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Vanadium, Niobium and Tantalum

4 Vanadium, Niobium and Tantalum The metal-metal coupling and metal-ligand [Pg.326]

3 Vanadium, Niobium and Tantalum.- A number of reports of reactions involving the cyclopentadienyl ring have been made. [Pg.363]

Reactions involving migration of groups to the Cp ring include [Pg.363]

CP2VR reacting with CO to give (22). Loss of a Cp ring occurs [Pg.363]

A study of insertion/6-elimination reactions has been made 141 [Pg.365]

Earlier reference has been made to vibrational studies on V(acac)3 and (Ta205)i-.(Ti02)x.  [Pg.244]

The value of vV = 0 is higher in V0(quin)(H20)3 (987 cm ) than in [V0(quin)2(S04)] (960 cm ), where quin = quinic acid, (2), due to the effects of sulfato coordination. vV = O modes were assigned for a range of V (0)N2S2 and V (0)S4 systems, consistent with some degree of magnetic interaction in these compounds.  [Pg.244]

The complexes OV (L), where L = iV,0-donor polyfunctional ligands, e.g. iV,iV-bis-(2-hydroxybenzyl)-JV-(2-pyridylmethyl)-JV -(2-hydroxyethyl)ethyl-enediamine, have had vV = 0 modes assigned from their IR spectra. VO(5-N02-salen), where 5-N02-salen = iV,JV -di-5-nitrosalicylidene-l,2-ethane diamine, has vV = 0 at 875 cm h Oxidation of [V(0)(C8H4S8)2] , where the ligand = (3), to V(0)(CsH4S8)2 leads to a shift in vV = O from 953 to 991 cm . The latter is characteristic of V(V), i.e. some oxidation has occurred at the metal centre.  [Pg.244]

FTIR spectra of V04 in calcium phosphate/vanadate solid solutions show that V04 has C3V site symmetry at low vanadium contents, compared to Cs for pure vanadate. IR spectroscopy was used to characterise iron-containing CeV04 films (using vV = O at 770 cm ).  [Pg.245]

IR bands due to vVO were used to identify potassium-containing V2O5 catalysts. It was suggested that the V = O species was responsible for dehydrogenation reactions. Similar IR bands were used to characterise V20s-Zr02 catalysts.  [Pg.245]

FTIR and DRIFTS studies were used to characterise the structures of silica-supported VOx species. vVO modes were used to monitor redox behaviour of a P-VOPO4 catalyst. FTIR of a vanadium oxide/ZSM-5 zeolite suggests the presence of the species (Si-0)3V=0, of C3V symmetry. TR measurements were used to probe the lowest electronically-excited state of (TPP)V=0.  [Pg.277]

A relationship has been established between bond stretching wavenumbers and internal bonding for vanadates in aqueous solution.The Raman spectrum of the myosin Sl-MyADP-vanadate complex shows vanadate bands at 870, 844 and 829 cm - consistent with an approximately planar unit. Raman [Pg.278]

The resonance Raman spectra of [ML2], where M = V, Fe or Co, L = (2-thiophenyl)bis(pyrazolyl)methane, gave assignments and excitation profiles for vMS. The wavenumbers were (M = V) 303, 319 cm (Fe) 315, 325 cm (Co) 312, 333 cm K ° The IR spectra of V2S202(CuPPh3)4[Cu(MeCN)2] and related clusters gave assignments to vVS modes. [Pg.279]

The complex V2( J.,r -thffo)2Cl202, where thffo = 2-tetrahydrofurfuroxide, has vVCl bands in the IR spectrum at 380 and 360 cm. VBr3([9]aneS3) shows vVBr at 306 cm ([9]aneS3 = 1,4,7-trithiacyclononane).  [Pg.279]

Interest in the Vanadium group (relevant to this report) is limited. Rest has continued to probe the photochemistry of half-sandwich tetracarbonylvanadium complexes in low-temperature matrices. Also at low temperature, the [Pg.146]

Photodissociation of the transition-metal cluster ion VFe provides an indirect measure of the absorption spectrum of the lon. Matrix photolysis of M(Tj -CgH,)2(H)CO and M(n -C,H,)2H2 (M-Nb, Ta) yields the monohydrides M(ti -C5Hs)H, uld irradiation of (ti -C.Hs)2V(CH,)2 results in formation of methane and ethame. The amount of ethaine formed is dependent on the solvent, concentration of substrate, time aind temperature.  [Pg.105]

Treatment of niobium or tantalum pentachloride with dimethylzinc in pentane gives golden-yellow crystals of the trimethyl derivatives Me3MCl2, where M = Nb or Ta. These complexes decompose at room temperature and are readily oxidized. The tantalum complex is less thermally stable than the niobium analogue [84], [Pg.240]

Studies related to the chendsby of die metal cartxm of this group continue to run at a low level That said, 1994 brou the preparation of the first zero-valent tantalum carbon in die form of Ta(CO)4( pe) The molecule exhibits diree v(CO) bands at 1963 cm (aj, m) 1893 cm (a, m) and 1880 cm (bj b2, vs) which would be expected for a ei -tetracarbonyl like this. Tantalum also figures in the first example of an (i7 -H2) carbonyl-containing compound in this groiq), namely [Cp2Ta(T7 -H2XC0)]BF4. [Pg.163]

The photoredox reactions of the cluster compounds [Nb5Clj 2] have been described. [Pg.67]

Suliiir reacts with Cp 2Nb(CO)CH2Si(CH3)3 to yield the carbonyl sulfide Cp 2 Nb (ii -COS)CH2Si(CH3)3 in an interesting reaction. A series of reactiviQr studies has been carried out on niobocene sulfide e.g. Cp2 NbBH4 reacts with S to give three products, two isomers of [Pg.407]

The niobium ketene-hydride complex (Cp 2Nb(H)(ii -C,0-0C CPh2)], Cp - n -CsH4SiMe3 reacts with nitriles or isonitriles to give isocyanate and the complex Cp 2NbH( C CPli2)]. Further work has been carried out on the chiral [Pg.408]


R. J. H. Clark and D. Brown, The Chemisty of Vanadium, Niobium and Tantalum, Pergamon Press, Ehnsford, N. Y., 1975. [Pg.30]

Table 22.2 Oxidation states and stereochemistries of compounds of vanadium, niobium and tantalum... Table 22.2 Oxidation states and stereochemistries of compounds of vanadium, niobium and tantalum...
The known halides of vanadium, niobium and tantalum, are listed in Table 22.6. These are illustrative of the trends within this group which have already been alluded to. Vanadium(V) is only represented at present by the fluoride, and even vanadium(IV) does not form the iodide, though all the halides of vanadium(III) and vanadium(II) are known. Niobium and tantalum, on the other hand, form all the halides in the high oxidation state, and are in fact unique (apart only from protactinium) in forming pentaiodides. However in the -t-4 state, tantalum fails to form a fluoride and neither metal produces a trifluoride. In still lower oxidation states, niobium and tantalum give a number of (frequently nonstoichiometric) cluster compounds which can be considered to involve fragments of the metal lattice. [Pg.988]

Hydrogen reduction has a major advantage in that the reaction generally takes place at lower temperature than the equivalent decomposition reaction. It is used extensively in the deposition of transition metals from their halides, particularly the metals of Groups Va, (vanadium, niobium, and tantalum) and Via (chromium, molybdenum, and tungsten). The halide reduction of Group IVa metals (titanium, zirconium, and hafnium) is more difficult because their halides are more stable. [Pg.70]

The 5th group metals a summary of their atomic and physical properties Vanadium, niobium and tantalum have only the bcc, W-type, structure no high-temperature or high-pressure polymorphs are known. [Pg.406]

Indicate the position of vanadium, niobium, and tantalum in Mendeleev s periodic table of the elements, the electron configurations and size of their atoms, and their oxidation states. [Pg.210]

What place do these metals occupy in the electrochemical series How do they react with acids and alkalies What compounds form when vanadium, niobium, and tantalum react with oxygen, the halogens, and sulphur ... [Pg.210]

The group IV B elements titanium, zirconium, and hafnium exhibit the normal isotope effect. Most of the data for the titanium-hydrogen system have been obtained at elevated temperatures. However, extrapolation of the available data (II, 13,31) to room temperature indicates a normal effect for hydrogen and deuterium. The group VB metals vanadium, niobium, and tantalum, on the other hand, exhibit inverse isotope effects indeed, these are the only pure metals that exhibit the inverse effect near room temperature. Extensive data have been reported for these systems. The P-C-T data obtained by Wiswall and Reilly (32) for vanadium hydrogen and deuterium clearly show a greater stability for... [Pg.353]

Nitrates and carbonates of vanadium, niobium, and tantalum have not been prepared. Niobium and tantalum salts of other weak acids, e.g. boric add, hydrocyanic add, phosphoric acid, are also unknown, and in the case of vanadium are not well defined. [Pg.5]

The pentoxides of vanadium, niobium, and tantalum react with hydrogen peroxide to produce per-acids of the general formula HR04. H20. These per-acids increase in stability with increase in atomic weight. Pertantalic acid is a white solid which can be heated to 100° C. without undergoing decomposition. The oxyfluorides of these metals also take up active oxygen to yield peroxyfluorides, which are much better defined in the case of niobium and tantalum than with vanadium. [Pg.7]


See other pages where Vanadium, Niobium and Tantalum is mentioned: [Pg.110]    [Pg.980]    [Pg.982]    [Pg.984]    [Pg.986]    [Pg.988]    [Pg.988]    [Pg.989]    [Pg.990]    [Pg.992]    [Pg.993]    [Pg.994]    [Pg.994]    [Pg.28]    [Pg.394]    [Pg.441]    [Pg.211]    [Pg.218]    [Pg.444]    [Pg.124]    [Pg.166]    [Pg.104]    [Pg.267]    [Pg.569]    [Pg.427]    [Pg.1]    [Pg.3]    [Pg.4]    [Pg.5]    [Pg.6]    [Pg.6]    [Pg.8]    [Pg.8]    [Pg.10]    [Pg.12]    [Pg.14]    [Pg.16]   


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Compounds of Vanadium, Niobium and Tantalum

Group 5 (Vanadium, Niobium and Tantalum)

Niobium and vanadium

Niobium-Tantalum

Related Compounds of Vanadium, Niobium, and Tantalum

The sulphides of vanadium, niobium, and tantalum

Vanadium and

Vanadium niobium

Vanadium tantalum

Vanadium, Niobium and Tantalum Carbides

Vanadium, Niobium, Tantalum, and Protactinium

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