Abstract: Oxidation state changes, completeness of oxidation, and densities of anodically formed, electrochromic iridium oxide films have been determined by combined gravimetric, coulometric, and reflection spectroscopy analyses. The results show that the oxidation state of Ir ions in the oxide is changed from III to IV during the anodic coloration process [0.25 to 1.25V (RHE)], rather than II to IV as previously postulated, and that virtually all Ir ions in the film are accessible for electrochemical oxidation and reduction. The mean density of the oxide film is 2.0g cm−3, as compared to 11.68 for bulk crystalline . The structure of the film was shown by electron microscopy to consist of oxide grains 0.05–0.1 μm in diameter, surrounded by voids. In addition, the presence of a high density of microvoids ~25A in diameter was detected. The highly porous structure of the film permits ready access of the electrolyte to the oxide grains throughout the entire film and facilitates the rapid coloration and bleaching (~40 msec) observed in aqueous electrolytes. The apparent accessibility of all Ir ions in the film also implies rapid transport, within the oxide grains, of the mobile charge‐compensating ions which must be injected and ejected to preserve electroneutrality. Mechanisms of ion and electron transport are discussed.

Abstract: The method of direct electrochemical synthesis consists of oxidizing a metal anode in a non-aqueous solution containing a ligand (or ligand precursor) to produce the appropriate inorganic or organometallic compound. In many cases, the product precipitates directly in the cell, making for easy isolation, so that the technique is both direct and simple, and in addition the product yields are very high. One advantage of the technique is that the products are often derivatives of a low oxidation state of the metal; \examples of this include chromium(III) bromide, tin(II) and lead(II) diolates and thiolates, hexahalogenodigallate(II) anions, thorium diiodide, copper(I) thiolate complexes, and indium(I) derivatives of thiols, dithiols, and diols. In some systems, the low oxidation state compound undergoes subsequent reaction; for example, in the synthesis of RInX2 the reaction sequence involves the oxidation of indium metal to give InX, which then reacts with RX to give RInX2. Another possible post-electrolysis process is disproportionation. Examples of these various preparative routes will be discussed.

Abstract: : This paper presents an investigation of oxidation state and charge transport in the low-dimensional materials Ni(dpg)2Br1.0 and Pd(dpg)2Br1.1, dpg = diphenylglyoximato. Resonance Raman structure-spectra correlations are discussed for polybromides, and Br5 is assigned as the predominant halogen species in both of these materials. Thus, the M(dpg)2 units are formally in fractional oxidation states of ca. +0.20(2) (M=Ni) and +0.22(2) (M=Pd). In the optical spectra of both materials, a broad transition at 500 nm is related to the polybromide chains. Four-probe single crystal electrical conductivities (dc) in the stacking direction at 300 K are as high as .00091/omega cm (Ni(dpg)2Br1.0) and .00015/omega cm (Pd(dpg)2Br1.1). The conductivity is demonstrated to be thermally activated with activation energies of 0.33 and 0.21 eV, respectively. The transport properties of the brominated materials are found to be very similar to those of the related M(dpg)2I materials (M=Ni, Pd), a result contrary to expectations if the halogen chains were the major charge carrier. (Author)

Abstract: New hexadentate ligands (HRR'Y) generated by reaction of isonitroso ketones with tetraethylenepentamine in 1:1 ratio yield pscudooctahedral nickel(II) complexes Ni(HRR'Y)(CIO 4 )Dq≈1250 cm -1 ;μ eff ≈3μ B ). These are oxidized by alkaline ammonium persulfate to produce red crystals of Ni(RR'Y)(CI0 4 ) 2 which (i) oxidize iron(II) to iron(III), the reaction stoichiometry being Fe:Ni=1:1, (ii) have μ eff ≈2.1 μB, (iii) exhibit polycrystalline EPR spectra characteristic of S=1/2 in axial field (gp≈2.04; g⊥≈2.14), and (iv) undergo a ono-electron electrochemical reduction but no oxidation. Thus Ni(RR'Y)2+ contains nickel in the oxidation state +3. Extensive cyclic voltammetric studies have led to the identification of the following quasi-reversible process near pH 6: Ni(RR'Y) 2+ +e - + H + Ni(HRR'Y) 2+ with E°′ 298 ≈0.68 V vs. SCE. No sign of the formation of nickel( IV) species could be detected up to +0.9 V. Comparison of the ocnnplexing behavior of the various amine-imine-oxime ligands described in this paper and elsewhere and the various oxidation states of nickel achievable with each suggests that for each unit increase (above +2) in the oxidation state of the metal, the presence of at least one oxime function is needed. The HRR'Y ligand system having only one oxime function stabilizes nickel(III) but not nickel(IV). The low-spin iron(II) complexes Fe(HRR'Y)(C10 4 ) 2 are also reported. The IR and electronic spectra of these and the nickel(II) and nickel(III) complexes are described and compared. The iron(II) and nickel(III) complexes exhibit MLCT and LMCT transitions, respectively, in the visible region (∼500 nm).

Abstract: Oxidative dehydrogenation of butenes was investigated by use of a flow reactor over three iron oxide catalysts having different structures, i.e., α-Fe2O3, γ-Fe2O3, and Fe3O4, which were prepared in situ by controlled reduction and reoxidation with a pulse method. Under the working conditions of catalytic oxidation, the structures of α- and γ-Fe2O3 remained unchanged, while Fe3O4 was oxidized to γ-Fe2O3, the oxidation state of iron being Fe(III) in all of three iron oxide catalyst. These results are consistent with the kinetics that the reaction was of zeroth order in the partial pressure of oxygen and of nearly first order in the butene partial pressure. γ-Fe2O3, as well as γ-Fe2O3 formed from Fe3O4 under the catalytic conditions, was very active and selective for the reaction, as expected from the results obtained previously with a pulse reactor. It was concluded from the following facts that the oxygen species responsible for this reaction is lattice oxygen of γ-Fe2O3 and that the reaction proceeds by t...

Abstract: The cation [Fe(NCMe)6]2+ is formed from reactions in acetonitrile of iron metal with WF6, MoF6, PF5, or the NO+ cation and from the reaction of iron(II) fluoride with PF5. Oxidation to FeIII is not observed using binary fluorides or NO+, but [Fe(NCMe)6]2+ is oxidised by chlorine in MeCN to give the tetrachloroferrate(III) anion. The MeCN co-ordinated to FeII is replaced by trimethyl phosphite giving [Fe(NCMe){P(OMe)3}5]2+ as the final product at room temperature. Some of the intermediate complexes in this reaction have been identified in solution by 31P{1H} n.m.r. spectroscopy.

Abstract: New hexadentate ligands (HRR'Y) generated by reaction of isonitroso ketones with tetraethylenepentamine in 1:1 ratio yield pscudooctahedral nickel(II) complexes Ni(HRR'Y)(CIO 4 )Dq≈1250 cm -1 ;μ eff ≈3μ B ). These are oxidized by alkaline ammonium persulfate to produce red crystals of Ni(RR'Y)(CI0 4 ) 2 which (i) oxidize iron(II) to iron(III), the reaction stoichiometry being Fe:Ni=1:1, (ii) have μ eff ≈2.1 μB, (iii) exhibit polycrystalline EPR spectra characteristic of S=1/2 in axial field (gp≈2.04; g⊥≈2.14), and (iv) undergo a ono-electron electrochemical reduction but no oxidation. Thus Ni(RR'Y)2+ contains nickel in the oxidation state +3. Extensive cyclic voltammetric studies have led to the identification of the following quasi-reversible process near pH 6: Ni(RR'Y) 2+ +e - + H + Ni(HRR'Y) 2+ with E°′ 298 ≈0.68 V vs. SCE. No sign of the formation of nickel( IV) species could be detected up to +0.9 V. Comparison of the ocnnplexing behavior of the various amine-imine-oxime ligands described in this paper and elsewhere and the various oxidation states of nickel achievable with each suggests that for each unit increase (above +2) in the oxidation state of the metal, the presence of at least one oxime function is needed. The HRR'Y ligand system having only one oxime function stabilizes nickel(III) but not nickel(IV). The low-spin iron(II) complexes Fe(HRR'Y)(C10 4 ) 2 are also reported. The IR and electronic spectra of these and the nickel(II) and nickel(III) complexes are described and compared. The iron(II) and nickel(III) complexes exhibit MLCT and LMCT transitions, respectively, in the visible region (∼500 nm).

Abstract: Publisher Summary This chapter discusses the catalytic reactions induced by transition metal complexes solvated in zeolite matrices such as oxidation, carbonylation, and related reactions. The electronic structure of the transition metal ion is certainly of importance even though its effects could not be correctly evaluated. The activation mode of both reagents as well as the Redox potential, which greatly affects the kinetic parameters, is primarily determined by the TMI electronic structure. In a number of studies, oxygen was shown to be activated associatively or dissociatively on various TMI and TMIZ where the cations were usually at a low oxidation state. Propylene also adsorbs in various ways on TMIZ, and thus equilibration of Pd II, Cu II, Ni II Y with propylene invariably resulted in a one electron reduction of the transition metal ion and presumably in the formation of the propylene positive radical. Despite the lack of experimental spectroscopic and kinetic data, as far as selective oxidation is concerned, general mechanistic schemes can be tentatively postulated, relying particularly on widely accepted schemes in homogeneous catalysis for soluble homologs of the transition metal complexes hosted in zeolites.

Abstract: 57 Fe Mossbauer parameters of several [Fe6M2S8(SR)9]3–(where M = Mo or W) complexes and [Fe6W2S8(OMe)3(SPh)6]3– have been obtained at 4.2, 77, 195, and 293 K. These are seen to be very similar to those obtained for [Fe4S4(SR)4]2– complexes and, on the basis of the isomer shift, each iron atom is considered to have a net oxidation state of ca. 2.5, thus implying that each molybdenum or tungsten atom has an oxidation state between 3 and 4. Electrochemical reduction of the trianions to the 4–, 5–, 6– and, in some instances, 7– species has been monitored. The first of these reductions occurs at a potential virtually identical to that of the corresponding [Fe4S4(SR)4]2– complex, the second reduction occurs at a potential ca. 200 mV more negative. These two reductions generally appear to be reversible for most of the complexes in acetonitrile solution. However, rapid scan, staircase cyclic voltammetry showed that only [Fe6M2S8(SEt)9]3–(M = Mo or W) in acetonitrile solution approach good electrochemical reversibility.

Abstract: Chemical shifts, ΔE, of the K-absorption discontinuity in several compounds of copper possessing formal oxidation states between 0 and III have been measured. The shifts show a parabolic dependence on the formal oxidation state as well as on the effective atomic charge, q, on copper. Anomalous chemical shifts shown by some of the compounds are discussed in terms of the bonding in these compounds. The ΔE values have also been correlated with the core electron binding energies obtained from X-ray photoelectron spectroscopy.

Abstract: : In contrast the chemistry of the organometallic derivatives of the main-group elements has focused on the properties and reactions of compounds with the metals in their highest oxidation states. Consequently, the literature contains very few examples of well-defined, kinetically stable, low oxidation state organometallic compounds or of reactions in which the main-group metal in an organometallic derivative changes oxidation state. The compounds, In(C5H5) and T1(C5H5), are the only examples of low oxidation state Group III organometallic derivatives. Both of these compounds exist in the solid state as linear polymers with the cyclopentadienyl ring exhibiting pentahapto coordination. In Group IV chemistry, the unique low oxidation state compounds M sub IV(CH(SiMe3)2)2 (M sub IV equal Ge, Sn, Pb) have been prepared and thoroughly characterized. An X-ray structural study of the tin compound confirms a dimeric structure which has an apparent bent tin-tin double bond using the available electron pair and vacant orbital on each tin(II) atom.

Abstract: A study is made to determine the redox equilibria of chromium ions and the factors affecting these equilibria in a soda-lime-silica-glass. The concentrations of individual oxidation states of chromium are determined by both physical and chemical methods. The results of the two methods are found to be in good agreement. Sulfate added as saltcake is seen to shift the equilibrium towards higher hexavalent chromium concentration, whereas iron present in the batch hinders this transformation and stabilizes trivalent chromium until all iron present in the glass is converted to the ferric state. Cobalt, on the other hand, has no effect on this equilibrium. Provided that the sulfate and iron contents of the batch are well adjusted, the redox of the batch and the furnace atmosphere during melting have little effect on the oxidation state of the chromium atoms in the final glass. Consequently, it has been possible to apply the results of the laboratory scale melts directly to the industrial furnaces.

Abstract: White et al. ( 1 ) have claimed that the reaction between tissues and the osmium tetroxide-ferrocyanide reagent leads predomi nantly to Osmium (IV) species. The principal evidence in support of this idea is the similarity between the ESCA data for some model 2,2’-dipyridyl and 1,10-phenanthroline osmium complexes and the ESCA data for fixed tissues. I point out that the dipyridyl complex which they describe is the well-known oxoosmium (VI) complex first reported by Ray and Sarkar in 1966 (2, 3). The phenanthroline complex has an analogous structure (4). Both probably exist in monc)meric and dimeric forms (4). The most readily identifiable characteristic of such complexes is the very strong band in the infrared spectrum near 830 cm’ due to the asymmetric stretch ofthe O=Os Ogroup (5). I also wish to reemphasize our previous (6) caveat with regard to the interpretation of 4f ESCA data for osmium species: the binding energies for the various oxidation states are very close, and strongly influenced by ligands. Battistoni et al. (7) have shown identical binding energies for an osmium l1) and an osmium III) species, for example. The previous data of White et al. (8) show a near overlap in 4fbinding energies between several osmium oxidation states as well as a variation of 0.6 eV within a single oxidation state. The present data ofWhite et al. ( 1), properly interpreted, reemphasize this point, since the 4f /2 binding energy of 52.2 eV for the phenanthroline complex is about I eV lower than those for previously reported osmium (VI) complexes. ESCA data alone are insufficient to characterize osmium oxidation states. E.J. BEHRMAN Department of Biochemistry The Ohio State University Columbus, Ohio 43210 Literature Cited