Vanadium

Berno, Pietro; Gambarotta, Sandro; Richeson, Darrin S.

doi:10.1016/b978-008046519-7.00038-1

Cited by 9 publications

(7 citation statements)

References 350 publications

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“…This statement can be read in a comprehensive review on the organometallic chemistry of vanadium and is still valid today. [1] Even rarer, however, are those organovanadium(iii) derivatives in which a given alkyl or aryl group R is the only ligand coordinated to the metal and hence solely responsible for the stability of the complex species. These homoleptic s-organyl compounds [2] are of fundamental interest and should have the general formula [VR n ] (nÀ3)À , n being a small integer.…”

Section: Introductionmentioning

confidence: 99%

“…The hr Table 6 follow the sequence C 6 Cl 5 % NEt 2 > OCMe 3 > mes > SCMe 3 , and so it can be concluded that the V IV ÀC 6 Cl 5 bond is in the upper range of ionic character for such homoleptic species. The behaviour of the perchlorinated and partially chlorinated phenyl groups is, however, indistinguishable in these d 1 stoichiometry is unprecedented in organometallic chemistry. Compound 7 must be handled with great caution and kept at low temperature (À30 8C) because it is prone to explode by percussion and easily undergoes thermal decomposition.…”

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confidence: 96%

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New Homoleptic Organometallic Derivatives of Vanadium(III) and Vanadium(IV): Synthesis, Characterization, and Study of Their Electrochemical Behaviour

Alonso

Forniés

García‐Monforte

et al. 2005

Chemistry A European J

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The arylation of [VCl3(thf)3] with LiR(Cl), where R(Cl) is a polychlorinated phenyl group [C6Cl5, 2,4,6-trichlorophenyl(tcp), or 2,6-dichlorophenyl (dcp)] gives four-coordinate, homoleptic organovanadium(III) derivatives with the formula [Li(thf)(4)][V(III)(R(Cl))(4)] (R(Cl) = C(6)Cl(5) (1), tcp (2), dcp (3)). The anion [V(III)(C6Cl5)4]- has an almost tetrahedral geometry, as observed in the solid-state structure of [NBu4][V(C6Cl5)4] (1') (X-ray diffraction). Compounds 1-3 are electrochemically related to the neutral organovanadium(IV) species [V(IV)(R(Cl))4] (R(Cl) = C6Cl5 (4), tcp (5), dcp (6)). The redox potentials of the V(IV)/V(III) semisystems in CH2Cl2 decrease with decreasing chlorination of the phenyl ring (E(1/2) = 0.84 (4/1), 0.42 (5/2), 0.25 V (6/3)). All the [V(IV)(R(Cl))4] derivatives involved in these redox couples could also be prepared and isolated by chemical methods. The arylation of [VCl(3)(thf)(3)] with LiC6F5 also gives a homoleptic organovanadium(III) compound, but with a different stoichiometry: [NBu4]2[V(III)(C6F5)5] (7). In this five-coordinate species, the C6F5 groups define a trigonal bipyramidal environment for the vanadium atom (X-ray diffraction). EPR spectra for the new organovanadium compounds 1-6 are also given and analysed in terms of an elongated tetrahedral structure with C(2v) local symmetry. It is suggested that the R(Cl) groups exert a protective effect towards the vanadium centre.

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 96%

New Homoleptic Organometallic Derivatives of Vanadium(III) and Vanadium(IV): Synthesis, Characterization, and Study of Their Electrochemical Behaviour

Alonso

Forniés

García‐Monforte

et al. 2005

Chemistry A European J

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“…The second point of interest concerns the oxidation state of the vanadium center during the catalytic cycle. The +3 oxidation state of vanadium is a fairly stable one, and a few examples of stable homoleptic alkyl derivatives have been reported in the literature . On the other hand, the aluminum alkyl cocatalyst certainly has the sufficient reducing strength to lower the oxidation state of vanadium to the +2 state 11a.…”

Section: Introductionmentioning

confidence: 99%

Vanadium-Catalyzed Ethylene−Propylene Copolymerization: The Question of the Metal Oxidation State in Ziegler−Natta Polymerization Promoted by (β-diketonate)₃V

Ma¹,

Reardon²,

Gambarotta³

et al. 1999

Organometallics

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Four different (β-diketonate)3V complexes [β-diketonate = 2,4-pentanedione (acac), 2-acetylcyclohexanone (Cy-acac), 2,2,6,6-tetramethyl-3,5-heptanedione (t-Bu-acac), and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (F-acac)] have been prepared and tested as catalysts for propylene−ethylene copolymerization with the aim of gaining insights into the structure of the active species. Data on polymer composition and catalyst activity indicate that one of the roles of the Al cocatalyst is to trigger a major ligand scrambling around the transition metal. Attempts to isolate the catalytically active species afforded a compound formulated as {[(β-diketonate)AlCl2][VCl2][(β-diketonate)2AlCl]}. This species, which displayed only a minor catalytic activity, arises from a parasite process (catalyst deactivation). The formulation was supported by chemical degradation experiments with THF, which afforded a mixture of [V2Cl3(THF)6][AlCl4] and [(acac)2Al(THF)2][Al Cl4] (5). Two unprecedented V(II) complexes (R-acac)2V(TMEDA) [R = H(7a), Cy(7b), t-Bu (7c)] have been prepared and reacted with halocarbons to model the reactivation process. The results indicated that the primary role of reactivating substances, commonly employed in the industrial processes, is to reoxidize V(II) to the trivalent state. The reaction formed the catalyst precursor (R-acac)2VCl(TMEDA), which was characterized on the basis of analytical and spectroscopic data. In agreement with this proposal, a trapping experiment carried out with ZnCl2 or oxidation with CuCl allowed the isolation and characterization of (t-Bu-acac)2V(TMEDA)][X] [X = ZnCl4 - (8), CuCl2 - (9)]. The structures of 5, 7a, 8, and 9 have been elucidated by X-ray diffraction. Crystal data are as follows. 5: triclinic space group P1̄, a = 8.916(3) Å, b = 9.802(3) Å, c = 15.390(5) Å, α = 88.156(4)°, β = 86.041(4)°, γ = 82.710(4)°, Z = 2. 7a: triclinic space group P1̄, a = 7.896(1) Å, b = 10.032(2) Å, c = 13.134(2) Å, α = 75.265(2)°, β = 88.520(2)°, γ = 71.445(2)°, Z = 2. 8: orthorhombic space group Pbcn, a = 18.723(7) Å, b = 19.675(7) Å, c = 18.836(7) Å, Z = 4. 9: monoclinic space group C2/c, a = 13.676(5) Å, b = 19.521(3) Å, c = 13.206(3) Å, β = 98.47(3)°, Z = 4.

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“…The synthesis and structure of [(Me 3 Si) 2 N] 2 VCl(N 2 CPh 2 ), formed in what may also be viewed as an oxidation reaction, is also presented. Lastly, given the well-established ease of interconversion between Cp 2 V, Cp 2 VX, and Cp 2 VX 2 species, illustrative comparisons will be made between the chemistry of {Cp 2 V} versus {[(Me 3 Si) 2 N] 2 V} systems.…”

Section: Introductionmentioning

confidence: 99%

Oxidation Reactions of [(Me₃Si)₂N]₂VX(THF) (X = Cl, Me, Ph) with CuCl, PhCH(O)CH₂, and Ph₂CN₂ and the Syntheses and Structures of the Vanadium(III) Anions {[(Me₃Si)₂N]₂VX₂}^- (X = Cl, Me)

Gerlach

Arnold

1997

Organometallics

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One-electron oxidation of [(Me3Si)2N]2VX(THF) (X = Cl, Me, Ph) with CuCl afforded the V(IV), d1 species [(Me3Si)2N]2VCl(X) in moderate yields after crystallization from acetonitrile. [(Me3Si)2N]2VCl2 has been characterized crystallographically. The methyl and phenyl derivatives were conveniently synthesized in one step from [(Me3Si)2N]2VCl(THF) by first reacting first with LiMe or MgPh2, prior to treatment with CuCl. Reaction of [(Me3Si)2N]2VCl(THF) with dilithioacetylide in the presence of tetramethylethylenediamine (TMEDA) proceeded with redistribution of the Cl ligands, as the anionic V(III) compound [Li(TMEDA)2]{[(Me3Si)2N]2VCl2} was obtained in 44% yield as purple crystals. The analogous dimethyl anion [Li(TMEDA)2]{[(Me3Si)2N]2VMe2} was synthesized in 66% yield as deep-blue, highly air-sensitive crystals on treatment of [(Me3Si)2N]2VCl(THF) with 2 equiv of LiMe in the presence of TMEDA. X-ray crystallography showed that both salts crystallized as well-separated cations and anions. The reaction between styrene oxide and [(Me3Si)2N]2VMe(THF) proceeded stepwise, first yielding the μ-O intermediate {[(Me3Si)2N]2VMe}2(μ-O) and then the V(V) terminal oxo [(Me3Si)2N]2V(O)(Me). Styrene oxide also oxidized [(Me3Si)2N]2VPh(THF) to [(Me3Si)2N]2V(O)(Ph), however, in this case the putative μ-O intermediate could not be isolated as a stable material. Diphenyldiazomethane was reduced by two electrons to an alkylidenehydrazido(2-) on displacing THF from [(Me3Si)2N]2VCl(THF) to form the V(V) complex [(Me3Si)2N]2V(Cl)(N2CPh2). A crystal structure showed the diazoalkane to be coordinated in a doubly-bent fashion.

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Vanadium

Cited by 9 publications

References 350 publications

New Homoleptic Organometallic Derivatives of Vanadium(III) and Vanadium(IV): Synthesis, Characterization, and Study of Their Electrochemical Behaviour

New Homoleptic Organometallic Derivatives of Vanadium(III) and Vanadium(IV): Synthesis, Characterization, and Study of Their Electrochemical Behaviour

Vanadium-Catalyzed Ethylene−Propylene Copolymerization: The Question of the Metal Oxidation State in Ziegler−Natta Polymerization Promoted by (β-diketonate)₃V

Oxidation Reactions of [(Me₃Si)₂N]₂VX(THF) (X = Cl, Me, Ph) with CuCl, PhCH(O)CH₂, and Ph₂CN₂ and the Syntheses and Structures of the Vanadium(III) Anions {[(Me₃Si)₂N]₂VX₂}^- (X = Cl, Me)

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Vanadium

Cited by 9 publications

References 350 publications

New Homoleptic Organometallic Derivatives of Vanadium(III) and Vanadium(IV): Synthesis, Characterization, and Study of Their Electrochemical Behaviour

New Homoleptic Organometallic Derivatives of Vanadium(III) and Vanadium(IV): Synthesis, Characterization, and Study of Their Electrochemical Behaviour

Vanadium-Catalyzed Ethylene−Propylene Copolymerization: The Question of the Metal Oxidation State in Ziegler−Natta Polymerization Promoted by (β-diketonate)3V

Oxidation Reactions of [(Me3Si)2N]2VX(THF) (X = Cl, Me, Ph) with CuCl, PhCH(O)CH2, and Ph2CN2 and the Syntheses and Structures of the Vanadium(III) Anions {[(Me3Si)2N]2VX2}- (X = Cl, Me)

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Vanadium-Catalyzed Ethylene−Propylene Copolymerization: The Question of the Metal Oxidation State in Ziegler−Natta Polymerization Promoted by (β-diketonate)₃V

Oxidation Reactions of [(Me₃Si)₂N]₂VX(THF) (X = Cl, Me, Ph) with CuCl, PhCH(O)CH₂, and Ph₂CN₂ and the Syntheses and Structures of the Vanadium(III) Anions {[(Me₃Si)₂N]₂VX₂}^- (X = Cl, Me)