Oxides of Mn, Re

Mn oxides are typical Bertholide compounds. For example, the stoichimetry, x, of Mn02-jr varies from 0 to 0.3, and several structures are known. These Mn02-jt s are prepared in various ways, e.g. chemical or electrochemical oxidation, hydrolysis and thermal decomposition of Mn salts. 

Mn02 - X are generally active cattilysts for oxidation reactions and also active electrode materials for dry cells. Probably due to the high oxidation activity, very few studies have been reported for acid-base properties and catalysis of Mn oxides. Mn02 has been claimed to be efficient for the hydration of nitriles to amides, in which the acidic character of the catalyst seems to play some role. In the case of hydration of acrylonitrile in aqueous solution, a relationship between the equi acid-base point (EABP) of met ll oxides and catalytic function has been suggested. Mn02 (EABP = 3,7) was active and selective for the formation of amide in acidic solution, and MnO (EABP = 11.2) was active in basic solution, but caused more hydration of the C = C bond. 

The oxidation states of Re in oxides vary from 2 to 7 and are sensitive to the atmosphere. Among them Re(IV) and Re(VII) are stable. Re207 is prepared by oxidation of Re metal or low valent oxides by nitric acid followed by evaporation to dryness. 

Isomerization of 1-butene was studied over crystalline ReOs and Rc207 which were prepared in several ways, and the presence of two different sites were indicated one was sensitively promoted by the presence of H2 and the other (possibly Lewis sites) not.  

Sugiyama, H. Miura, H. Sekiwa, T. Matsuda, Catal. Symp. Catal. Soc. Jpn., 3S08, Kanazawa, 1985. 

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