V oxide systems

The neodymium oxide-vanadium(v) oxide and samarium oxide-vanadium(v) oxide systems have been investigated by thermal, i.r., and X-ray techniques. " Potassium neodymium double fluorides formed in the KF-Ndp3 system have been investigated by X-ray diffraction procedures. Formation of structures with statistical distributions of metal atoms at cationic positions was reported to be characteristic of the KF-Ndp3 system. The equilibrium diagram of the Al203-Nd203-Sr0... 

Pyridine V-oxides have also received attention due to their catalytic properties, for example, they have been used as Lewis bases in aldol reactions <05JOC5235, 05SL2388>. Maikov and co-workers elaborated on the use of pyridine V-oxides as a catalyst for allylation of aldehydes with allyltrichlorosilanes <05OL3219>. Additionally, Higuchi et al. report a highly reactive Ru porphyrin/pyridine V-oxide system that shows unique reactivity for the oxidation of various... 

Semiconducting glasses exhibit electronic rather than ionic conductivity. Glasses with resistivities in the range of 10 to 10 ohm-cm have been reported in the Ge-P-V oxide system and in the elemental glasses of either S, Se, or Te combined with one or more of the elements Si, Ge, P, As, Th, and Pb. Electronic devices are described that use semiconducting glasses as the solid-state switch or memory component. ... 

Sinn C. 1999. Dynamic light scattering by rodlike particles Examination of the vanadium (V)-oxide system. Eur. Phys. J.B1 599-605. 

Phosphoric acids and the phosphates maybe defined as derivatives of phosphoms oxides where the phosphoms atom is in the +5 oxidation state. These are compounds formed in the M2O—P20 system, where M represents one cation equivalent, eg, H", Na", 0.5 Ca ", etc. The molecular formula of the phosphoms(V) oxide [1314-56-3] is actually P O q, but this oxide is commonly referred to in terms of its empirical formula, P2O5. StmcturaHy, four phosphoms—oxygen (P—O) linkages are arranged in an approximate tetrahedral configuration about the phosphoms atom in the phosphate anion. Compounds containing discrete, monomeric PO ions are known as orthophosphates or simply as phosphates. 

Cyclic hydroxamic acids and V-hydroxyimides are sufficiently acidic to be (9-methylated with diazomethane, although caution is necessary because complex secondary reactions may occur. N-Hydroxyisatin (105) reacted with diazomethane in acetone to give the products of ring expansion and further methylation (131, R = H or CH3). The benzalphthalimidine system (132) could not be methylated satisfactorily with diazomethane, but the V-methoxy compound was readil3 obtained by alkylation with methyl iodide and potassium carbonate in acetone. In the pyridine series, 1-benzyl-oxy and l-allyloxy-2-pyridones were formed by thermal isomeriza-tion of the corresponding 2-alkyloxypyridine V-oxides at 100°. 

As indicated above, when a positive direct current is impressed upon a piece of titanium immersed in an electrolyte, the consequent rise in potential induces the formation of a protective surface film, which is resistant to passage of any further appreciable quantity of current into the electrolyte. The upper potential limit that can be attained without breakdown of the surface film will depend upon the nature of the electrolyte. Thus, in strong sulphuric acid the metal/oxide system will sustain voltages of between 80 and 100 V before a spark-type dielectric rupture ensues, while in sodium chloride solutions or in sea water film rupture takes place when the voltage across the oxide film reaches a value of about 12 to 14 V. Above the critical voltage, anodic dissolution takes place at weak spots in the surface film and appreciable current passes into the electrolyte, presumably by an initial mechanism involving the formation of soluble titanium ions. 

In cyclic systems, conformational effects and the requirement for a cyclic TS determine the product composition. This effect can be seen in the product ratios from pyrolysis of /V,/V-dimethyl-2-phcnylcyclohexylaminc-/V-oxide. 

We refrain here from giving an extensive overview of studies on the surface structure of vanadium oxide nanolayers, as this has already been done for up to year 2003 in our recent review [97]. Instead, we would like to focus on prototypical examples, selected from the V-oxide-Rh(l 1 1) phase diagram, which demonstrate the power of STM measurements, when combined with state-of-the-art DFT calculations, to resolve complex oxide nanostructures. Other examples will highlight the usefulness of combining STM and STS data on a local scale, as well as data from STM measurements, and sample area-averaging spectroscopic techniques, such as XPS and NEXAFS, to derive as complete a picture as possible of the investigated system. 

EXAMPLE 13.13. Name the following according to the Stock system (a) FeCl, (6) U02S04, and (c) P4O10. (a) Iron(II) chloride, (b) dioxouranium(VI) sulfate, and (c) phosphorus(V) oxide. 

The effect of inorganic additives upon ignition delay in anilinium nitrate-red finning nitric acid systems was examined. The insoluble compounds copper(I) chloride, potassium permanganate, sodium pentacyanonitrosylferrate and vanadium(V) oxide were moderately effective promoters, while the soluble ammonium or sodium metavanadates were very effective, producing vigorous ignition. 

The effects of various metal oxides and salts which promote ignition of amine-red fuming nitric acid systems were examined. Among soluble catalysts, copperQ oxide, ammonium metavanadate, sodium metavanadate, iron(III) chloride (and potassium hexacyanoferrate(II) with o-toluidine) are most effective. Of the insoluble materials, copper(II) oxide, iron(III) oxide, vanadium(V) oxide, potassium chromate, potassium dichromate, potassium hexacyanoferrate(III) and sodium pentacyanonitrosylferrate(II) were effective. 

For the 4d series the M(V) oxidation state is found for Mo, Tc, and Ru as hexafluoro anions. These MFe complexes are all quite strongly oxidising, and their stability again decreases towards the end of the series. Some spectroscopic data are available for all three systems and are reviewed below. 

Structural Imperfections. In many respects HREM has had a greater impact upon our knowledge of the nature of the atomic reorganization at crystalline imperfections than any other single technique. One of the very first contributions of HREM as a new analytical and structural tool was described in the paper by Iijimia (42) in 1971 on 2 10 29 v -ewe< down to its b - axis. Structural faults, arising from subtle fluctuations in composition, could be clearly seen in the block-structure (based on NbO octahedra) which is a feature of this ternary oxide system. More than a decade later similar materials are yielding to active scrutiny by HREM, and Horiuchi (43), for example, has shown how point defects may be directly viewed... 

A synthetic route to the fused 1,2,3-triazole 2-oxide systems 151 via intramolecular cyclization of (V-nitroso and azido groups on the base 1,2,5-oxodiazoles has been described (Scheme 39) <1996TL8577>. 

In conclusion I should like to consider a few of the chemical investigations which might be accomplished in the rare earth field by Mossbauer spectroscopy. The study of nonstoichiometric oxides has been discussed earlier, but there is the problem of finding an appropriate doping nuclide for the praseodymium oxide system. The element most capable of following the changes in oxidation state of the praseodymium is terbium-159, which does have a Mossbauer state, however, with a rather broad resonance (58,0 k.e.v., = 0.13 nsec.). Nevertheless, with a sufiiciently... 

Anodic conversion of aromatics proceeds in most cases by le-transfer to the anode to form a radical cation (34) (Scheme 9). Oxidation is facilitated by extension of the 7T-system ( 1/2 vs. Ag/Ag+ benzene 2.08 V, pyrene 0.86 V) and by electron donating substituents ( 1/2 vs. Ag/Ag+p-phenylenediamine —0.15 V). Oxidation potentials of polycyclic aromatics and substituted benzenes are collected in Ref [140-142]. 

Levitskii V. A., Golovanova Yu. G., Popov S. G., and Chentsov V. N. (1975). Thermodynamics of binary oxide system Thermodynamic properties of nickel orthosilicate. Russ. J. Phys. Chem., 49 971-974. 

Nitriloacetic acid reacts with vanadium-(m). -(iv), or -(v) oxides to form oxovanadatranetrionic acid (38). The crystal structure of [VO(CjQHgNO)2] (CjgHgNOH = 2-methyl-8-quinolinol) has shown that the vanadium atom has a five-co-ordinate trigonal-bipyramidal environment, with three oxygen atoms in the equatorial plane and the two nitrogen atoms of the bidentate ligand in the apical positions. The optimum conditions for the formation of a 1 2 2 vanadium(iv)-morin-4-aminoantipyrine system have been described as pH 5, a tenfold excess of morin (39), and a 3300-fold excess of 4-amino-antipyrine. ... 

The kinetics and mechanism for oxygen transfer between 4-cyano-V,V,-dimethylaniline V-oxide and a C2-capped mexo-tetraphenylporphyrinatoiron(III) and mc5 o-tetrakis(pentafiuorophenyl)-porphyrinatoiron(III) have been established. Addition of a copper(II) porphyrin cap to an iron(II)-porphyrin complex has the expected effect of reducing both the affinities and rate constants for addition of dioxygen or carbon monoxide. These systems were studied for tetradecyl-substituted derivatives solubilized by surfactants such as poly(ethylene oxide) octaphenyl ether. ... 

For instance, the relative oxidizing ability of Ar3BiCl2 (in the Ar3BiCl2/DBU system) was found to be in the order Ar = /j-nitrophenyl > /j-(trifluoromethyl) phenyl > o-methyl-p-chlorophenyl > p-chlorophenyl > o-methylphenyl > phenyl > p-methylphenyl. On the basis of these findings, new efficient triarylbismuth(V) oxidants have been prepared and some reagents are now commercially available. 

Feltz, A. Martin, A. (1987) Solid-state reactivity and mechanisms in oxide systems. 11 Inhibition of zinc ferrite formation in zinc oxide - a-iron(lll) oxide mixtures with a large excess of a-iron(lll) oxide. In Schwab, G.M. (ed.) Reactivity of solids. Elsevier, 2 307—313 Fendorf, S. Fendorf, M. (1996) Sorption mechanisms of lanthanum on oxide minerals. Clays Clay Miner. 44 220-227 Fendorf, S.E. Sparks, D.L. (1996) X-ray absorption fine structure spectroscopy. In Methods of Soil Analysis. Part 3 Chemical Methods. Soil Sd. Soc. Am., 377-416 Fendorf, S.E. Eick, M.J. Grossl, P. Sparks, D.L. (1997) Arsenate and chromate retention mechanisms on goethite. 1. Surface structure. Environ. Sci. Techn. 31 315-320 Fendorf, S.E. Li,V. Gunter, M.E. (1996) Micromorphologies and stabilities of chromiu-m(III) surface precipitates elucidated by scanning force microscopy. Soil Sci. Soc. Am. J. 60 99-106... 

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