Metal ions, in oxidations

Yamazaki, H., Ueng, Y.F., Shimada, T. and Guengerich, F.P. (1995) Roles of divalent metal ions in oxidations catalyzed by recombinant cytochrome P450 3A4 and replacement of NADPH-cytochrome P450 reductase with other flavoproteins, ferredoxin, and oxygen surrogates. Biochemistry, 34, 8380—8389. 

A number of topics have not been tendered the attention due them enzyme processes, catalytic effects of metal ions in oxidation-reduction reactions, and the activation of small molecules such as H2, 02, and H202 by metal ions. This can be justified only by preoccupation with less well explored groups of reactions, which, it is to be hoped, will receive increased attention in future years. 

Table 6.3. Octahedral site preference energies of transition metal ions in oxide structures...

Another manifestation of covalent bonding relates to the sulphide mineralogy of the transition elements. Although earlier chapters have stressed properties of transition metal ions in oxides and silicates, an important feature of these elements is the frequency of their geochemical association with B-sub-group non-metal and metalloid elements such as sulphur, selenium, tellurium, phophorus, arsenic and antimony. The chalcophilic properties of iron, cobalt, nickel and copper in the crust are well known and are important eco-... 

Despite the enormous importance of zeolites (molecular sieves) as catalysts in the petrochemical industry, few studies have been made of the use of zeolites exchanged with transition metal ions in oxidation reactions.6338- 634a-f van Sickle and Prest635 observed large increases in the rates of oxidation of butenes and cyclopentene in the liquid phase at 70°C catalyzed by cobalt-exchanged zeolites. However, the reactions were rather nonselective and led to substantial amounts of nonvolatile and sieve-bound products. Nevertheless, the use of transition metal-exchanged zeolites in oxidation reactions warrants further investigation. 

The authors [100] investigated mechanochemical synthesis of these perovskites using transition oxides in different oxidation state and lanthanum oxide or carbonate as initial compounds. The activated samples were then heated at temperatures above 500°C. The degree of interaction was shown to depend upon the oxidation degree of transition metal ions in oxides. The higher oxidation degree, i.e. the acidity of oxide, is preferable. 

HF In the semiconductor manufacturing process, buffered HE (BHF) and DHF are widely used for the etching of oxide layers and the removal of native oxide. Most polished surfaces will have a thin layer of oxide poly-Si, oxide, W, Cu, and so on. The removal of oxide by DHF could also help to remove metallic ions in oxide. DHF cleaning is also known to be very effective in removing particles trapped in recessed and eroded features. 

Investigations of Highly Dispersed Transition Metal Ions in Oxides or Zeotype-Systems by PL Spectroscopy... 

We arbitrarily define the nrajority of metal ions in oxidation states II and III as being in normal oxidation states, but we do not adhere rigorously to this classification. 

Originally, photoluminescence spectroscopy was applied to characterize the local coordination of metal ions as well as to probe structural perturbations that occur due to alkaline earth and rare earth metal ions in oxides such as silica and alumina. Emphasis has turned to elucidating the mechanisms of catalytic and photocataljTic reactivity, i.e., the characterization, at the molecular level, of the active surface sites as well as the significant role of these sites in catalysis and photocatalysis. 

Tsitovskaya, I. L., Catalytic Properties of Zeolites Containing Transition Metal Ions in Oxidation Reduction Reactions, Dokl. Akad. Nauk SSSR (1971) 196,872. 

In this case, X is a halide, Mt is a transition metal ion in oxidation state z and L is a ligand that is complexed with the metal to impart solubility in the polymerization medium. Numerous transition metals, hahde initiators and ligands can be used to... 

Kinetic studies of molybdenum complexes have continued, and a picture is now available for the relative labilities of molybdenum complexes with the metal ion in oxidation states +3, +4 92,33 +5 34 +5. The nature of molybdenum(iv)... 

H3N)3RuN y V< NRu(NH3)3j Except where otherwise stated, the left-hand metal ion is in oxidation state iii and the right-hand metal ion in oxidation state ii. 

By far the greatest proportion of the sputtered flux has zero charge, i.c.. consists of neutrals. The fraction desorbed as ions is only 10" -10" . The number of sputtered ions per incident primary ion (i.e.. the secondary-ion yield tenns often used in SIMS and SNMS and explained in Section 1.4) can also vary tremendously with the chemical environment in the near-surface layers, a phenomenon known as the matrix effect. Examples of the, secondary-ioii yield enhancement, which in some cases can reach several orders of magnitude, are described in [9, 10] for positive metal ions in oxidic environment.s. 

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