Rare oxides

Genuine iron(V) is a very rare oxidation state. In the preparation of iron oxides (and of other solid-state materials), the intended iron(V) disproportionates mostly into an iron(lll) fraction and two parts of an iron(Vl) fraction [276]. The only example of an iron(V) oxide for which the Mbssbauer parameters are known [185] is La2Li-FeOs- A low isomer shift of = —0.41 mm s was observed at room temperature with practically zero quadmpole splitting [277], which was taken as a proof that iron is accommodated in octahedral FeOg sites surrounded by six Li ions. Although repeatedly cited, it seems that the spectra have never been published, and the data must therefore be considered with care. 

The M+ ions of groups 3 (IIIB), 4 (IVB), and 5 (VB) often react with oxygen containing molecules to form [MO]+. Bare metal ions (M+) are in a relatively rare oxidation state and so there are limited comparisons with condensed-phase... 

The oxide terbium peroxide has a unique formula and exhibits a very rare oxidation state for terbium that is not a whole number. It is one of the rare cases in which the valence is not a whole integer 4Te + 70 —> Tb O ... 

Molybdenum(III) is a relatively rare oxidation state and is easily oxidized to more stable states by air and other mild oxidants. However, recent work has shown the existence of many Mo111... 

Palladium(IV) is a relatively rare oxidation state. The paucity of isolated complexes in comparison with PtIV has been ascribed to the much higher ionization potential required to produce Pd4+ (109.5 us. 97.16 eV for PtIV).303 Binary complexes with oxide and the chal-cogenides have been well characterized as have PdF4 and [PdXe]2- (X = F, Cl, Br). The chemistry of platinum group metals in higher oxidation states has been the subject of a recent review.304... 

By means of complexation, a metal can occur in normally unknown or rare oxidation states. For instance, Co31, being a strong oxidizing agent, is normally not stable in aqueous solutions, but it is stable as Co(NH3)63+. Furthermore, complexation can prevent disproportionation, as in the case of Cu+ e.g., which converts into Cu2+ and Cu(s) in an aqueous solution, although it is stable as Cu(NH3)2+. 

The salt K2[Os(PF3)4] constitutes the most unequivocal instance in which osmium attains this rare oxidation state (it may always be argued for Os(NO)2(PPh3)2, which has been crystallographically characterized, that — II is only a formal oxidation state). The salt is made from Os(PF3)4H2 and potassium amalgam in ether. It is colourless, and the HNMR and IR spectra are consistent with a symmetrical, presumably tetrahedral, structure.432... 

These are among the best characterized compounds in this somewhat rare oxidation state, although they do tend to be unstable (see the preparation of UCle) and UI5 does not exist. 

These metals prefer 18e to 16e. The 16e configuration is more often seen, but 18e complexes are common. A rare oxidation state. 

A remarkable photocatalyst in Table 1 is Rh-doped SrTiOs [19]. It is one of the rare oxide photocatalysts that can produce H2 under visible tight irradiation. The visible tight response is due to the transition from an electron donor level consisting of Rh 4d orbitals to the conduction band of STi03 as shown in Fig. 1. This photocatalyst shows the highest activity when the doping amount is ca. 1%. The amount of 1% is not small as a doping level. The Rh dopant forms a discrete level or a mini band. 

Photcsynthetic plants rarely oxidize amino acids for energy purpose. Instead they convert CO2 and H2O into carbohydrates that are mainly used as energy source. 

Ground-state oxygen alone rarely oxidizes organic compounds. A classical example is the autoxidation of benzaldehyde to benzoic acid, a usually undesirable reaction that takes place even in the absence of light. Other examples of autoxidation without illumination are oxidations at the a positions with respect to aromatic rings or at tertiary carbons [47, 48, 49, 50] and the formation of alkyl hydroperoxides from alkyl dichloroboranes [57]. Some oxidations take place when a compound is treated with oxygen in the presence of bases [9, 52, 53]. 

Whereas internal acetylenes are oxidized to a-diketones, terminal acetylenes give carboxylic acids with one less carbon on treatment with thallium trinitrate [413], potassium permanganate [843], iodosobenzene with tris(triphenylphosphine)ruthenium dichloride as a catalyst [787], or a rather rare oxidant, pentafluoroiodobenzene bis(trifluoroacetate) [797] (equation 144). 

Rhodium(lI).—This relatively rare oxidation state is attracting increasing attention, with the isolation and characterization of several new complexes. 

Magnetite FejOd 0.31 0.00 495 Rare oxidation product or process... 

Retrosynthetically, a synthesis of 271 was envisaged from 273 based on a rare oxidative ring contraction to form the four-membered ring. Dehydrogenation of the... 

Under vigorous conditions strong oxidizing agents such as chromic acid and permanganate attack alkanes, but the reaction is of little synthetic use for usually mixtures of products are obtained in low yield. The reaction was traditionally used in the Kuhn-Roth estimation of the number of methyl groups in an unknown compound. This depends on the fact that a methyl group is rarely oxidized (the relative rates of oxidation of primary, secondary and tertiary C—H bonds are 1 110 7000) and hence the amount of ethanoic acid formed can be quantified. 

Note Jones reagent is a solution of chromium trioxide or potassium dichromate in dilute sulfuric acid and acetone. Acetone markedly affects the properties of chromic acid. Oxidation is very rapid, usually exothermic, and the yields are typically high. This reagent rarely oxidizes unsaturated bonds. 

Oxidation resistance at Poor, except for rare Oxides excellent, SiC -... 

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