Transition metals and oxides

Colored or stained glass has been made for thousands of years, first by Egyptians and later by Romans. Color is typically introduced by addition of transition metals and oxides. Table 12.5 contains selected inorganic colorants and the resulting colors. Because of the high... 

Nonempirical GGA functionals satisfy the uniform density limit. In addition, they satisfy several known, exact properties of the exchange-correlation hole. Two widely used nonempirical functionals that satisfy these properties are the Perdew-Wang 91 (PW91) functional and the Perdew-Burke-Ernzerhof (PBE) functional. Because GGA functionals include more physical ingredients than the LDA functional, it is often assumed that nonempirical GGA functionals should be more accurate than the LDA. This is quite often true, but there are exceptions. One example is in the calculation of the surface energy of transition metals and oxides. 

W15. Wolff, S. P., Diabetes mellitus and free radicals. Free radicals, transition metals and oxidative stress in the aetiology of diabetes mellitus and complications. Br. Med. Bull. 49, 642-652 (1993). 

Ghio AJ, Stonehuerner J, Pritchard RJ, Pian-TADOSi CA, Quigley DR, Dreher KL and Costa DL (1996) Humic-like substances in air pollution particulates corrdate with concentrations of transition metals and oxidant generation. Inhal Toxicol 8 479-494. 

Krylov, O. V. Kiselev, V. F. "Adsorption and Catalysis on Transition Metals and Oxides Thereof" Khimia Moscow, 1981. 

Of oxy-organic compounds (e.g., ethanol - acetaldehyde) Copper (generally transition metals and oxides Group IB metals for first three reactions)... 

Clearly, the scope of oxidation by this method is quite wide because innumerable combinations of metals (including practically all transition metals) and oxidants are possible,... 

Two major subsets of polyoxometalates are the isopolyoxometalates (or isopolyanions) which contain only transition metal and oxide ions, and the heteropolyoxometalates (or heteropolyanions) which contain one or more "heteroatoms" in addition to the transition metal and oxide ions. The heteroatom in polyoxometalates can be one of many elements in the p or d blocks. In this review we have highlighted the photochemistry of two polyoxometalates, dodecatungstophosphate, a representative heteropolyanion of the common Keggin structure, and decatungstate, a representative isopolyanion, whose structures are given in Figure 1. 

A key advantage of CNTs and CNFs is the possibility to functionalize or dope their surface with various elements to improve the dispersion of the inorganic active phase or introduce new organic active sites for performing subsequent catalytic reactions. Chemical functionalization of CNTs and/or CNFs is critically important for developing new, highly efficient, carbon-based materials for downstream catalytic applications. It is expected that doped CNTs could represent an important class of new metal-free catalysts with better catalytic performance and improved resistance toward deactivation compared with traditional supported transition metals and oxides. 

Manganese is the third most abundant transition metal, and is widely distributed in the earth s crust. The most important ore is pyrolusite, manganese(IV) oxide. Reduction of this ore by heating with aluminium gives an explosive reaction, and the oxide Mn304 must be used to obtain the metal. The latter is purified by distillation in vacuo just above its melting point (1517 K) the pure metal can also he obtained by electrolysis of aqueous manganese(II) sulphate. 

Phosphite triesters, P(OR)3, form donor complexes with transition metals and other acceptors and are oxidized to the respective phosphates under appropriate conditions. 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

Unlike nitric oxide, NO, the monomeric radical sulfur nitride, NS, is only known as a short-lived intermediate in the gas phase. Nevertheless the properties of this important diatomic molecule have been thoroughly investigated by a variety of spectroscopic and other physical techniques (Section 5.2.1). The NS molecule is stabilized by coordination to a transition metal and a large number of complexes, primarily with metals from Groups 6, 7, 8 and 9, are known. Several detailed reviews of the topic have been published. ... 

For all three halates (in the absence of disproportionation) the preferred mode of decomposition depends, again, on both thermodynamic and kinetic considerations. Oxide formation tends to be favoured by the presence of a strongly polarizing cation (e.g. magnesium, transition-metal and lanthanide halates), whereas halide formation is observed for alkali-metal, alkaline- earth and silver halates. 

The ultimate purpose of mechanistic considerations is the understanding of the detailed reaction pathway. In this connection it is important to know the structure of the active catalyst and, closely connected with this, the function of the cocatalyst. Two possibilities for the action of the cocatalyst will be taken into consideration, namely, the change in the oxidation state of the transition metal and the creation of vacant sites. In the following, a few catalyst systems will be considered in more detail. 

Colona and coworkers oxidized a variety of alkyl aryl and heterocyclic sulfides to the sulfoxides using t-butyl hydroperoxide and a catalytic amount of a complex (97) derived from a transition metal and the imines of L-amino acids. Of the metals (M = TiO, Mo02, VO, Cu, Co, Fe), titanium gave the highest e.e. (21%), but molybdenum was the most efficient catalyst. The sulfoxides were accompanied by considerable sulfone125. 

There are many transition metal ion oxidants used in organic chemistry for the interconversion of functional groups. Those which have been used for the preparation of sulphones from sulphoxides will be discussed below. It is very interesting to note that this type of oxidant often reacts more rapidly with sulphoxides than with sulphides and so sulphoxides may be selectively oxidized with transition metal ion oxidants in the presence of sulphides. This is in direct contrast to the oxidation of sulphides and sulphoxides with peracids and periodate, for example, where the rate of reaction of the sulphide is more than 100 times that for the corresponding sulphoxide. 

Step 1 Identify the cation and the anion (see Table D.l or Appendix 3A, if necessary). To determine the oxidation number of the cation, decide what cation charge is required to cancel the total negative charge of the anions. Step 2 Name the cation. If the metal can have more than one oxidation number (most transition metals and some metals in Groups 12 through 15/V), give its charge as a Roman numeral. 

One of the distinctive aspects of transition-metal and lanthanide chemistry is cluster formation via metal-metal bonding that is characteristic of many of these elements in low oxidation states [1]. The unique structural, chemical, and... 

Investigations of the interaction between 3d transition metals and octahedral halide or oxide metal clusters led to the preparation of a number of novel cluster compounds such as the series AxByNbgClig (A = Li, K, Rb, Cs B=Ti, V, Mn, Cu) [33], and TizNbgOu [34]. 

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