Rhenium Oxide Research Articles

Oxidations catalysed by rhenium(V) oxides 2. Clean sulfide oxidation by urea-hydrogen peroxide

Three rhenium(V) oxo phosphine complexes and methyltrioxorhenium have been used as catalysts for oxidation of sulfides to sulfoxides with urea-hydrogen peroxide as oxidant in acetonitrile; partial enantioselective oxidation of methylphenyl sulfide was observed with methyltrioxorhenium in the presence of a (+)-camphor derived pyrazine carboxylic acid.

ChemInform Abstract: Highly Diastereoselective Cyclizations of Bishomoallylic Tertiary Alcohols Promoted by Rhenium(VII) Oxide. Critical Steric versus Chelation Effects in Alkoxyrhenium Intermediates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Tandem Oxidative Cyclization with Rhenium Oxide. Total Synthesis of 17,18‐bisepi‐Goniocin.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ligand exchange reactions of ReCl 4(PPh 3) 2 with tridentate diacidic ligands with the donor set ONO(S). Molecular structures of the resulting oxo-rhenium(V) complexes

Ligand exchange reactions of ReCl 4(PPh 3) 2 with tridentate diacidic ligands with the donor set ONO(S) were studied. The reaction course was cleared up by mass spectrometric and X-ray structural analysis of intermediate and final products. The rhenium (IV chelates formed first react further to give oxo-rhenium(V) chelates via aerial oxidation. To clarify the structural properties of these rhenium(V) chelates, X-ray analyses were carried out. The crystal structures were determined for salicylaldehyde thiobenzoylhydrazonato (2−) salicylaldehyde thiobenzoylhydrazonato oxo-rhenium(V) ( 1) C 28H 21N 4O 3Re: monoclinic P2 1/c, a=9.9183(13), b=12.721(2), c=20.802(3) A ̊ , β = 96.416(13)°, Z = 4, R 1 = 0.0513; benzoylacetone thiobenzoylhydrazonato (2−) benzoylacetone thiobenzoylhydrazonato oxo-rhenium(V) ( 2) C 34H 29N 4S 2Re: triclinic P 1, a = 10.811(4), b = 11.364(9), c = 14.878(16) A ̊ , α = 67.56(4), β = 71.54(3) , γ = 79.50(3)°, Z = 2, R 1 = 0.0354. Benzoylacetonato-dichloro-triphenylphosphane-oxo-rhenium(V) ( 3b) is characterized as a decomposition product resulting from oxidation of rhenium(IV) to oxo-rhenium(V) and hydrolysis of the ligand benzoylacetone benzoylhydrazone. Crystal data for 3b. C 28H 24O 3PCl 2Re: monoclinic P2 1/c, a = 15.904(2), b = 11.021(5), c = 17.227(2) A ̊ , β = 115.476(11)°, Z=4, R 1 = 0.0394 .

Zum Chemischen Transport von Rhenium und Rheniumoxiden/On the Chemical Transport of Rhenium and Rhenium Oxides

Abstract Synthesis and single crystal growth by chemical transport reactions of rhenium and rhenium oxides is reported. Several transport agents like the mercury halides HgCl2, HgBr2, HgI2, tellurium tetrachloride and iodine have been employed the transport of the rhenium compounds. Mass spectrometric experiments gave informations about the composition of the gas phase. The transport reactions were traced by calculations based on the knowledge of the gas phase species and their thermodynamical data.

Highly Diastereoselective Cyclizations of Bishomoallylic Tertiary Alcohols Promoted by Rhenium(VII) Oxide. Critical Steric versus Chelation Effects in Alkoxyrhenium Intermediates

Highly Diastereoselective Cyclizations of Bishomoallylic Tertiary Alcohols Promoted by Rhenium(VII) Oxide. Critical Steric versus Chelation Effects in Alkoxyrhenium Intermediates

Preparation and reactions of rhenium(VII) trioxo hydrogendiolato complexes and rhenium(VI) oxo bis(diolato) complexes

The compound Re2O7, Re2O7·2H2O or [ReO3(OSiMe3)] reacted with H2diol to form complexes having the general formula [ReO3(Hdiol)] where H2diol = 2,3-dimethylbutane-2,3-diol (H2pin) or 1,1′-bicyclohexane-1,1′-diol (H2bicy). In the case of H2pin the complex [ReO3(Hpin)]·H2pin is formed initially in the reaction of rhenium(VII) oxides with an excess of pinacol. The hydrogen bonded free pinacol molecule can be removed by sublimation. The monomethyl derivative of pinacol, HMepin, reacts in a similar way to form the complex [ReO3(Mepin)]. In the rhenium(VII) compounds the Re atom has a distorted trigonal bipyramidal co-ordination geometry. Pale yellow solutions of [ReO3(Hdiol)] in CH2Cl2 slowly become orange and red crystals having the formula [ReO(diol)2] may be isolated. The reaction of rhenium(VII) oxides with H2diol and PPh3 in the presence of drying agents in CH2Cl2 produced the same compounds in high yield. The crystal structures of the rhenium(VI) complexes reveal that the rhenium(VI) cations have square pyramidal co-ordination geometries. The rhenium(VI) oxo bis(diolato) complexes are thermally stable and do not readily undergo oxidation in dry air.

Study of the electronic structure of rhenium and tungsten oxides on the O K-edge

Oxygen K-edge x-ray absorption spectra were studied on the electrochromic amorphous thin film a-WO3 in the comparison with crystalline oxides having variable electronic (d0, d1, d2) and atomic structure: monoclinic m-WO3 (insulator - d0), cubic Na0.6WO3 (metal - d1), cubic ReO3 (metal - d1), layered-type hexagonal h-WO3, WO3H2O and with intercalated HxReO3 (metal - d2), HxWO3 oxides having a metal-isulating transition. The changes in the XANES range 10–15 eV above the absorption edge are interpreted based on the known band-structure calculations. The high-energy features are related to the multiple-scattering processes (EXAFS) on the nearest atoms. The intensity of the feature at 550–560 eV is attributed for the first time to the value of the metal-oxygen-metal bond angle.

Tandem Oxidative Cyclization with Rhenium Oxide. Total Synthesis of 17,18-bisepi-Goniocin

Many of the acetogenins isolated from the Annonaceae plants1 have shown remarkable cytotoxic, antitumor, antimalarial, immunosuppressive, pesticidal, and antifeedant activities.2 Classification of these fatty acid derivatives into three subgroups is based on the number and relative positioning of the tetrahydrofuran moieties within the molecule: the mono-THF, the adjacent bis-THF, and the nonadjacent bis-THF acetogenins.1 We have recently shown that many acetogenins of the first and second subgroups, including solamin, reticulatacin, asimicin, bullatacin, trilobacin, and trilobin, can be efficiently synthesized3 either by a convergent approach or via the “naked” carbon skeleton strategy,4,5 combining the Sharpless asymmetric dihydroxylation (AD) reaction6 with the Kennedy oxidative cyclization reaction.7 Goniocin, which has been recently isolated from Goniothalamus giganteus,8 possesses three adjacent THF rings and, therefore, represents the first example of a new subclass of Annonaceous acetogenins. Structure 1 was proposed for goniocin on the basis of its MS and 1H and 13C NMR data.8 Clearly, construction of the tris-trans-THF fragment I with the appropriate configuration of the seven stereogenic carbinol centers represents the main challenge in the synthesis of 1. Our retrosynthetic analysis (Scheme 1) was based on previous findings that two consecutive oxidative cyclizations with 4,8dienols can be carried out in a single step to produce bis-THF derivatives.9 We reasoned that I could be synthesized from a 4,8,12-trienol substrate using the tandem oxidative cyclization methodology. Coupling of I with the butenolide fragment II could lead to an efficient total synthesis of 1. Here, we report that all trans-4,8,12-trienol substrates indeed undergo a highly stereospecific triple oxidative cyclization reaction in the presence of a rhenium(VII) reagent to produce a single stereoisomer of a tris-THF product. Surprisingly, however, the product’s stereochemistry is not trans-threo-transthreo-trans-threo as expected, but trans-threo-cis-threo-cisthreo. Consequently, we have synthesized 17,18-bisepigoniocin (2) rather than 1. The key intermediate in our synthesis (Scheme 2) is the “naked” carbon skeleton (6) which is easily prepared from (E,E)ethyl heneicosa-4,8-dienoate3a (see the Supporting Information). Asymmetric epoxidation10 of 3 using Ti(OPr)4 and (-)-DIPT produces epoxy alcohol 4 in more than 95% ee. Reductive cleavage of the epoxide ring using Red-Al affords the 1,3-diol 5,11 which is then monoprotected at the primary position to give the silyl ether 6. We planned to use the single stereogenic center in 6 as the only source of chirality at the tris-THF fragment and achieve the other six stereogenic carbinol centers by a tandem oxidative cyclization reaction using a Re(VII) reagent. We found that both reagents originally used by Kennedy, i.e. Re2O7/lutidine and Re2O7/H5IO6 in dichloromethane, are useful for monocyclization with simple substrates possessing one double bond. However, for double cyclization with substrates containing two double bonds, the more reactive mixture, Re2O7/H5IO6, was † The Scripps Research Institute. ‡ Technion. (1) Zeng, L.; Ye, Q.; Oberlies, N. H.; Shi, G.; Gu, Z.-M.; He, K.; McLaughlin, J. L. Nat. Prod. Rep. 1996, 275. (2) Gu, Z.-M.; Zhao, G.-X.; Oberlies, N. H.; Zeng, L.; McLaughlin, J. L. In Recent AdVances in Phytochemistry; Arnason, J. T., Mata, R., Romeo, J. T., Eds.; Plenum Press: New York, 1995; Vol. 29, pp 249-310. (3) (a) Sinha, S. C; Keinan, E. J. Am. Chem. Soc. 1993, 115, 4891. (b) Sinha, S. C.; Sinha-Bagchi, A.; Yazbak, A.; Keinan, E. Tetrahedron Lett. 1995, 36, 9257. (c) Sinha, S. C.; Sinha, A.; Yazbak, A.; Keinan, E. J. Org. Chem. 1996, 61, 7640. (d) Sinha, A.; Sinha, S. C.; Keinan, E. Submitted. (4) Keinan, E.; Sinha, A.; Yazbak, A.; Sinha, S. C.; Sinha, S. C. Pure Appl. Chem. 1997, 69, 423. (5) (a) Sinha, S. C; Keinan, E. J. Org. Chem. 1994, 59, 949. (b) Sinha, S. C; Keinan, E. J. Org. Chem. 1997, 62, 377. (c) Sinha, S. C; SinhaBagchi, A.; Keinan, E. J. Org. Chem. 1993, 58, 7789. (6) Kolb, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem. ReV. 1994, 94, 2483. (7) (a) Tang, S.; Kennedy, R. M. Tetrahedron Lett. 1992, 33, 3729. (b) Tang, S.; Kennedy, R. M. Tetrahedron Lett. 1992, 33, 5299. (c) Tang, S.; Kennedy, R. M. Tetrahedron Lett. 1992, 33, 5303. (d) Boyce, R. S.; Kennedy, R. M. Tetrahedron Lett. 1994, 35, 5133. (8) Gu, Z.-M.; Fang, X.-P.; Zeng, L.; McLaughlin, J. L. Tetrahedron Lett. 1994, 35, 5367. (9) Sinha, S. C; Sinha-Bagchi, A.; Keinan, E. J. Am. Chem. Soc. 1995, 117, 1447. (10) (a) Johnson, R. A.; Sharpless, K. B. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.; VCH Publishers Inc.: New York, 1993; p 103. (b) Gao, Y.; Hanson, R. M.; Klunder, J. M.; Ko, S. Y.; Masamune, H.; Sharpless, K. B. J. Am. Chem. Soc. 1987, 109, 5765. (11) (a) Finan, J. M.; Kishi, Y. Tetrahedron Lett. 1982, 23, 2719. (b) Viti, S. M. Tetrahedron Lett. 1982, 23, 4541. Scheme 1

Surface Ionization Organic Mass Spectrometry of s-Triazine Herbicides

Surface ionization organic mass spectrometry (SIOMS) was applied to some s-triazine herbicides (simazine, atrazine, simetryne, ametryne and prometryne) by using quadrupole mass spectrometry in which the thermal ion source has a rhenium oxide emitter. The mass spectra were interpreted in a purely empirical way by means of evidence from previous investigations, and then compared with conventional electron impact ionization techniques. Sensitivity and selectivity were also studied, demonstrating that (i) these herbicides are efficiently surface ionized, (ii) in the SI mass spectra all s-triazines exhibited the M+ molecular ion as the base peak with only relatively minor fragment species, with the exception of prometryne, (iii) the experimental results rationalized the high sensitivity of surface ionization detection (SID) in gas chromatography (GC) for the herbicides examined and (iv) GC/SIOMS coupling can be used for the sensitive and selective detection of these herbicides in the water. An approach to the detection of these herbicides in water by GC/SIOMS and GC/SID is described. The characteristics of both methods provide a reliable, sensitive and selective method which is needed for low concentration level measurements in complex mixtures. © 1997 by John Wiley & Sons, Ltd.

Surface Ionization Organic Mass Spectrometry ofs-Triazine Herbicides

Surface ionization organic mass spectrometry (SIOMS) was applied to some s-triazine herbicides (simazine, atrazine, simetryne, ametryne and prometryne) by using quadrupole mass spectrometry in which the thermal ion source has a rhenium oxide emitter. The mass spectra were interpreted in a purely empirical way by means of evidence from previous investigations, and then compared with conventional electron impact ionization techniques. Sensitivity and selectivity were also studied, demonstrating that (i) these herbicides are efficiently surface ionized, (ii) in the SI mass spectra all s-triazines exhibited the M + molecular ion as the base peak with only relatively minor fragment species, with the exception of prometryne, (iii) the experimental results rationalized the high sensitivity of surface ionization detection (SID) in gas chromatography (GC) for the herbicides examined and (iv) GC/SIOMS coupling can be used for the sensitive and selective detection of these herbicides in the water. An approach to the detection of these herbicides in water by GC/SIOMS and GC/SID is described. The characteristics of both methods provide a reliable, sensitive and selective method which is needed for low concentration level measurements in complex mixture.

高速有機化合物分子の表面電離質量スペクトル： モノテルペン類

This paper describes an experimental study on the influence of kinetic energy of fast monoterpene molecules on the surface ionization efficiency and on the mass spectral patterns, using rhenium oxide (ReO2) surface. Molecular kinetic energy, given to the molecules through the acceleration in the seeded supersonic molecular beam, ranged from 1 to 10 eV. Hyperthermal surface ionization mass spectra (HSIMS) were taken for various incident kinetic energies and surface temperatures. The observed mass spectra were interpreted in a purely empirical way, by means of evidence from the previous investigations, and they were compared with conventional EI techniques and with the thermal energy surface ionization technique (SIOMS; Surface Ionization Organic Mass Spectrometry). Ionization efficiency (β) was also studied.Under hyperthermal surface ionization (HSI) conditions, many kinds of fragment ions, including quite abundant odd electron ions (OE+·) are observed. HSIMS patterns of monoterpenes are different among 6-isomers, contrary to those of SIOMS and EIMS, where very similar patterns for isomers are observed. HSIMS patterns are strongly dependent on the molecular kinetic energies. The surface temperature does not affect much the spectral patterns, but it controls the total amount of ion formation. We conclude from these mass spectral findings, HSI-mechanism contains an impulsive process of ion formation, followed by the fragmentation process as a results of the internal energies acquired through the collision processes.

Towards chemical libraries of annonaceous acetogenins

Abstract

Partial oxidation of methane to formaldehyde on silica-supported transition metal oxide catalysts

This work describes the partial oxidation of methane on high surface area silica-supported redox oxide catalysts (MO x /SiO 2; M = V, Mo, W and Re). Formaldehyde, C 2H n , and CO 2 are primary products obtained in this reaction, while CO originates from further oxidation of formaldehyde and hydrocarbons. Supported vanadium oxide was found to be the most reactive due to its higher reducibility, thus providing additional sites for oxygen activation. Rhenium oxide exhibited high specific activity and selectivity, however it deactivates from sublimation of metal oxide under on-stream operation at high temperatures, typically above 773 K. Results suggest a reaction scheme where oxygenates and oxygen-free intermediates are present yielding HCHO, CO x and C 2H n hydrocarbons.

The dynamic states of silica-supported metal oxide catalysts during methanol oxidation

The in situ Raman spectra of silica-supported metal oxide catalysts (containing surface metal oxide species of V, Nb, Cr, Mo, W and Re) were measured during methanol oxidation. Stable surface methoxy species were found to form via reaction with the surface SiOH groups for all the catalysts investigated. The surface SiOH groups were also titrated by the surface metal oxide species and the surface concentration of SiOH groups decreases with increasing metal oxide loading. The stable surface MOCH 3 were only found for the V 2O 5/SiO 2 catalysts. The surface metal oxide species were all influenced by the methanol oxidation reaction. The surface rhenium oxide species were removed from the silica surface and the surface molybdenum oxide species were partially agglomerated to crystalline β-MoO 3 particles by the formation of Re-methoxy and Mo-methoxy complexes. The surface niobium oxide and tungsten oxide species were partially reducing by the net reducing methanol oxidation environment. In situ Raman spectra for the CrO 3/SiO 2 catalysts could not be obtained due to the formation of reduced chromium oxide species during methanol oxidation which gave rise to sample fluorescence. The in situ Raman observations provided a fundamental basis for understanding the selectivity patterns of the silica-supported metal oxide catalysts during methanol oxidation. However, the mechanism by which the silica support ligands activate the redox properties of the surface metal oxide species is not completely understood.

A Surface Ionization Detector for Gas Chromatography: Use of a Supersonic Free Jet

A new design of a gas chromatographic surface ionization detector (SID) based on hyperthermal positive surface ionization is described. There are two requirements: use of a supersonic free jet nozzle and the high-work-function surface of rhenium oxide. This detector, which is sensitive in response to all the organics, can be operated as an universal detector with much higher sensitivity toward some species having low ionization energy but with selectivity to a lesser degree than that of a conventional SID. The minimum detectable amount (at S/N = 3) of pyrene is around 4.4 × 10(-)(13) g/s, with linearity greater than 10(6), while that of toluene is around 10(-)(12) g/s. Other unique properties are (1) the ability to control the degree of selectivity through molecular kinetic energy, the surface, and its temperature and (2) a very short response time.

Crystal Structure and Magnetic Properties of Sm3ReO7

Crystals of a new ternary samarium rhenium oxide, Sm3ReO7were obtained by subsolidus reaction of samariumsesquioxide and rheniumdioxide (ratio 1.5:1) in sealed Pt–10Rh-tubes at 1673 K. The structure was determined by single-crystal X-ray diffraction. Sm3ReO7crystallizes in the orthorhombic system with unit cell dimensionsa= 10.736(5),b= 7.392(3), andc= 7.519(3) in space groupCmcm(No. 63) withZ= 4. The structure consists of ReO6octahedra, distorted SmO6octahedra, and SmO8prisms that are interconnected to each other to form a three-dimensional network. Rhenium has the formal oxidation state of +5 but no metal–metal bond is observed in this compound. The observed magnetization in the temperature range 4 K <T< 52 K is explained by a Curie–Weiss law modified by a temperature independent Van Vleck paramagnetism of samarium (3+).

Cluster chemical ionization and deuterium exchange mass spectrometry in supersonic molecular Beams

A cluster-based chemical ionization method has been developed that produces protonated molecular ions from molecules introduced through a supersonic molecular beam interface. Mixed clusters of the analyte and a clustering agent (water or methanol) are produced in the expansion region of the beam, and are subsequently ionized by "fly through" electron impact (EI) ionization, which results in a mass spectrum that is a combination of protonated molecular ion peaks together with the conventional EI fragmentation pattern. The technique is presented and discussed as a tool complementary to electron impact ionization in supersonic molecular beams. Surface-induced dissociation on a rhenium oxide surface is also applied to simplify the mass spectra of clusters and reveal the analyte spectrum. The high gas flow rates involved with the supersonic molecular beam interface that enable the easy introduction of the clustering agents also have been used to introduce deuterating agents. An easy-to-use, fast, and routine on-line deuterium exchange method was developed to exchange active hydrogens (NH, OH). This method, combined with electron impact ionization, is demonstrated and discussed in terms of the unique information available through the EI fragmentation patterns, its ability to help in isomer identification, and possible applications with fast gas chromatography-mass spectrometry in supersonic molecular beams.

The Selective Catalytic Reduction of NOxwith NH3over Titania Supported Rhenium Oxide Catalysts

The Selective Catalytic Reduction of NOxwith NH3over Titania Supported Rhenium Oxide Catalysts

XANES studies on rhenium L absorption edges of Re 2O 7 graphite intercalation compounds and of other rhenium-oxygen compounds

The electronic structure as well as the medium-range order of rhenium oxides and Re 2O 7 graphite intercalation compounds (GICs) were investigated by analyzing the XANES (X-ray absorption near edge structure) of the Re L I–III absorption edges. The Re L I,III edges show for all perrhenates strong white lines whose full widths decrease going from the solid to the highly concentrated to the highly diluted solution. Coincidently the area of the white lines increases. The GICs show the same dependence with the exception that their absorption peaks are always lower, which is caused by a charge transfer from graphite to rhenium. A reduced intensity of the strong pre-edge peak at the Re L I edges in comparison to solid perrhenates and perrhenate solutions indicates a slightly distorted tetrahedral symmetry for the GICs. The analysis of a multiple scattering feature at the Re L I edge reveals for the GIC intensities similar to the solutions but several times lower than those of the solid perrhenates. The loss of the three-dimensional long-range order after the intercalation accompanied by a low density of ReO 4 tetrahedra causes this effect.