- Mixed ligation to vanadium(III): Synthesis, spectra and structures of bis(acetylacetonato)(o-phenanthroline)vanadium(III) fluoroborate and bis(acetylacetonato)(o-phenanthroline)vanadium(III) perchlorate
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Two mixed ligand vanadium(III) complexes bis(acetylacetonato) (phenanthroline)vanadium(III) fluoroborate (1) and bis(acetylacetonato) (phenanthroline)vanadium(III) perchorate (2) have been prepared and characterized by UV-Vis, IR, 1H NMR spectroscopic techniques and single crystal X-ray diffraction. The electronic spectra are as expected for V(III) in an octahedral environment. The 1H NMR spectra are typical of paramagnetic V(III) species. The complexes have crystallized with dichloromethane solvate and are isomorphous. The coordination sphere is composed of vanadium in a distorted octahedral environment, ligated to two bidentate chelating acetylacetonate ligands through the oxygen atoms and two phenanthroline nitrogens.
- Kavitha, Savaridasson Jose,Panchanatheswaran, Krishnaswamy,Elsegood, Mark R.J.,Dale, Sophie H.
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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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- Redox reactions with bis(η6-arene) derivatives of early transition metals
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The reactivity of M(η6-arene)2 derivatives of early transition metals (M = Ti, Cr, Mo, arene = MeC6H5; M = V, Nb, arene = 1,3,5-Me3C6H3) has been investigated and the syntheses of new and known compounds are described. The derivatives M(CH3COO)3, M = Ti, V, Nb, Cr; M(CF 3COO)3, M = Ti, Nb, Cr; M(acac)3, M = Ti, V, Mo, acac = acetylacetonato, and M(F6acac)3, F 6acac = hexafluoroacetylacetonato, M = V, Nb have been prepared by reaction of the metal bis(arene) derivatives with the appropriate Lewis acid. The crystal and molecular structure of V(F6acac)3 has been determined. Hydrogen halides or halogens react with M(η6-arene) 2 with formation of metal halides, a highly reactive form of VCl 3 being obtained from V(η6-1,3,5-Me3C 6H3)2 and hydrogen chloride in heptane. TiCl4 oxidizes Ti(η6-arene)2 with complete loss of the arene ligands. An electron transfer process affording ionic derivatives of formula [M(η6-MeC6H5) 2][TiCl4(THF)2], M = Cr (structurally characterized), Mo, has been observed between the THF-adduct of TiCl4 and the appropriate metal-arene derivative of Group 6.
- Calderazzo, Fausto,Englert, Ulli,Pampaloni, Guido,Volpe, Manuel
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p. 3321 - 3332
(2007/10/03)
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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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- Electrochemical Synthesis, IX - Preparation of CO Free Metal Complexes
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The electrochemical synthesis of metal acetylacetonates (M = Cr, Mo, V, Ti) from metal anodes and acetylacetone is reported.In the presence of oxygen the oxo compounds OM(acac)2 are formed for M = Mo, V and Ti instead of M(acac)3.The electrochemical production of Ni(PPh3)4 and Fe(PMe3)4 starting from Ni(acac)2 and Fe metal, respectively, has been investigated.Successful carbonylation to Ni(CO)n(PPh3)4-n (n = 1,2) or Fe(CO)m(PMe)5-m (m = 2,3) proves the hypothesis that replacement of PR3 ligands by CO takes place after reduction of the central metal to the oxidation state 0. - Key words: Electrochemical Synthesis, Transition Metal Complexes, Acetylacetonates, Phosphane Complexes, High Pressure Carbonylation
- Grobe, Joseph,Zimmermann, Heinz
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p. 808 - 811
(2007/10/02)
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- Kinetics and mechanism of ligand isotopic exchange of tris(acetylacetonato)vanadium(III) in acetylacetone and in organic solvents
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Tris(acetylacetonato)vanadium(III) undergoes ligand exchange in acetylacetone (Hacac) at 25-40°C without side reactions. The exchange rate is expressed by rate = (ka + kb[H2O])[complex] ([complex] ≈ 0.005 M, [H2O] = 0.01-0.2 M; M = mol dm-3); ka = (1.36 ± 0.12) × 10-4 s-1 and kb = (6.6 ± 1.5) × 10-4 M-1 s-1 at 25°C. The ΔH? and ΔS? are 17.5 ± 0.4 and 18.0 ± 1.3 kcal mol-1 and -17.5 ± 1.3 and -12.6 ± 1.3 cal K-1 mol-1, respectively (cal = 4.18 J). No deuterium isotope effect was observed on the rate. Linear plot of k0 vs. the concentration of free Hacac in acetonitrile and in neat Hacac suggests the predominant participation of the enol tautomer in the exchange. The rate-determining step seems to correspond to the formation of an intermediate containing a one-ended acac- and an Hacac (enol) or a water molecule for the ka or kb path, respectively, by the associative mechanism. The rate of exchange in dimethyl sulfoxide, acetonitrile, chloroform, methanol, and ethanol increased in this sequence by a factor of 103. The acceptor number of these solvents appears to be responsible for the different rates of exchange.
- Watanabe, Aiji,Kido, Hiroaki,Saito, Kazuo
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p. 1107 - 1111
(2008/10/08)
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