cis-Dioxo- and trioxo-complexes

Griffith, William P.; Wickins, T. D.

doi:10.1039/j19680000400

Cited by 133 publications

(83 citation statements)

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“…4 . A sharp stretching Raman mode at 866 cm 1 from n O-O has been observed as reported 26 to appear around this area together with a strong peak at 614 cm 1 of n Nb-O 2 which also appeared in the spectrum. The TG profile Fig.…”

Section: Characterizationmentioning

confidence: 77%

Water Soluble Na[Nb(O2)3]•2H2O as a New Molecular Precursor for Synthesis of Sodium Niobate

Dey

Petrykin

Sasaki

et al. 2007

J. Ceram. Soc. Japan

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Section: Characterizationmentioning

confidence: 77%

Water Soluble Na[Nb(O2)3]•2H2O as a New Molecular Precursor for Synthesis of Sodium Niobate

Dey

Petrykin

Sasaki

et al. 2007

J. Ceram. Soc. Japan

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“…[11] Here p bonding is thought to contribute to the small O-Mo-O bond angles (around 101 ± 1058). [8,11] Small O-M-O angles are also found for chromyl complexes, CrO 2 X 2 , and for a considerable number of related compounds. We will show here, by analyzing the results of density functional calculations, how these apparently contradictive views on the relation between p bonding and bond angles may be reconciled.…”

Section: Introductionmentioning

confidence: 81%

“…These orbitals and their influence on bonding have been discussed by various workers. [8,11] However, let us consider in somewhat more detail which changes in p bonding may be expected to happen upon bending such an MX 2 molecule. Starting from the linear structure (bending angle a 1808), we first loose any in-plane p bonding from the d yz (b 2 ) orbital, as the overlap with the ligand orbitals decreases rapidly (at the same time this d yz orbital starts to be involved more efficiently in s bonding, cf.…”

Section: Methodsmentioning

confidence: 99%

“…This is attributed largely to a better stabilization of the octahedron relative to the trigonal prism by p bonding. ªmolybdenyl fragmentº, MoO 2 2 , which is present in many Mo VI dioxo complexes [8,9,10] but has also recently been considered computationally as an isolated species. [11] Here p bonding is thought to contribute to the small O-Mo-O bond angles (around 101 ± 1058).…”

Section: Introductionmentioning

confidence: 99%

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On the Relation between π Bonding, Electronegativity, and Bond Angles in High-Valent Transition Metal Complexes

Kaupp

1999

Chem. Eur. J.

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Ligand-to-metal p bonding is important for the understanding of bond angles in d 0 transition metal complexes. This is demonstrated by density functional calculations on a number of model complexes, combined with natural bond orbital and natural localized molecular orbital analyses. Analyses of the simple model systems ScF 2 and ZrO 2 indicate a complicated dependence of p bonding on bond angle. In particular, in-plane p bonding exhibits a nonuniform dependence, whereas outof-plane p bonding shows a more regular behavior. This may be understood from the nodal properties of the relevant metal d orbitals. The net p bonding behavior then depends sensitively on the donor properties of the ligands. While p bonding appears to favor the bent equilibrium structure for the ªstrong pdonor caseº ZrO 2 , it is more efficient at a linear structure for the ªweak pdonor caseº ScF 2. Similar considerations come into play for more complicated species, exemplified by MX 2 Y 2 model complexes. Thus, the ªinverse Bents rule structuresº of TiCl 2 (CH 3 ) 2 and TiCl 2 H 2 are related to the improved in-plane p(Ti ± Cl) bonding at larger ClTi-Cl angles. In contrast, for CrO 2 F 2 or MoO 2 F 2 , the angular dependences of the strong in-plane and out-of-plane components of p(M ± O) bonding compensate each other partially, and the O-M-O angles appear to be dominated by the s-bonding framework. When introducing a strong s-bonding ancillary ligand, as in CrO 2 H 2 , the net p bonding does again seem to favor larger angles. Electronegativity effects on bond angles have been probed by studying heteroleptic complexes without significant p bonding. ªInverse structuresº are found for complexes like TiH 2 (CF 3 ) 2 or Ti-(SiH 3 ) 2 (CH 3 ) 2 , that is the smaller angles are those between the less electronegative ligands. Hybridization analyses indicate less d character for these bonds. The interpretation is complicated by the fact that even the structure for the silicon analogon of the latter complex violates Bents rule. In general, Bents rule appears to be less useful for d 0 transition metal complexes than for main group compounds, in part due to the much larger importance of p bonding for the former.

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“…In the infrared spectra two characteristic absorptions at 862 and 873 cm Ϫ1 (1) and 825 and 875 cm Ϫ1 (2) are assigned to the symmetric and the antisymmetric stretches of the cis-VO 2 moiety. 7 A strong absorption at 1668 (1) and 1623 cm Ϫ1 (2) is attributed to the asymmetric vibration of the carboxylato function of the ligand. In the 1 H NMR spectra of both compounds the expected four signals of the tetrabutylammonium cation are observed in the aliphatic region as well as the expected signals of the ligands in the aromatic region: three for the pca units in 1 and four for the ana units in 2.…”

Section: Reaction Of [Nbu 4 ][Vo 3 ] With Pyrazine-2-carboxylic Acid mentioning

confidence: 99%

Oxidative functionalisation of alkanes: synthesis, molecular structure and catalytic implications of anionic vanadium(V) oxo and peroxo complexes containing bidentate N,O ligands †

Süß‐Fink¹,

Stanislas²,

Shul’pin³

et al. 1999

J. Chem. Soc., Dalton Trans.

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A mixture of [NBu 4 ][VO 3 ] and pyrazine-2-carboxylic acid (Hpca) in acetonitrile catalysed smoothly the reaction of alkanes RH (R = CH 3 or C 6 H 11 ) with molecular oxygen (from air) and hydrogen peroxide to give the corresponding alkyl hydroperoxide ROOH as the primary product. The use of methane as an alternative feedstock for valuable C 1 oxygenates is of great scientific and practical interest due to the considerable reserves of natural gas, although methane is the most inert organic compound.1,2 Previously we have shown that methane and other saturated hydrocarbons are readily oxidised by molecular oxygen (in air) and hydrogen peroxide in the presence of a catalytic system composed of vanadate() and pyrazine-2-carboxylic acid; the reaction takes place either in acetonitrile 3 or in water 4 as solvent. If the reaction is performed under mild conditions (<50 ЊC) the corresponding alkyl hydroperoxides, formed as primary products, are obtained in good selectivities as major products. At higher temperatures the reaction gives mainly alcohols and ketones. 3,4In order to elucidate the function of the catalyst mixture in this remarkable catalytic reaction we decided to study systematically (1) the variation of the co-catalyst and its influence on the catalytic activity, (2) the co-ordination chemistry of vanadate() with pyrazine-2-carboxylic acid and related cocatalysts, and (3) the reactivity of the vanadate() complex obtained towards hydrogen peroxide. In this paper we report the synthesis and X-ray crystallographic characterisation of the oxo complexes [VO 2 L 2 ] Ϫ [HL = pyrazine-2-carboxylic acid (Hpna) or anthranilic acid (Hana)] and of the peroxo complex [VO(O 2 )(pca) 2 ] Ϫ . Their implication in the catalytic process is also discussed.

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cis-Dioxo- and trioxo-complexes

Cited by 133 publications

References 0 publications

Water Soluble Na[Nb(O<sub>2</sub>)<sub>3</sub>]•2H<sub>2</sub>O as a New Molecular Precursor for Synthesis of Sodium Niobate

Water Soluble Na[Nb(O<sub>2</sub>)<sub>3</sub>]•2H<sub>2</sub>O as a New Molecular Precursor for Synthesis of Sodium Niobate

On the Relation between π Bonding, Electronegativity, and Bond Angles in High-Valent Transition Metal Complexes

Oxidative functionalisation of alkanes: synthesis, molecular structure and catalytic implications of anionic vanadium(V) oxo and peroxo complexes containing bidentate N,O ligands †

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cis-Dioxo- and trioxo-complexes

Cited by 133 publications

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Water Soluble Na[Nb(O<sub>2</sub>)<sub>3</sub>]&bull;2H<sub>2</sub>O as a New Molecular Precursor for Synthesis of Sodium Niobate

Water Soluble Na[Nb(O<sub>2</sub>)<sub>3</sub>]&bull;2H<sub>2</sub>O as a New Molecular Precursor for Synthesis of Sodium Niobate

On the Relation between π Bonding, Electronegativity, and Bond Angles in High-Valent Transition Metal Complexes

Oxidative functionalisation of alkanes: synthesis, molecular structure and catalytic implications of anionic vanadium(V) oxo and peroxo complexes containing bidentate N,O ligands †

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Water Soluble Na[Nb(O<sub>2</sub>)<sub>3</sub>]•2H<sub>2</sub>O as a New Molecular Precursor for Synthesis of Sodium Niobate

Water Soluble Na[Nb(O<sub>2</sub>)<sub>3</sub>]•2H<sub>2</sub>O as a New Molecular Precursor for Synthesis of Sodium Niobate