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The Preparation Reactivity and Structures of Law Oxidation State Vanadium Complexes in Relation to Nitrogen Fixation.

Holt, David Gary Lawton. (1990) The Preparation Reactivity and Structures of Law Oxidation State Vanadium Complexes in Relation to Nitrogen Fixation. Doctoral thesis, University of Surrey (United Kingdom)..

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Hydrated vanadium(II) salts have previously been prepared by electrochemical reduction of the corresponding vanadyl(IV) salts, and [V(H2O)6]SO4, [VCl2(H20)4] and [V(H2O)6]Br2 were prepared in this way. In a search for more convenient methods, a brief report that pure vanadium powder will dissolve in aqueous HCl, HBr, HI, HBF4 or H2SO4 to give vanadium(II) salts was re-investigated. It was confirmed that [VCl2(H2O)4], [V(H2O)6]Br2 and [V(H2O)6] (BF4)2 could be obtained, but not the iodide or the sulphate. The new compound [V(H2O)6] (CF3SO3)2 was similarly prepared from vanadium and trifluoromethanesulphonic acid. X-ray analysis of [V(H2O6] (CF3SO3)2 has shown that the cations are regular octahedra and are extensively hydrogen-bonded to the anions throughout the lattice. Vanadium metal has also been shown to react with HX gas (X = Cl or Br) dissolved in acetic acid, formic acid and methanol. The novel vanadium(II) complexes containing coordinated acetic acid [VCl2(CH3COOH)4] and [V(CH3COOH)6]Br2 have been isolated from acetic acid, and X-ray analysis reveals that the acetic acid is coordinated through the carbonyl oxygen and not through the hydroxyl oxygen. There is considerable intramolecular hydrogen-bonding in trans-[VCl2(CH3COOH)4] and intermolecular hydrogen-bonding in [V(CH3COOH)6]Br2. From formic acid and methanol respectively the vanadium(III) complexes [VCl3(HCOOH)3] and [VCl3(CH3OH)3] were isolated. From reactions of the vanadium(II) halides with the di-tertiary phosphines 1,2-bis(dimethylphosphino)ethane (dmpe) or 1,2-bis(diethylphosphino)ethane (depe) the vanadium(II) complexes, [VX2(P)2] (X = Cl, Br or I and P = dmpe or depe), have been obtained. The complexes [VX2(dppe)2]. 2thf (X = Cl or Br) were isolated from reactions between 1,2-bis(diphenylphosphino)ethane (dppe) and the new starting materials [VX2(CH3OH)(thf)] (X = Cl or Br). No products could be isolated from dppe when [VCl2(H2O)4] or [V(H2O)6]Br2 were used in the preparation. [VCl2(depe)2] and [VCl2(dppe)2] . 2thf were examined by single crystal X-ray crystallography and found to have trans-octahedral structures. All the vanadium(II) complexes were shown to have effective magnetic moments of ca 3. 9 UB independent of temperature, thus confirming the oxidation state. Reactions of the vanadium(II)-ditertiary phosphine complexes with carbon monoxide, dinitrogen and dihydrogen in the presence of sodium amalgam or sodium naphthalene, and with chlorine and bromine were investigated. Many solids were isolated, unfortunately none of them could be characterised. The vanadium(III) complexes [VCl3(PMe2Ph)3], [VBr3(PMe2Ph)3], [VCl3(PEt2Ph)2], [VBr3(PEt2PH)3] and [VCl3(PPr2Ph)3] have been prepared from reactions between [VX3(thf)3] (X = Cl or Br) and the tertiary phosphine.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Holt, David Gary Lawton.
Date : 1990
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1990.
Depositing User : EPrints Services
Date Deposited : 30 Apr 2019 08:08
Last Modified : 20 Aug 2019 15:32

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