Oxo-molybdenum and oxo-tungsten complexes of Schiff bases relevant to molybdoenzymes

Lyashenko, G. S.; Saischek, Gerald; Judmaier, Martina E.; Volpe, Manuel; Baumgartner, Judith; Belaj, Ferdinand; Jancik, Vojtech; Herbst‐Irmer, Regine; Mösch‐Zanetti, Nadia C.

doi:10.1039/b820629e

Cited by 52 publications

(64 citation statements)

References 55 publications

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“…Molybdenum complexes are well known as active centers of several enzymes such as oxotransferases [1][2][3][4]. Some molybdates show antiviral, antitumoral or antibiotic activity [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that mononuclear peroxo and mono-oxo bridged dinuclear molybdenum complexes are active catalysts for the epoxidation of olefins and nonfunctionalized olefins with t-butylhydroperoxide TBHP as oxygen donor [8,[13][14][15]. The epoxidation of olefins catalyzed by a large family of complexes with MoO 2 X 2 (N-N) 2 or MoO 2 X 2 (N-O) 2 formula where N-N or N-O are bidenate ligands and X = Cl, Br or Me has been previously reported [10,11,15,16]. All these catalysts show high activity and selectivity.…”

Section: Introductionmentioning

confidence: 99%

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Molybdenum Complexes as Catalysts for the Oxidation of Cycloalkanes with Molecular Oxygen

et al. 2016

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A group of new polymolybdates was synthesized and tested in the catalytic oxidation of cycloalkanes. Investigated compounds exhibit broad structural diversity including polymolybdates with isolated anionic clusters (0-dim), polymeric anions (1-dim), Mo-O layers (2-dim) as well as hexagonal and orthorhombic molybdenum oxides (3-dim). All studied molybdenum complexes were found to be active in the reaction conditions yielding ketones and alcohols as main products. In the case of layered compounds (2-dim), dicarboxylic acid was detected in the mixture of reaction products. The structure of investigated molybdenum compounds was shown to have influence on yields and selectivities of the investigated reactions. Anionic layers separation (in 2-dim materials) as well as type and charge of organic cations present in the compounds are prime examples of structural factors influencing the oxidation reactions efficiencies. On the basis of obtained results and literature reports a mechanism for the oxidation of cycloalkanes by polymolybdates has been proposed. Graphical Abstract

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molybdenum Complexes as Catalysts for the Oxidation of Cycloalkanes with Molecular Oxygen

et al. 2016

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“…In NOWHUC, the intra-(1.892) and inter-"monomer" (1.955 Å) Li-O distances are most similar to those in 2b. In the structure of a 2,6-xylyl ketoiminate a structure very similar to that in 2b is found (refcode: SEKVIP) [21]. In place of the two THF molecules, two neutral ligand molecules are coordinated to lithium ions via the carbonyl oxygen donors.…”

Section: Transoid LI 2 O 2 Clustersmentioning

confidence: 78%

“…A fluorinated β-ketoiminate with a pendent Me 2 N'CH 2 CH 2 has been structurally characterised (refcode: XUZWOE) as a cisoid Li 2 O 2 dimer with the N' donors acting as an internal Lewis base [19], while a mixed copper-lithium ladder cluster was obtained from lithiated 1a and copper(I) chloride in toluene in which an oxygen from the copper chelate acts as "L" [20]. A similar Li 2 O 2 cluster (refcode: SEKVIK) of a close analogue of ligand 1b (2,6-xylyl rather than Mes group) has two neutral ligands filling the coordination sphere of the lithium ions [21]. An iron(II) triflate complex derived from 1a (refcode: ISEXUA) has recently been structurally characterised [22].…”

Section: Introductionmentioning

confidence: 99%

Backbone-Substituted β-Ketoimines and Ketoiminate Clusters: Transoid Li2O2 Squares and D2-Symmetric Li4O4 Cubanes. Synthesis, Crystallography and DFT Calculations

Gietz

Boeré

2017

Inorganics

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Abstract:The preparation and crystal structures of four β-ketoimines with bulky aryl nitrogen substituents (2,6-diisopropylphenyl and 2,4,6-trimethylphenyl) and varying degrees of backbone methyl substitution are reported. Backbone substitution "pinches" the chelate ring. Deprotonation with n-butyllithium leads to dimeric Li 2 O 2 clusters, as primary laddered units, with an open transoid geometry as shown by crystal structures of three examples. The coordination sphere of each lithium is completed by one tetrahydrofuran ligand. NMR spectra undertaken in either C 6 D 6 or 1:1 C 6 D 6 /d 8 -THF show free THF in solution and the chemical shifts of ligand methyl groups experience significant ring-shielding which can only occur from aryl rings on adjacent ligands. Both features point to conversion to higher-order aggregates when the THF concentration is reduced. Recrystallization of the materials from hydrocarbon solutions results in secondary laddering as tetrameric Li 4 O 4 clusters with a cuboidal core, three examples of which have been crystallographically characterised. These clusters are relatively insoluble and melt up to 250 • C; a consideration of the solid-state structures indicates that the clusters with 2,6-diisopropylphenyl substituents form very uniform ball-like molecular structures that will only be weakly solvated.

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“…For a comparison, octahedral Schiff base (SB) complexes, [MoO 2 (SB) 2 ] (Figure 5b), which coordinated to molybdenum via nitrogen and oxygen donors, were synthesised. [18] Although replacing one nitrogen by one oxygen donor in the used ligand systems certainly diminishes the comparability of the two types of complexes, both were actually carefully designed. In the two different ligands, formally one of the donor atoms is involved in a double bond to the three-carbon backbone of the respective ligand, whereas the other is connected to it via a single bond, and the double bonds that are present are mobile, allowing different mesomeric species of the respective ligand to form.…”

Section: Active-site Geometrymentioning

confidence: 99%

Molybdenum and Tungsten Oxidoreductase Models

Schulzke

2011

Eur J Inorg Chem

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This microreview gives an overview about advances in bioinorganic model chemistry for molybdenum‐ and tungsten‐dependent oxidoreductases with respect to specific aspects of the evolution, structure or function of distinct active‐site properties. The approaches to evaluate catalytic properties fine‐tuned by the ligand sphere, interpret and assign enzyme spectra and to understand why two different metals are used for the same task but in distinct habitats and respective evolutionary aspects are discussed on the basis of exemplary case studies. This short review provides a personal perspective and appreciation of the complex problems associated with the respective foremost synthetic and analytical model chemistry and their solutions partly accompanied and supported by theoretical results.

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Oxo-molybdenum and oxo-tungsten complexes of Schiff bases relevant to molybdoenzymes

Cited by 52 publications

References 55 publications

Molybdenum Complexes as Catalysts for the Oxidation of Cycloalkanes with Molecular Oxygen

Molybdenum Complexes as Catalysts for the Oxidation of Cycloalkanes with Molecular Oxygen

Backbone-Substituted β-Ketoimines and Ketoiminate Clusters: Transoid Li2O2 Squares and D2-Symmetric Li4O4 Cubanes. Synthesis, Crystallography and DFT Calculations

Molybdenum and Tungsten Oxidoreductase Models

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