaneh, Faezeh,Ahmadi, Zahra,Azarkamanzad, Zahra,Ghahremani, Maryam
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- Performance of a non-aqueous vanadium acetylacetonate prototype redox flow battery: Examination of separators and capacity decay
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Non-aqueous electrolytes are stable over wide electrochemical potential windows, generally a critical component that to a great extent determines the performance of RFB systems for practical applications. In this work, the performance of a RFB was evaluated with Nafion 1035 membranes and Daramic 175 SLImicroporous separators. The non-aqueous electrolyte was based on vanadium (III) acetylacetonate. This chemistry possesses two couples over ～2.2 V. Charge-discharge cycles were performed in a RFB at a current density of 10 mA cm-2. Coulombic and energy efficiencies of 91% and 80% were achieved using the Nafion membrane. A similar RFB using the Daramic microporous separator achieved columbic and energy efficiencies of 73% and 68%, respectively. The source of capacity decay during multiple charge-discharge cycles was also investigated. The loss in the capacity was related to the poor chemical stability of the vanadium acetylacetonate in the positive electrolyte during battery cycling.
- Escalante-Garca, Ismailia L.,Wainright, Jesse S.,Savinell, Robert F.,Thompson, Levi T.
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- New oxovanadium(IV) complexes with mixed ligands - Synthesis, thermal stability, and crystal structure of (VO)2(acac)2(μ-OEt) 2 and (VO)2(thd)2(μ-OEt)2
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Synthesis, crystal structure, thermal stability, and magnetic properties of the new oxovanadium(IV) complexes [(VO)2L2(μ-OEt) 2] with mixed β-diketonato [L = acac = C5H 7O2 or L = thd = C11H19O 2-] and ethanolato (OEt) ligands are reported. The structure determinations of (VO)2(acac)2(μ-OEt) 2 [P21/c, with a = 14.775(2), b = 8.788(1), c = 15.742(2) A, β = 112.43(1)°] and (VO)2(thd)2(μ- OEt)2 [P1, with a = 8.871(3), b = 9.988(4), r = 10.299(4) A, α = 73.51(1), β = 68.70(1), γ = 65.85(1)°] are based on single-crystal X-ray diffraction data collected at 105 K. Structure data for VO(acac)2 and VO(thd)2 are redetermined at 105 and 295 K. (VO)2(acac)2(μ-OEt)2 and (VO) 2(thd)2(μ-OEt)2 comprise binuclear five-coordinated molecular units. The configuration of five oxygen atoms around a central vanadium atom is approximately square pyramidal in all the four studied complexes. (VO)2(thd)2(μ-OEt)2 exhibits conspicuous changes in unit-cell dimensions (expansion in a and c, shrinkage in b, and appreciable variation in α, β, and γ) on going from 105 to 295 K, which appear to reflect adjustments in the configuration of its (anti-arranged) ligands. The interatomic distances in the crystal structures are analyzed in terms of the bond-valence concept. The four-valent state of vanadium is verified by magnetic susceptibility measurements. All complexes are subject to sublimation.
- Ahmed,Fjellvag,Kjekshus,Klewe
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- Oxovanadium(IV), copper(II) or cobalt(II) acetylacetone complexes immobilized on amino-functionalized CMK-3 for the aerobic epoxidation of styrene
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Oxovanadium(IV), copper(II) and cobalt(II) acetylacetone complexes have been grafted onto amino-modified CMK-3-O (VO-NH2-CMK-3, Cu-NH2-CMK-3 and Co-NH2-CMK-3,respectively) and the materials thus prepared were used as heterogeneous catalysts for the aerobic oxidation of styrene. X-ray diffraction, nitrogen adsorption-desorption and transmission electron microscopy measurements confirmed the structural integrity of the mesoporous hosts, and spectroscopic characterization techniques (Fourier transform infrared, X-ray photoelectron, Raman) and thermogravimetry confirmed the ligands and the successful anchoring of the acetylacetone complexes to the modified mesoporous support. VO-NH2-CMK-3 displayed a relatively good catalytic performance with 94.6% of styrene conversion using air as oxidant, while Cu-NH2-CMK-3 gave 99.6% of styrene conversion using tert-butyl hydroperoxide as oxidant.
- Wang, Xiufang,Wu, Shujie,Li, Zhifang,Yang, Xiaoyuan,Hu, Jing,Huo, Qisheng,Guan, Jingqi,Kan, Qiubin
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p. 698 - 706
(2015/09/28)
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- Heterogeneous catalytic oxidation of styrene by an oxo bridged divanadium(V) complex of an acetohydrazide-Schiff base
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We have synthesized a μ-oxido divanadium compound [(VOL) 2(μ-O)] with an aliphatic hydrazone ligand LH2 = (E)-N'-(1-(2-hydroxyphenyl)ethylidene)acetohydrazide. The complex was characterized by elemental analysis, IR and UV-Vis spectroscopy and the molecular structure was established by single crystal X-ray diffraction technique. The complex has been infused over alumina to prepare a heterogeneous catalyst which was characterized by IR spectroscopy, thermogravimetric and powder XRD analyses. The catalyst has been studied for the oxidation of styrene in presence of H2O2 and appears to be easily recyclable. A conversion of 99.7% and selectivity of 88.1% for benzaldehyde formation and a turnover number of 1354 was detected under the most favorable reaction conditions.
- Sadhukhan, Dipali,Maiti, Monami,Zangrando, Ennio,Pathan, Soyeb,Mitra, Samiran,Patel, Anjali
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- The direct electrochemical synthesis of transition metal acetylacetonates
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Acetylacetonates were prepared electrochemically in good yield using the pure liquid ligand, acetylacetone, as the solvent, in which the supporting electrolyte, tetra-n-butyammonium hexafluorophosphate, was dissolved; the metal of interest served as the electrodes. The products were characterized by UV-visible spectrometry (color) and mass spectrometry. Both a lower, M(AcAc)2, and a higher, M(AcAc)3, oxidate state were formed for the cobalt and manganese systems; the identity of the product(s) could be biased by a careful choice of the potential used for the synthesis.
- Long,Lagowski
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p. 813 - 815
(2008/10/09)
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- Reactions of transition-metal oxo complexes with B(C6F5)3: Crystal structures of [V{OB(C6F5)3}(acac)2], [Ti{OB(C6F5)3}(acac)2] and cis-[MoO{OB(C6F5)3}(acac)2] (acac = acetylacetonate)
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The transition-metal pxo complexes [VO(acac)2], [{TiO(acac)2}2] and cis-[MoO2(acac)2] (acac = C5H7O2) reacted with the strong Lewis acid B(C6F5)3 to give the structurally characterized complexes [V{OB(C6F5)3}(acac)2], [Ti{OB(C6F5)3}(acac)2] and cis-[MoO{QB(C6F5)3}(acac)2]. The M=O-B moiety is essentially linear.
- Galsworthy, Jane R.,Green, Malcolm L. H.,Mueller, Matthias,Prout, Keith
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p. 1309 - 1313
(2007/10/03)
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- The Formation of 1,4-Quinones by Oxovanadium(IV)-Complexes Catalyzed Aerobic Oxygenation of Fused Aromatic Compounds
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In the presence of a catalytic amount of oxovanadium(IV) complexes coordinated with 1,3-diketone ligands, fused aromatic compounds such as naphthalenes and naphthol derivatives are smoothly oxygenated into the corresponding 1,4-naphthoquinones by combined use of molecular oxygen and crotonaldehyde under an atmospheric pressure.
- Takai, Toshihiro,Hata, Eiichiro,Mukaiyama, Teruaki
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p. 885 - 888
(2007/10/02)
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- Molecular vapor synthesis: The use of titanium monoxide and vanadium monoxide vapors as reagents
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The production and reactivity of titanium monoxide (TiO) and vanadium monoxide (VO) on a synthetically useful scale were studied by using the techniques and apparatus previously developed for reactions of metal atoms. Cocondensation reactions with chlorine showed that greater amounts of metal atoms were produced as impurities in the vapor when stoichiometric metal monoxides were used as vapor sources than when metal sesquioxides were used. It was found that evaporation of MO and M2O3 solids from open tungsten boats yielded vapor compositions of M, MO, and MO2 similar to those reported earlier from Knudsen cells in the case of vanadium but somewhat different in the case of titanium. The monoxide molecules reacted with chlorine to produce oxometal chlorides in high yields. They reacted with 2,4-pentanedione and other organics containing relatively acidic hydrogen, to form water as a byproduct via protonation of the oxo moiety; coordination compounds of titanium and vanadium were isolated as acac complexes in high yields.
- Groshens, Thomas J.,Klabunde, Kenneth J.
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p. 2979 - 2982
(2008/10/08)
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- Epoxidation of Olefins with Molecular Oxygen and Alcohol Catalyzed by Bis(2-alkyl-1,3-diketonato)oxovanadium(IV)
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By combined use of molecular oxygen (oxidant) and secondary or primary alocohol (reductant) in the presence of a catalytic amount of bis(2-alkyl-1,3-diketonato)oxovanadium(IV) complexes, norbornene analogues are monooxygenated into the corresponding epoxides in good yields.
- Takai, Toshihiro,Yamada, Tohru,Mukaiyama, Teruaki
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p. 1657 - 1660
(2007/10/02)
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- PREPARATION, CHARACTERIZATION AND REACTIONS OF VANADIUM(IV) beta -DIKETONATE COMPLEXES.
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The beta -diketone complexes of vanadium(IV), VO(dik)//2 (where dik EQUVLNT btfac, tfac, ttfac, acac, bzac and bzbz) have been prepared either by the reaction of vanadium pentoxide with the appropriate ligand in toluene under reflux for 24 h or by the reaction of a warm aqueous or ethanolic solution of vanadium sulphate with the ligand. The oxovanadium(IV) complexes react with sulphur oxide dichloride and dibromide and phosphorus pentachloride to form dihalovanadium(IV) diketonate complexes. These compounds have been characterized by elemental analysis, melting point measurements, IR and Raman spectra, magnetic susceptibility measurements, electron spin resonance (ESR) and mass spectral studies and X-ray powder diffraction.
- Behzadi,Thompson
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p. 281 - 296
(2008/10/08)
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