Abstract: Photoelectron spectroscopic investigations (XPS) of the spinels NiMn2O4 and MzNiMn2−zO4 (M = Li, Cu) in comparison with Mn2TiO4, ZnMn2O4, and MgNiMnO4, containing Mn in only one oxidation state, show that in the former compounds MnII, MnIII, and MnIV are present. By a fitting process yielding the amounts of the Mn ions in the different oxidation states it is possible to determine the cation distribution of NiMn2O4 which is characterized by a high inversion parameter and a considerable degree of disproportionation. Cation valencies and their distribution in the substituted spinels are discussed. An increasing concentration of MnIV with higher values of z is reflected in the spectra by shift of the Mn p signals and by changes in their shape.

Abstract: A process is described for the preparation of a manganese complex catalyst having formula (1) wherein Mn is manganese in a III or IV oxidation state; each X is independently a coordinating or bridging species; L is an organic ligand containing at least two nitrogen atoms that coordinate with the Mn; z is an integer ranging from -4 to +4; Y is a monovalent or multivalent counterion leading to charge neutrality; and q is an integer from 1 to 4. The process comprises two steps. In the first step a manganese (II) salt is reacted with the ligand L or precursor thereof in the presence of a counterion salt MzYq, where M is selected from metallic, ammonium and alkanolammonium ions. The resulting manganese coordinated substance is reacted with an oxidising agent at a pH of at least 12. The manganese complex catalyst is an active bleach catalyst.

Abstract: The semisynthetic selenoenzyme selenosubtilisin catalyzes the reduction of alkyl hydroperoxides with concomitant oxidation of 3-carboxy-4-nitrobenzenethiol. To gain insight into the mechanism of this process, three oxidation states of the enzyme that are relevant to the redox cycle have been characterized by 77 Se NMR spectroscopy. Oxidation of selenosubtilsin with hydrogen peroxide in the absence of thiol yields a species whose spectrum consists of two peaks at 1188 and 1190 ppm, consistent with the selenium prosthetic group being in the seleninic acid oxidation state

Abstract: Polymerization of ring-strained cyclic olefins takes place in the presence of a one-part or two-part catalyst which is air and moisture stable and which comprises a transition metal-containing compound. The one-part transition metal-containing catalyst is selected from the group consisting of (a) compounds of the formula: (L1) (L2)Q wherein Q represents Mo or W; L1 represents one to six CO (carbonyl) ligands; L2 represents none to 5 ligands, each of which is a non-ionic compound or unit of a polymer which can be the same or different, each contributes two, four, or six electrons to the metal and is different from L1; wherein the sum of the valence electrons of Q and the electrons contributed by the ligands L?1 and L2? is 18, (b) at least one of cationic ruthenium and osmium-containing organometallic salts having at least one polyene ligand, and (c) [Ir(RO?2?CHC=CHCO2R)2Cl]2 wherein each R independently is hydrogen or lower alkyl (C1 to C4), provided that the oxidation state of the metal is in the range of +3 to 0, and that cocatalysts containing C-halogen bonds are not present. The two-part catalyst comprises (a) a transition metal-containing catalyst, provided that the oxidation state of the transition metal is in the range of +3 to 0, and (b) a cocatalyst selected from the group consisting of (i) terminal or silyl alkynes, (ii) organosilanes containing at least one of α and β groups, (iii) oxidative salts or oxidative compounds containing an oxygen atom to non-oxygen atom double bond, and (iv) heteroatom-containing alkenes. The polymerized composition is useful to provide molded articles, elastomers, dielectric supports, ionophoric or biologically active materials, composite materials, and the like.

Abstract: The known crystal structures of co-ordination compounds containing o-benzoquinone, tetrachloro-o-benzoquinone and 3,5-di-tert-butyl-o-benzoquinone derivatives in the form of catecholates I, semiquinonates II or benzoquinones III have been examined. Since forms I–III differ both in oxidation state and structural features, a simple method is proposed to correlate the oxidation states of these ligands with their structural parameters, thus allowing the determination of the oxidation state on the basis of crystallographic data. By this procedure it is possible to confirm that the o-benzoquinone complexes in most cases assume charge-localized electronic structures, and the same conclusion is reached by factor analysis. The results are compared with literature oxidation-state assignments, and the periodic trend in the charge distribution across a transition series is discussed for homoleptic complexes.

Abstract: The present review deals with the anomalous stabilisation of the oxidation state 2+ of a number of lanthanides and actinides. This stabilisation of the oxidation state 2+ is due to the lowering of the energy of a d-orbital as a result of crystal field splitting in the ligand field and d-electron participation in chemical bonding. The bibliography includes 68 references.

Abstract: X-ray photoelectron spectroscopy (XPS) has been applied to the study of the oxidation state variations of Cr ions in the chromia/zirconia system (CrOx/ZrO2) submitted to redox cycles: O2 at 773 K (standard oxidation), CO at 673 K (standard reduction) and H2O after standard reduction at 743 K. The XPS results are compared with those coming from the average oxidation number determination (n) by redox cycling and with electron spin resonance (ESR) analysis, particularly with regard to the Cr(V) identification. The results show that equilibrium adsorption of chromic acid on zirconia gives Cr(VI) species (binding energy ∼ 580 eV). The XP Cr(VI) feature shows a continuous evolution towards reduced chromium states as the samples age. After oxygen treatment, in addition to Cr(VI), the presence of a component at 1 eV lower binding energy is required to reproduce the spectral feature. This component was assigned to Cr(V) on the basis of ESR and average oxidation state results. Thermal treatment in CO (standard reduction) results in a broad (4.5−5.5 eV) and unresolved Cr 2p feature. The presence of Cr(II) at 576.0 ± 0.2 eV was established by curve fitting procedures. Cr(II) is destroyed by H2O treatment at 743 K, with ensuing formation of Cr(III) species.

Abstract: The chemical nature of the nitrogens in polypyrrole (PPY) and poly(N-methylpyrrole) (PMPY) has been critically compared using X-ray photoelectron spectroscopy as a primary tool. Treatment of PPY/perchlorate complex with NaOH results in a deprotonation process which gives rise to a PPY base (DP-PPY) having an intrinsic oxidation state consisting of 25% oxidized imine-like (=N-) structure, similar to that observed in the 50% oxidized emeraldine state of polyaniline. This intrinsic oxidation state, however, does not exist in the nitrogen-substituted PPY. As a result, the charge-transfer (CT) mechanisms involving the two base polymers and the various oxidants and electron acceptors are vastly different. The PMPY base undergoes strong CT interactions with metal oxidants, such as Cu(ClO4)2, but interacts only weakly with organic electron acceptors, such as the halobenzoquinones and cyanobenzoquinones. The reverse is true for DP-PPY. Both polymer complexes also exhibit different thermal degradation behaviour.

Abstract: Disclosed is a catalyst system for the homopolymerization and copolymerization of alpha-olefins having 2-8 carbon atoms, said catalyst system comprising a cyclopentadienyl Group 6b metal hydrocarbyl compound in which the metal has an oxidation state of +3, said Group 6b metal compound being supported on an inorganic support. The catalyst system may also contain a Group 2 or Group 3 metal alkyl compound.

Abstract: One-electron oxidation of several chromium(III) porphyrins has been studied by steady-state and pulse radiolysis techniques under different conditions. Two types of products are observed: those exhibiting intense broad absorptions at λ 600 nm, ascribed to the π-radical cations, and others exhibiting minor shifts of the porphyrin bands, ascribed to chromium(IV) porphyrins. CrIIIOEP (octaethylporphyrin), CrIIITPP (tetraphenylporphyrin), and CrIIITMP (tetramesitylporphyrin) in CH2Cl2 undergo one-electron oxidation on the ligand to give π-radical cations, which are stable after ligation, and further oxidation gives the dications. In the presence of KOH, however, they form CrIV-porphyrins and further radiolysis gives Crv-porphyrins. CrIIITSPP [tetrakis (4-sulfonatophenyl)porphyrin], CrIIIT3PyP [tetrakis(3-pyridyl)porphyrin], and CrIIIMSP (mesoporphyrin-IX), oxidized in 1 mol dm–3 aqueous HCl, form unstable π-radical cations which decay by disproportionation. The pulse radiolysis results indicate that the initial step in the oxidation of all CrIIIP and OCrIVP species occurs at the porphyrin π-system and that, under certain conditions, the initial π-radical cation may undergo intramolecular electron transfer from the metal centre to the ligand to form the higher oxidation state Cr-porphyrin.

Abstract: Coarse-grain unactivated manganese powder reacts with Me3Pl2 in diethyl ether to form the polymeric [Mn(PMe3)I2]n complex, I, which reacts with trace quantities of dioxygen to form dinuclear [Mn2(PMe3)3I5]·PMe3, II, the first mixed oxidation state (+2/+3) manganese complex which contains phosphine ligands; both I and II react with an excess of dioxygen to form the monomeric [Mn(PMe3)2I3].

Abstract: 15 N solid-state NMR spectra have been recorded on a series of platinum complexes with two different amine ligands, 15 N-enriched 1,2-diaminocthane (en) and natural abundance 3,7-diazanonane-1,9-diamine (2,3,2-tet). The results show that the 15 N chemisel shift and J coupling to 195 Pt are very sensitive to the effective oxidation state of the metal atom and that, in both discrete platinum(II) and platinum(IV) complexes as well as in mixed-valence complexes which can be formed therefrom, the platinum atom environments become more similar on changing from a chloro to a bromo to an iodo species

Abstract: Selenium-modified Rh6(CO) 16/Mg0 catalysts were prepared by the reaction of Rh6(CO)16/Mg0 with (CH3)2Se in order to examine the promoting effect of an electronegative additive on Rh catalysis for ethene hydroformylation. The deposited Se (Se/Rh6 = 0.6) enhanced the rate of propanal formation 1.9 times as compared with the case of an undepited catalyst. The selectivity of the hydroformylation was improved from 20 to 50% by the Se addition. To the contrary, the monotonous suppression of ethane formation by increasing the Se amount was observed. Further doping of Se reduced the hydroformylation activity. TPD, IR, and Se K-edge and Rh K-edge EXAFS revealed that (CH3)2Se reacted with the Rh atoms of partially-decarbonylated Rh, species on the MgO surface, forming Se-Rh bonds at a distance of 0.244 nm. XPS data suggested that the oxidation state of Se in the catalyst is Se-, while Rh is in a nearly metallic state. CO adsorbs on the rhodium atoms bonded to Se, which is contrasted to blocking of the neighboring Rh sites by Se atom observed with usual impregnated Rh catalysts. The structures of the Se-undoped and -doped Rh6 clusters on MgO are presented in relation to the active site of the cluster catalyst. The data indicate an advantage of molecular clusters over impregnated particles in adsorption capability and catalysis.

Abstract: The molecular sieve VAPO-5 has been synthesized hydrothermally in form of large crystals up to 660 μm in length. They have been used as a model substance for the study of vanadium incorporation into the framework. Our results show that vanadium was incorporated into the framework though in relatively small amounts. The results are in agreement with earlier findings for powder preparations of VAPO-5, except for the oxidation state of the vanadium ions and its stability. These conclusions agree with those arrived at previously for vanadium silicate KVS-5.

Abstract: Publisher Summary This chapter discusses structure, preparation, and color of penta-aryl bismuth compounds. Because bismuth penta-aryls are pentacoordinated species, the problem of a trigonal bipyramidal versus a square pyrimadal structure needs to be redescribed. Trigonal bipyramidal and square pyramidal structures are interconvertible–for example, via the Berry pseudorotation. In general, the trigonal bipyramid is considered the principal geometry of a five coordinated species, certainly based on statistics on the hundreds if not thousands of known cases. Wittigs method of preparing BiAr 5 materials in three steps is still useful. There are normally no difficulties in obtaining the BiAr 3 materials. With this general method homoleptic compounds as well as compounds with the composition BiAr 3 Ar 2 ’ are readily prepared. Visible color for a main group compound in its highest oxidation state is a surprising phenomenon. This color is because of a broad absorption, for Bi(C 6 H 5 ) 5 at λ max = 532 nm, that is also weak, log ɛ = 2.4. The color depends on the substitution and the structure.

Abstract: : The polyanilines and their derivatives are a large class of mixed oxidation state polymers which can be synthesized by the oxidative polymerization of the appropriate monomeric aniline. Certain oxidation states of the polymer can be doped to the metallic conducting regime either by aqueous protonic acids or by partial oxidation. The synthesis and key chemical reactions of the intrinsic properties of the doped polymer by stretch-orientation which results in significant increases in conductivity, crystallinity and tensile strength will be described.