Paramagnetic Resonance Studies of Bonding in Vanadyl and Molybdenyl Metal Complexes

DeArmond, Keith; Garrett, B. B.; Gutowsky, H. S.

doi:10.1063/1.1696036

Cited by 122 publications

(38 citation statements)

References 32 publications

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“…It has, in fact, been found to possess a symmetry closer to C 2v with the vanadium above the equatorial plane and the two acetylacetonate skeletons following the vanadium out-of-plane and meeting 22 at 163°. Consequently, the equations relating the spin Hamiltonian parameters to the LCAO-MO theory of d 1 ions with C 4v symmetry presented by DeArmond et al 23 (analogous to those discussed above for Cu complexes in D 2h symmetry) are inappropriate. Nevertheless, the relatively small anisotropy in g xx and g yy and in A xx and A yy (Table 1) indicate that the ground state remains almost exclusively of d xy character, expected for strictly C 4v symmetry.…”

Section: Bonding Parametersmentioning

confidence: 97%

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An unusual temperature dependence of the EPR parameters of copper(II) and oxovanadium(IV) bis(acetylacetonate) complexes

et al. 1999

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Section: Bonding Parametersmentioning

confidence: 97%

“…23 The values of˛2 for the vanadyl complex, characterizing in-planebonding in this case, at 270 and 120 K are given in Table 2. The value of 0.66 at 270 K is indicative of a high degree of covalent bonding and contrasts with that of the Cu complex (0.82).…”

Section: Vo(acac)mentioning

confidence: 99%

An unusual temperature dependence of the EPR parameters of copper(II) and oxovanadium(IV) bis(acetylacetonate) complexes

et al. 1999

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“…Six-coordinated VOCl 5 3-ion (distorted octahedron, C 4v symmetry) was characterized in crystalline matrixes. 24,25 Electronic absorption spectra of this species exhibited a maximum around 15500 cm −1 and a shoulder around 16200 cm 31 Spectral curves reported in these studies contained a high intensity maximum at 13000-14300 cm −1 , and in some cases a weak overlapping band at 11600-12100 cm −1 . Moreover the presence of VOCl 4 2− is proved by EXAFS.…”

Section: Spectra Of Vanadium(iii) Ions-vanadium(iii)mentioning

confidence: 98%

Vanadium Speciation in Fused Alkali Chlorides

Polovov

Чернышов

Volkovich

et al. 2017

J. Electrochem. Soc.

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Electronic absorption spectra of vanadium ions were recorded between 450 and 750 • C in 3LiCl-2KCl, NaCl-KCl and NaCl-2CsCl based melts. Analysis of the spectra showed that vanadium in the oxidation states of +2 and +3 is present in the melts as complex chloro-ions. Vanadium(II) can form the complex ions in octahedral and tetrahedral coordination, the latter being favored by higher temperatures. Only six-coordinated V(III) ions were observed. Vanadium in the oxidation state of +4 can be present in chloride melts only in the form of vanadyl-based oxochloro-species. Main spectroscopic parameters of vanadium complex ions were determined. Electronic absorption spectroscopy was also applied for studying a variety of the red-ox processes in vanadium containing melts including electrochemical oxidation and reduction of various species, and reaction of vanadium containing melts with oxygen. Vanadium has many attractive properties including high creep strength, excellent strength-to-weight ratio, resistance to corrosion, low neutron cross-section, high thermal conductivity, etc.1 Due to these unique set of properties vanadium is used in non-ferrous and ferrous metallurgy as a component of titanium-based alloys for the aerospace industry and for manufacturing special steels. 2,3High-purity vanadium metal is required for manufacturing alloys for nuclear fusion applications, superconducting and hydrogen-storage materials.4-6 Vanadium on industrial scale is produced by aluminum or carbon reduction of oxides or magnesium reduction of vanadium chlorides. [7][8][9] To obtain the high-purity metal, the crude material is refined by vacuum melting or electrolysis in molten chlorides.10 Electrolytic refining is effective in removing most of metallic and nonmetallic impurities, i.e. aluminum, magnesium, iron, carbon, nitrogen, oxygen, silicon, etc. Understanding vanadium speciation in chloride melts is essential for designing or optimizing an industrial electrochemical process.Vanadium is a polyvalent metal and, as for many d-element ions with partially filled d-orbitals, electronic absorption spectroscopy was employed for characterization of vanadium species in fused salts. In molten salts vanadium is capable of forming the ions containing the element in oxidation states +2, +3, +4 and +5. First electronic absorption spectra (EAS) of vanadium-containing melts were recorded over a half of a century ago in LiCl-KCl eutectic, KAlCl 4 and Cs 2 ZnCl 4 , [11][12][13][14] followed by KSCN based melts. 15,16 Subsequent studies included other alkali chloride mixtures. [17][18][19][20] Analysis of the data present in the literature showed that there is a considerable controversy about the stable oxidation states of vanadium and the coordination geometry of its complex ions in the lower oxidation states in molten alkali chlorides. Vanadium in the oxidation states +2 and +3 was said to form complex ions where the metal is coordinated to six or four anions in octahedral or tetrahedral geometry, respectively. In the higher oxidation states, +4 a...

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“…equation (2) for g || and g ? do not require the consideration of the contribution of the spin-orbital bond of oxide ligands [33] because of its low value. The selection of the k value for Mo 5+ ions was performed based on the data for vanadium ions [34], where the transfer from V 4+ to VO 2+ with formation of vanadyl bond led to the decrease of the k value by ca.…”

Section: Uv-vis Studymentioning

confidence: 99%

Effect of thermal treatment on states of molybdenum in Mo/H?ZSM-5 catalyst for methane dehydroaromatization: ESR and UV?VIS study

et al. 2005

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Valence and coordination states of molybdenum ions formed upon thermal treatment of Mo/H-ZSM-5 catalyst for methane dehydroaromatization in Ar and Ar/CH 4 media at 573-973 K have been studied by ESR and UV-VIS spectroscopy. For comparison, the characteristic ESR spectra of thermolyzed bulk ammonium heptamolybdate have been studied and analyzed in detail. The nature of earlier observed Mo 5+ ions has been verified, and new paramagnetic states of molybdenum in Mo/H-ZSM-5 catalysts have been detected: Mo 3+ ions, and Mo 5+ ions in tetrahedral coordination with delocalization of unpaired electron to Al and H or Al and N atoms.

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Paramagnetic Resonance Studies of Bonding in Vanadyl and Molybdenyl Metal Complexes

Cited by 122 publications

References 32 publications

An unusual temperature dependence of the EPR parameters of copper(II) and oxovanadium(IV) bis(acetylacetonate) complexes

An unusual temperature dependence of the EPR parameters of copper(II) and oxovanadium(IV) bis(acetylacetonate) complexes

Vanadium Speciation in Fused Alkali Chlorides

Effect of thermal treatment on states of molybdenum in Mo/H?ZSM-5 catalyst for methane dehydroaromatization: ESR and UV?VIS study

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