Metal superoxides

However, under anhydrous conditions and in the absence of catalytic impurities such as transition metal ions, solutions can be stored for several days with only a few per cent decomposition. Some reductions occur without bond cleavage as in the formation of alkali metal superoxides and peroxide (p. 84). 

Whether the ion pair [(C6H5)2CO 02 "] separates to yield alkali metal superoxide (M02) or collapses to yield alkali metal peroxide (M202) depends upon the stability of the alkali metal superoxide. Thus, in general the yield of superoxide increases as the alkali metal is changed from lithium to sodium to potassium to rubidium, a sequence that parallels the stabilities of the superoxides. Superior yields of superoxides are observed in pyridine solution (Table XI). This is apparently connected with the ability of pyridine to stabilize the superoxide ion by complex formation (25). 

The reactions of transition metal superoxides with reducing and oxidizing metal complexes have been summarized (58) and will not be discussed here. 

These solutions of electrons are not mere laboratory curiosities. In addition to being strong bases, they are also good one-electron reducing agents. For example, pure samples of alkali metal superoxides may be readily prepared in these solutions ... 

Oxidation of an alkali metal dissolved in liquid ammonia with oxygen. All the alkali metal superoxides have been prepared by this method. Although lithium superoxide (LiO ) has not been isolated in a room temperature-stable form, it has been demonstrated that when lithium is oxidized in liquid ammonia at —78°C the superoxide does form and is stable at that temperature. 

The metal peroxides contain the peroxide ion, 022-, and the metal superoxides contain the superoxide ion, 02- ... 

When metal superoxides, such as K02, dissolve in water, they decompose with evolution of oxygen ... 

The lattice energies of the alkali metal superoxides have been calculated by Evans and Uri (35) and by Kazarnovskii (71). Evans and Uri,... 

The Lattice Energies (kcal/mole) op the Aekau Metal Superoxides... 

The name superoxide was introduced in 1934 to signify an exceptional degree of reactivity of superoxide radical anion in KO2 [I87J. It was obtained by acting with dioxygen on metals such as potassium (and Rb, C5). It is marked by nuclcopliilicity. In aprotic media it reacts rapidly with primary and secondary alky halides to yield dialkyl peroxide and with acyl chlorides to yield diacyl peroxides. Superoxides arc reduced to peroxides under some experimental conditions. They were recently reviewed by Sawyer and Valentine [188]. No explosive properties of metal superoxides or their mixtures have been recorded. 

Metal superoxides, (L)M(n + (C - ), are most commonly prepared from (L)M" + and 02. These dioxygen adducts are rarely stable, and normally undergo subsequent reactions (formation of p-peroxo dimers is the most common decomposition pathway). Alternatively, direct reactions with inorganic superoxide (e.g., K02) may yield superoxo complexes ... 

Table 6 I.r. and Raman (R) data for alkali-metal superoxides iwave-numberslcar )...

According to [99], the formation of active intermediate metal-containing particles within i fuel-deficient flame occurs as a result of the direct oxidation of alkali metals, and the metal superoxide is formed ... 

It was assumes that metal superoxides react easily with the active centers of a combustion process, forming more stable and active compounds [99],... 

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