Polymorphic structures manganese

The structure of a-Mn02 (hoUandites) and selected other common polymorphs of manganese dioxide f)-Mn02 (p)irolusite) and y-Mn02 (ramsdellite). 

No binary xanthate structures of manganese, technetium, or rhenium have been reported. Indeed, there are relatively few crystal structures known with only a single manganese structure (two polymorphs), two phosphine adducts of technetium and three structures containing rhenium, two of which are dinuclear. 

When subjected to high temperatures and pressures, polymorphs have been prepared for some of the difluorides. These all have distorted variants of the fluorite structure, with cubic, or pseudocubic, tetragonal cells. Manganese difluoride has been most studied (28-30) and similar polymorphism reported for cobalt and zinc difluorides (30). Recently, palladium and silver difluorides have been shown to behave in a similar way forming cubic metastable phases (31). In all cases there is a decrease in volume for the structure change. 

Manganese(IV) oxide is polymorphic and often markedly non-stoichiometric. Only the high-temperature P-form has the stoichiometry Mn02 and adopts the rutile structure Figure 5.21). It acts as an oxidizing agent when heated with concentrated acids (e.g. reaction 21.51). 

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