Abstract: A tetranuclear ferric Keggin sandwich-type heteropolyanion has been synthesized by the reaction of the lacunary species Δ-Na8H[PW9O34] with FeCl2 followed by O2 oxidation in nonaqueous media. The structure of [(n-C4H9)4N]6[FeIII4(H2O)2(PW9O34)2]·4CH3CN·2CH2Cl2·2H2O (TBA-1) was determined by single-crystal X-ray diffraction (orthorhombic, Pbca; R = 0.0693 for 14 963 reflections with Fo > 4σ(Fo)). The compound was further characterized by infrared and UV−visible spectroscopy, electrochemistry, magnetic susceptibility, FAB mass spectrometry (FAB-MS), and elemental analyses. Five lines of evidence are consistent with the FeIII4 oxidation state: (i) valence sum calculations from the X-ray structure (ca. 2.86 ± 0.07 per Fe); (ii) the rest potential from cyclic voltammetry; (iii) charge balance requirements; (iv) titration with CeIV(SO4)2; and (v) oxidation by O2. In contrast to the tetranuclear ferric Wells−Dawson-derived sandwich complex, [FeIII4(H2O)2(P2W15O56)2]12-, TBA-1 can only be prepared from a ferrous...

Abstract: The synthesis and characterization of a phosphinoalkylarene, redox-switchable hemilabile ligand (RHL), (η5-C5H5)Fe(η5-C5H4C6H4OCH2CH2PPh2) (1), are reported. This ligand, which incorporates a redox-active ferrocenyl group, exhibits oxidation-state-dependent bonding properties and, hence, affords electrochemical control over the electronic and steric environments of bound transition metal centers. Two equivalents of 1 complex to Rh(I) to yield a bis(phosphine), η6-arene complex [(η1:η6-(η5-C5H5)Fe(η5-C5H4C6H4OCH2CH2PPh2))(η1-(η5-C5H5)Fe(η5-C5H4C6H4OCH2CH2PPh2))Rh]+BF4- (2). Single-crystal X-ray diffraction studies of 2·1.25CH2Cl2, as well as solution spectroscopic data of 2, are consistent with this formulated piano-stool geometry. Foremost, the properties of 2 as a function of bound RHL state-of-charge are extensively investigated. Interestingly, 2D 1H NMR exchange spectroscopy (EXSY) studies demonstrate significantly faster intramolecular η6-arene, free arene exchange rates only upon oxidation of the lig...

Abstract: An analysis of 250 MnOn fragments retrieved from the Cambridge Structural Database was used to derive the oxidation state independent R0 value of 1.754 A for Mn−O bonds that can be used to reproduce the oxidation state using the bond valence sum (BVS) method. The coordination numbers varied from 3 to 8 and the oxidation states from 2 through 7. Deviations of the BVS from an integer value are discussed. An analysis of the 1360 Mn−O bond distances used suggests that the BVS is more significant in discussing Mn−O structures than a comparison of bond distances.

Abstract: The catalytic behavior of a chromium-doped alumina pillared clay (ACrPA) and a series of chromia-pillared clay materials (XSCr) for the deep oxidation of methylene chloride has been studied. Both types of catalysts showed a high activity (conversion > 80%) at T > 350°C. The ACrPA sample showed a virtually constant catalytic activity (conversion > 99%) in the 300–400°C temperature range while the activity of the XSCr samples markedly increased with the temperature reaching an almost total conversion at 400°C. XPS (X-ray photoelectron spectroscopy) and temperature programmed reduction (TPR) studies demonstrated that ACrPA is a Cr(VI) Cr(III) mixed valence catalyst, whereas XSCr samples contain only chromium(III) ion. The high activity shown by ACrPA at low temperatures was attributed to the presence of highly dispersed Cr(VI) species, which exhibited an unusually high stability. The metal oxidation state of the two chromium based systems seemed to be important in determining the catalytic activity. The increase of the activity with the Cr content in XSCr samples suggested that the acid sites in these catalysts were located on the chromia pillars.

Abstract: The role of the electrons and holes at the surface of semiconductor oxides (TiO 2 and WO 3 ) in heterogeneous photocatalysis has been investigated in aqueous media for the reactions involving the series: nitrobenzene, nitrosobenzene, phenylhydroxylamine, aniline, and the related compound, 4-nitrosophenol. Qualitative and quantitative evaluation of most intermediates and their time evolution suggest that the reductive pathways are important and even predominant under a variety of experimental conditions. This aspect is not only true at the beginning of the process or for the readily reducible structures, but also during the entire degradation process. Each compound of the series is converted to all the others, even though in widely different amounts. In the early part of the photocatalytic process, with nitrosobenzene and with phenylhydroxylamine, even in the presence of oxygen, the nitrogen substituent undergoes simultaneous oxidation and reduction at comparable rates, so that very little change in the mean oxidation state of the system is observed. This suggests that photogenerated electrons have a controlling role, particularly for some compounds in the early steps of the photocatalytic transformation. For 4-nitrosophenol and p-benzoquinone, in the early steps of degradation the reductive pathways represent the main route, even in the presence of oxygen. As a consequence, for some compounds the presence of an excess of oxygen in the reacting atmosphere decreases the degradation rate, instead of promoting it, as is commonly observed in photocatalysis. It is also remarkable that, for some compounds examined, the redox reactions at the nitrogen-containing substituent have a comparable or even more important role than the hydroxylation of the aromatic ring, which was the predominant degradation pathway for most of the other aromatic compounds.

Abstract: The binding and oxidation of an artificial substrate, 2-aminothiazole, by an engineered cavity of cytochrome c peroxidase is described. The W191G mutant has been shown to create a buried cavity into which a number of small heterocyclic compounds will bind [Fitzgerald, M. M., Churchill, M. J., McRee, D. E., & Goodin, D. B. (1994) Biochemistry 33, 3807-3818], providing a specific site near the heme from which substrates might be oxidized. In this study, we show by titration calorimetry that 2-aminothiazole binds to W191G with a Kd of 0.028 mM at pH 6. A crystal structure at 2.3 A resolution of W191G in the presence of 2-aminothiazole reveals the occupation of this compound in the cavity, and indicates that it is in van der Waals contact with the heme. The WT enzyme reacts with H2O2 to form Compound ES, in which both the iron center and the Trp-191 side chain are reversibly oxidized. For the W191F (and perhaps the W191G) mutants, the iron is still oxidized, but the second equivalent exists transiently as a radical on the porphyrin before migrating to an alternate protein radical site [Erman, J. E., Vitello, L. B., Mauro, J. M., & Kraut, J. (1989) Biochemistry 28, 7992-7995]. Two separate reactions are observed between 2-aminothiazole and the oxidized centers of W191G. In the one reaction, optical and EPR spectra of the heme are used to show that 2-aminothiazole acts as an electron donor to the ferryl (Fe4+dO) center of W191G to reduce it to the ferric oxidation state. This reaction occurs from within the cavity, as it is not observed for variants that lack this artificial binding site. A second reaction between 2-aminothiazole and peroxide-oxidized W191G, which is much less efficient, results in the specific covalent modification of Tyr-236. Electrospray mass spectra of the W191G after incubation in 2-aminothiazole and H2O2 show a modification of the protein indicative of covalent binding of 2-aminothiazole. The site of modification was determined to be Tyr-236 by CNBr peptide mapping and automated peptide sequencing. The covalent modification is only observed for W191G and W191F which form the alternate radical center. This observation provides an unanticipated assignment of this free radical species to Tyr-236, which is consistent with previous proposals that it is a tyrosine. The oxidation of 2-aminothiazole by W191G represents an example of how the oxidative capacity inherent in the heme prosthetic group and the specific binding behavior of artificial protein cavities can be harnessed and redirected toward the oxidation of organic substrates.

Abstract: A new expression is devised empirically to accommodate zero and some negative oxidation states in the bond-valence sum approach. The method is worked out in detail for a number of homoleptic copper and nickel complexes of various coordinating atoms in several oxidation states of the metals. An implication of the expression is a linear variation between 1/req and 1/rax in octahedral MX6 moieties, where req and rax are, respectively, the average equatorial and axial bond lengths. This is verified in Cu2+X6 chromophores for X = F, O, N and S. The usefulness of the new expression in assessing the compatibility of a coordination sphere with an oxidation state of a metal ion is demonstrated by exemplary applications to some inorganic complexes, azurin and urease.

Abstract: A series of new “magic number” metal oxide clusters are described for the group V metals antimony and bismuth. Specific nonstatistical stoichiometries of MxOy cation and anion clusters are formed preferentially in the gas phase when oxidized metal is vaporized or when metal is vaporized and combined with gas phase oxygen (e.g., Bi7O10+, Bi9O14+). Essentially the same stoichiometries are seen for antimony and bismuth analogues. The species produced in cluster growth are also produced preferentially by photodissociation of larger clusters. Localized covalent bonding schemes are suggested for these clusters, and polyhedral cage structures are proposed. The stoichiometries observed require a 3+ metal oxidation state in the small clusters, which shifts over to one or more 5+ metal atoms in larger clusters.

Abstract: A method of dissolving in an ionic liquid a metal in an initial oxidation state below its maximum oxidation state, characterised in that the ionic liquid reacts with the metal and oxidises it to a higher oxidation state. The initial metal may be in the form of a compound thereof and may be irradiated nuclear fuel comprising UO2 and/or PuO2 as well as fission products. The ionic liquid typically is nitrate-based, for example a pyridinium or substituted imidazolium nitrate, and contains a Bronstead or Franklin acid to increase the oxidising power of the nitrate. Suitable acids are HNO3, H2SO4 and [NO+]. Imidazolium nitrates and certain pyridinium nitrates form one aspect of the invention.

Abstract: The insertion of InBr into the Au−Br bond of [(Ph3P)AuBr] in tetrahydrofuran (thf) in the presence of [(CH2PPh2)2] (dppe) leads to the formation of an orange complex [(dppe)2Au]+[(dppe)2Au3In3Br7(thf)]-, 2. Analytical, spectroscopic, and X-ray structural investigations showed that this product is an anionic analogue of a neutral chloride complex [(dppe)2Au3In3Cl6(thf)3], 1, prepared recently. Both complexes have an Au3In3 cluster core of approximate C2v symmetry with one extremely short Au−Au bond [Au1−Au3 2.575(1) A] as part of a quasi-linear array P1−Au1−Au3−P4, suggesting the presence of a bis(phosphine) complex of the neutral Au2 molecule as part of the cluster. The third gold atom (Au2) is then assigned oxidation state +1. To gain deeper insight into the structure and bonding of this novel class of gold cluster compounds, regarding mainly the peculiar cluster geometry, the charge distribution, and the oxidation states, a series of scalar relativistic all-electron density functional (DF) calculations ...

Abstract: X-ray photoelectron spectroscopy was applied for Ziegler-Natta catalysts and the oxidation state of titanium chloride was studied from the analysis of the Ti 2 p 3 2 peak. It was observed that the state of titanium chloride on the catalysts was changed by the reaction with the co-catalyst.

Abstract: The reactions of acetone were investigated on α U3O8 (stoichiometric and H2 reduced) by temperature programmed desorption. The surface and bulk characteristics of U oxides were investigated by x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD). The comparison between the XPS U 4f7/2 binding energy of β UO3, α U3O8, and UO2 indicated that the U cations in U3O8 are composed of +5/+6 (2/1) or +4/+6 (1/2) oxidation states. XPS of H2 reduced α U3O8 (at 800 K) indicated a shift of the U 4f7/2 binding energy from 381.6 (unreduced) to 380.5 eV (reduced) as well as the appearance of two satellites at 387.0 and 397.4 eV. These new XPS lines’ positions are characteristic of U+4 cations of UO2. Similar results were observed upon Ar-ion sputtering of α U3O8. Ar-ion sputtering of β UO3 also results in the reduction of U+6 cations to U+4 cations. XRD of H2 reduced α U3O8 indicated that all of the α U3O8 phase was transformed to the UO2 phase. A considerable difference between the reactivity of the surfaces of U3O8 and UO2 towards acetone was observed. A carbon–carbon bond formation reaction giving isobutene was observed only on the α U3O8 surface indicating its structure-sensitive nature and/or its sensitivity towards changing the oxidation state of U cations. This reaction has not been observed on the surfaces of actinide oxides before. On the other hand, acetone reacted on UO2 to give mainly propene. This latter reaction (which is a C–O bond dissociation) is most likely due to the capacity of UO2 to accommodate large numbers of atomic oxygen in interstitial positions while maintaining its structure intact.

Abstract: The adsorption of C60 in submonolayer and monolayer coverages on Cs-precovered Au(110) has been investigated by photoemission and high-resolution electron-energy-loss spectroscopy Complete fullerene monolayers display discrete molecular oxidation states of approximately -3, -4, and -6 in the presence of Cs The oxidation states were determined by a comparison of monolayer electronic structure and vibrational mode frequencies with those of the bulk fullerides There is no evidence for oxidation states of -2 and -5 Surface-specific measurements on bulk vacuum distilled alkali-fulleride samples showed a strong similarity between the properties of the single-layer films and the surface layers of the bulk material Annealing experiments demonstrated that it was possible to produce a well-ordered, close-packed monolayer of C60 with an oxidation state of -3, which may be a useful precursor in producing a metastable fcc Cs3C60 film by epitaxial growth Bonding with the substrate stabilized this film with respect to bulk samples leading to desorption only at temperatures >900 K Electron-energy-loss spectroscopy of submonolayer C60 in the presence of multilayers of Cs indicates that filling of the lowest unoccupied molecular orbital (LUMO)+1 states occurs Completion of the monolayer results in extra charge occupying the LUMO band only However, LUMO+1 occupation can also be brought about by sandwiching complete fullerene monolayers between Cs layers

Abstract: The mobility of Cr n+ in inorganic oxides has been investigated by combined diffuse reflectance (DR)–EPR spectroscopies as a function of the Cr oxidation state, the type of inorganic oxide (silica, alumina and mordenite) and the environmental conditions (hydrated and dehydrated state). Cr n+ ions are mobile under hydrated and dehydrated conditions and Cr n+ preferentially migrates from silica to alumina and, to a lesser extent, to mordenite, although only a small amount of migration of Cr n+ is observed from alumina to mordenite and vice versa. The observed preference sequences are discussed in relation to the properties of the inorganic oxides.

Abstract: Disclosed is a process for oxidizing volatile organic compounds to carbon dioxide and water with the minimal addition of energy. A mixture of the volatile organic compound and an oxidizing agent (e.g. ambient air containing the volatile organic compound) is exposed to a catalyst which includes a noble metal dispersed on a metal oxide which possesses more than one oxidation state. Especially good results are obtained when the noble metal is platinum, and the metal oxide which possesses more than one oxidation state is tin oxide. A promoter (i.e., a small amount of an oxide of a transition series metal) may be used in association with the tin oxide to provide very beneficial results.

Abstract: Publisher Summary This chapter discusses several studies where the researchers have synthesized a number of vanadium, containing sodium super-ionic conductor (NASICONS), characterized them, and checked the catalytic properties of some of them for the oxidation of n-butane. The synthesized compositions have been characterized by X-ray diffraction and the results are discussed in the chapter. Most of the NASICON phases that have been synthesized are relatively pure. Magnetic susceptibility measurements of two of the synthesized compositions strongly suggest that the majority oxidation state of vanadium in these NASICON phases is V4+. The respective measured values are 1.57 BM for NbVP3O12 and 2.13 BM for SbVP3O12. The composition of NbTi0.75V0.25P3O12 exhibits an X-ray diffraction (XRD) pattern characteristic of a NASICON structure and has a surface area of 16.9 m 2/g. The catalytic properties of this phase have also been investigated for the oxidation of n-butane and are discussed in the chapter. The results reveal that this composition possesses catalytic properties, activates n-butane under oxidizing conditions, and converts it to maleic anhydride and waste products, CO and CO2. The sole nonCOx product is maleic anhydride. The Nb-Ti-V-P-oxide catalyst investigated is relatively active for the oxidation of paraffins, as it has a V/P ratio of only 1/12 as compared to a 1/1 ratio for (VO)2P2O7. Another observed fact is that the Nb-Ti-V-P-oxide under investigation shows an amorphous overlayer via transmission electron microscopy (TEM) that is enriched in vanadium. Future studies are underway to further refine the syntheses methods and isostructural key catalytic element substitutions to achieve the desired goals of rational catalyst design, and thereby influencing the reaction channels of oxidation reactions.

Abstract: A simple method for determining the oxidation state of the Ti in complexes involving only N, O, or Cl donors using the bond valence sum, henceforth BVS, is proposed. New R0 values of 1.906 for Ti−N, 1.790 for Ti−O, and 2.184 for Ti−Cl were determined from TiLn complexes where L was N, O, or Cl and n varied from 4 to 7. These R0 values were then used to calculate the BVS for 534 Ti complexes with coordination numbers of 4−7 and only N, O, or Cl as donor atoms. Examples where the BVS was a noninteger value or differed from the reported oxidation state are discussed.

Abstract: The crystal structure of the title compound, where TTM–TTP is 2,5-bis [4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, has been determined by X-ray analysis. The donors form a uniform stack, which is responsible for metallic conduction down to TMI = 20 K. The anions are composed of discrete I3− and an infinite chain of I3−. Each donor has anomalously large positive charge of +5/3.

Abstract: The tin reduction during lithium insertion in spinel sulfide compounds is investigated. Mossbauer and RMN spectroscopy are combined with tight binding calculations to analyze the reduction mechanism. It is shown that the formal reaction SnIV + 2e- → SnII is involved without an intermediate Sn oxidation state. The following mechanism is proposed: lithium ions create shallow and deep-defect donor states; the trapping of two electrons on the deep one, which exhibits a negative U behavior, induces the reduction of the corresponding tin atom.

Abstract: The Cu 2P3/2 photoelectron spectra were acquired to study the coordination state and oxidation state of Cu in ZSM-5 in the NO reduction by propene in the presence of excess oxygen. Two peaks at hig...

Abstract: 1. Some Basic Concepts 2. Atoms and Atomic Structure 3. Homonuclear Covalent Bonds 4. Heteronuclear Diatomic Molecules 5. Polyatomic Molecules: Shapes and Bonding 6. Ions 7. Elements 8. Alkanes, Alkenes and Alkynes 9. Spectroscopy 10. Reaction Kinetics 11. Hydrogen and the s-Block Elements 12. Thermodynamics and Electrochemistry 13. p-Block and High Oxidation State d-Block Elements 14. Polar Organic Compounds Rings 15. Co-ordination Complexes of the d-Block Metals 16. Carbonyl Compounds

Abstract: In this work we have studied the interfacial reactions between chromium and an Al 2 0 3 (1102) surface with X-ray photoelectron spectroscopy and Auger electron spectroscopy. The results reveal that, at room temperature, the interfacial reactions are dominated by the interaction of Cr atoms with the oxygen anions on the Al 2 O 3 substrate forming a Cr-O-Al complex oxide. Annealing the Cr-covered sample to high temperature, additional interfacial reactions occur, involving the formation of chromium oxide and metallic Al, indicating the interfacial reactions have a strong temperature dependence. The results also show that the relative Auger peak-to-peak height (APPH) of the Cr LMM group peaks is very sensitive to the change of the valence band structure, therefore, it can be used as an index to identify the oxidation state of chromium at the Cr/Al 2 O 3 interface.