Manganese tetravalent

Oxidation of manganese dioxide to higher valence states takes place in the fusion process of Mn02 and KOH. A tetravalent manganese salt identified as K MnO [12142-27-7] (63) which disproportionates spontaneously is formed. 

Tetrathiafulvalene (TTF), 23 707 electrochromic material, 6 581, 581t polymers of, 23 708-709 Tetrathiomolybdate ion, 17 22-23 Tetravalent lead, 14 783 Tetravalent manganese compounds,... 

This two-point measurement technique is used in the system reported by Wicker-sheim and Sun,(27) where a lamp phosphor, tetravalent manganese-activated magnesium fluorogermanate, mentioned above, is used as fluorescent sensor. The excitation... 

Figure 11.5. Excitation and emission spectra of magnesium fluorogermanate activated with tetravalent manganese.

Another example is the balanced integration method described by Sun.(29) This technique is designed to achieve 0.01°C resolution using tetravalent manganese-activated magnesium fluorogermanate, the same sensor material that has been used... 

The nodules are formed by the oxidation and precipitation of iron and manganese. The oxidation of Mn24 is catalyzed by a reaction surface io a tetravalent state that absorbs additional Fe2+ or Mn2+ which, in turn, becomes oxidized. A surface is required and the initial deposition may be of iron oxide, possibly from volcanic or geothermal sources. Proper conditions of pH, redox potential, and metal ion concentration are found in deep ocean waters. The rate of accumulation appears to be very slow. The growth also may be discontinuous, and is estimated at a faster rater rate near the continental margins. 

Figure 11.9 Molecular orbital energy level diagrams computed for tetravalent manganese. (a) Tetrahedral [MnOJ-4 cluster, (b) octahedral [MnOJ-8 cluster (based on Sherman, 1984).

Potter, R. M. and G. R. Rossman. 1979a. The tetravalent manganese oxides Identification, hydration, and structural relationship by infrared spectroscopy. Am. Miner. 64 1199-1218. 

Other than in prokaryotic cells which lack mitochondria and chloroplasts, manganese superoxide dismutases are apparently restricted to the above two organelles in eukaryotic cells (51, 52) this forms strong support for the symbiotic hypothesis for the origin of mitochondria and chloroplasts (53, 54). Kinetic studies of superoxide dismutation by these enzymes indicate three oxidation states of Mn (presumably divalent, trivalent, and tetravalent) are involved in the catalytic cycle (57, 58). They also show that a Mn-02 complex may conceivably be formed. Well-characterized Mn-dioxygen (i.e., 02,02 , 022 ) adducts are extremely rare, the first structurally characterized example being reported only in 1987 (60). 

Orthopyroxene partitions nickel, cobalt, and manganese less than olivine and there are no clear correlations amongst these elements. Although low in abundance, orthopyroxene can be a significant reservoir for the trivalent cations vanadium, scandium plus tetravalent titanium, due to its high modal abundance, especially in depleted xenoliths with little or... 

Potter, R.M. (1979) The tetravalent manganese oxides clarification of their structural variations and relationships and characterization of their occurrence in the terrestrial weathering environment as desert varnish and other manganese oxides. PhD dissertation, Earth and Planetary Science, California Institute of Technology, Pasadena. 

Potter, R.M. Rossman, G.R. (1979c) The tetravalent manganese oxides identification, hydration, and structural relationships by infrared spectroscopy. American Mineralogist M, 1199-1218. 

Tetravalent manganese is not soluble in acids it must be reduced to the divalent state in order to dissolve. Hydrochloric acid is a useful reductant for this purpose, and in the process, a stoichiometric amount of chloride is oxidized to chlorine gas. The evolution of this gas is indicative of the redox nature of the reaction. 

The results of catalytic epoxidation of various olefins, using f-BuOOH as the terminal oxidant and Mn(Me2EBC)Cl2 as the catalyst, are summarized in Table 3.4. The color of the reaction mixture turns to purple upon addition of f-BuOOH and the ultraviolet-visible spectrophotometry shows that the manganese is present predominantly in the tetravalent state, and no dioxygen evolution was observed. 

Pt is also significantly enriched in Co-rich cmsts (Heinetal. 1988,1997 Halbach etal. 1989). However, the mechanism of enrichment in the cmsts is not well understood. Hodge et al. (1985) argued that Pt is oxidized from the PtCb state in seawater to the tetravalent state in manganese nodules. This process was thought to be responsible for the anomalously high Pt/Pd ratios in nodules (50-1,000) compared to seawater (4.5). However, Halbach et al. (1989) considered that this process would not be possible... 

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