Rhenium(VII) Oxo and Imido Complexes:  Synthesis, Structures, and Applications

Romão, Carlos C.; Kühn, Fritz E.; Herrmann, Wolfgang A.

doi:10.1021/cr9703212

Cited by 521 publications

(266 citation statements)

References 283 publications

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“…[1,2,3] For manganese, the high electron affinity and oxidation potential of its heptavalent complexes make these species the catalysts of choice for oxidation of organic compounds.…”

mentioning

confidence: 99%

“…[3] Concerning technetium, its coordination chemistry has mainly been driven by radiopharmaceutical applications. Pentavalent and trivalent Tc complexes have been the most studied while heptavalent coordination complexes are still rare.…”

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confidence: 99%

“…The extended x-ray absorption fine structure (EXAFS) spectrum was k 3 Figure S2 and S3 in supporting information) exhibit respectively a significant peak around 3.2 Å due to Tc Tc scattering and around 2.8 Å due to Tc S scattering.…”

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confidence: 99%

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Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies

et al. 2010

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Summary. The speciation of Tc(VII) in 12 M sulfuric acid was studied by NMR, UVvisible and XAFS spectroscopy, experimental results were supported by DFT calculation and were in agreement with the formation of TcO 3 OH(H 2 O) 2 .Heptavalent transition metal complexes of group VII with the d 0 electronic configuration are often used in catalysis and biomedical applications. [1,2,3] For manganese, the high electron affinity and oxidation potential of its heptavalent complexes make these species the catalysts of choice for oxidation of organic compounds.[4] The chemistry of Re(VII) complexes has been extensively studied, and species with the ReO 3 + core (e.g., CH 3 ReO 3 ) have been reported to be efficient catalysts. [3] Concerning technetium, its coordination chemistry has mainly been driven by radiopharmaceutical applications. Pentavalent and trivalent Tc complexes have been the most studied while heptavalent coordination complexes are still rare. [5] Permetallates with the tetrahedral geometry are the most common heptavalent species and are stable in aqueous media over a large range of pH and electrochemical potential. [6] In concentrated acid, permetallates are generally unstable and reduction, dimerisation, dehydration or complexation can occur. [7,8,9,10] The reaction of pertechnetate in water with strong acid leads to dehydration and various complexes with TcO 3 + core have been synthesized. [11] In theses synthetic reactions, it is assumed that the anhydrous Tc 2 O 7 is formed as an intermediate product. [11] Sulfuric acid is widely used in industrial applications; it is also a solvent of choice for dehydration process. [12-13] Speciation of Mn(VII) in H 2 SO 4 has been documented; manganese heptoxide is formed after dissolution of KMnO 4 and the MnO 3 + cation has been reported. [14,15,16]. For technetium and rhenium, speciation data are still sparse, the HReO 2 (SO 4 ) 2 .3H 2 O complex has been mentioned while technetium heptoxide has been proposed but no structural nor speciation data were provided. [17][18] In the present work, the speciation of technetium complexes after dissolution of KTcO 4 in sulfuric acid has been performed. The molecular structure and spectroscopic properties of the complexes were studied by UV-visible, X-ray absorption fine structure (XAFS) and NMR spectroscopy and density functional theory (DFT) techniques.Potassium pertechnetate (~ 30 mg) was placed in glass vials, and 1 M, 6 M, 12 M sulfuric acid (5 mL) was added with a glass pipette. After dissolution of the salt, a yellow color is observed in 12 M while for 1 M and 6 M, the solution remains clear. UV-visible spectroscopy measurements in 1 M and 6 M show the presence of TcO 4 -while in 12 M, the spectrum of the yellow solution differs from that of the pertechenate (vide supra). The conditions of formation of the yellow species were investigated by NMR spectroscopy. Technetium samples were prepared in H 2 SO 4 (from 3 M to 18 M) and 99 The 99 Tc NMR data were fit by allowing the pK a s and the chemical shifts of the unprot...

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“…[1,2,3] For manganese, the high electron affinity and oxidation potential of its heptavalent complexes make these species the catalysts of choice for oxidation of organic compounds.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies

et al. 2010

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“…Re is known to be an oxophilic element with various valences, 180,181 but the high sublimation propensity of Re 2 O 7 prevents development of Re catalysts for oxidation. 182,183 However, supported ReO x compounds on oxide surfaces have been reported to be different from those on unsupported ReO x compounds.…”

Section: Tadamentioning

confidence: 99%

Surface-Mediated Design and Catalytic Properties of Active Metal Complexes for Advanced Catalysis Creation

Tada¹

2010

Bulletin of the Chemical Society of Japan

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Molecular-scale design of catalytically active structures at oxide surfaces is highlighted, focusing on our recent challenges for selective heterogeneous catalysis. We found novel structural transformations of supported metal complexes on oxide surfaces and achieved unique selective catalysis for various chemical syntheses. In this account, the advanced design of supported metal-complex catalysts on oxide surfaces and the in situ characterization of their structural kinetics, which means kinetics of structural changes of catalysts themselves, under catalyst-working conditions are reviewed. Surface-Mediated Design of Catalytically ActiveStructures for Selective Catalysis 1.1 Introduction: Metal-Complex Attaching on Oxide Surfaces. Heterogeneous solid catalysts have been widely utilized for the industrial production of many synthetic chemicals. The advantages of heterogeneous catalysts are not only the separation of catalysts and products from reaction media but also their high durability and catalytic activities resulting from the unique structures of catalytically active sites at solid surfaces. Relationships among the metal structures, organized environment, and the catalytic properties of surface species tell us the nature of catalysis and new strategy for rational design of heterogeneous catalysts.Metal-complex attachment to oxide surfaces is a practical way to produce molecularly regulated structures of active metal species on oxide surfaces, and subsequent structural transformation in a controllable manner often provides unique regulated metal structures active for selective catalytic reactions. 116 There are several types of metal-complex attachment techniques: coordination of metal-complex precursors to immobilized ligands on organic polymers, 1721 coordination of metal-complex precursors to functional ligands bound to oxide surfaces, 2,4,2225 intercalation into clay materials, 26 ion exchange into porous materials such as zeolite and mesoporous silica, 27 and direct attachment of metal-complex precursor onto oxide surfaces. 3,6,11,28,29 The interfacial attachment between a metal complex and an oxide surface can produce unique metal coordination different from the original metal-complex precursor. For example, SiOH is reacted with a M(CH 3 ) complex and a M(OSi) complex is produced, releasing CH 4 . A chemical bond between a metal-complex precursor and a support surface modifies the reactivity of the supported metal complex, resulting in novel catalytic activity the precursor complex does not exhibit. 3,6,11,28,29 Traditional ion-exchange on zeolites and intercalation to clay materials are also typical ways to introduce metal species onto solid supports although the valences and types of metal precursors are restricted. 4 Direct reactions of metal-complex precursors and hydroxy groups on oxide surfaces create novel metal-coordination structures, and many important factors for selective catalysis can be controlled at the interface, such as electronic properties and coordination sphere of the attached metal...

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“…Transition metal compounds such as metalloporphyrin [12], titanosilicates [13], methyltrioxorhenium [14], tungsten compounds [15][16][17][18], polyoxometalates [19,20], and manganese complexes [21] have been employed as a catalyst for H2O2-based epoxidation, either homogeneous or heterogeneous. Unfortunately, these systems have disadvantages, such as low efficiency of H2O2 utilization and low selectivity to epoxides (or low stereospecificity) [12][13][14][15][16][17][18][19][20], limited number of applicable olefins [21], and high reaction temperatures [15][16][17] complexes were reported to efficiently epoxidize aromatic or substituted alkenes with high yields using peroxycarboxylic acids at -80 ℃, where salen is N,N'-bis(salicylidene)ethylenediamine [23,24]. However, these catalysts are not effective in epoxidizing most terminal and trans-olefins [25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature and Reaction Time on the Synthesis of Butadiene Monoepoxide Using Iron Complex as an Efficient Catalyst

Zong¹,

Kharismadewi²,

Sup³

et al. 2012

Clean Technology

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at -10 ℃ with low catalyst loadings by using commercially available peracetic acid as an oxidant. The main aspect of our study is to investigate the effect of temperature (from -10 to -40 ℃) and time on the epoxidation reaction. The epoxidation reaction was fast and almost completed within 5 min at temperatures above -20 ℃, whereas it became slow at temperatures below -20 ℃. The yield of butadiene monoepoxide (BMO)increased with increasing the reaction time. Generally, when the more butadiene was used, the higher yield was obtained. The highest yield of BMO was 90%.

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Rhenium(VII) Oxo and Imido Complexes: Synthesis, Structures, and Applications

Cited by 521 publications

References 283 publications

Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies

Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies

Surface-Mediated Design and Catalytic Properties of Active Metal Complexes for Advanced Catalysis Creation

Effect of Temperature and Reaction Time on the Synthesis of Butadiene Monoepoxide Using Iron Complex as an Efficient Catalyst

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