Manganese crystal structure

An additional problem is encountered when the isolated solid is non-stoichiometric. For example, precipitating Mn + as Mn(OH)2, followed by heating to produce the oxide, frequently produces a solid with a stoichiometry of MnO ) where x varies between 1 and 2. In this case the nonstoichiometric product results from the formation of a mixture of several oxides that differ in the oxidation state of manganese. Other nonstoichiometric compounds form as a result of lattice defects in the crystal structure. ... 

Fig. 3. Crystal structure of manganese dioxides where ( ) represent Mn and (° ), and the lines define the octahedra hoUandite (6), psilomelane (7),...

Analysis of the volumetric effects indicates that as a result of such mechanical activation, iron and manganese are concentrated in the extended part of the crystal, while tantalum and niobium are predominantly collected in the compressed part of the distorted crystal structure. It is interesting to note that this effect is more pronounced in the case of tantalite than it is for columbite, due to the higher rigidity of the former. Akimov and Chernyak [452] concluded that the effect of redistribution of the ions might cause the selective predominant dissolution of iron and manganese during the interaction with sulfuric acid and other acids. 

Figure 3. Schematic drawing of the crystal structure of f-MnOj. The manganese atoms are randomly distributed in the octahedral voids of the hexagonal dose packing of oxygen atoms (adapted from [47]).

The presence of the foreign cation stabilizes the crystal structure of a - Mn02 compounds. This manganese dioxide modification (more exactly it is not a real MnOz modification, since the structure contains a considerable proportion of foreign atoms) can be heated to relatively high temperatures (300 - 400 °C) without destruction of the lattice. Although Thackeray et al. reported the synthesis of cation-and water- free a - MnOz [49, 50J, which is reported to be stable up to 300 °C without destruction of the [2 x 2] tunnel structure, it is commonly believed that a small,... 

Figure 7. Crystal structures of (a) hollandite, (b) romanechite (psilomelane), and (c) todorokite. The structures arc shown as three-dimensional arrangements of the MnO() octahedra (the tunnel-tilling cations and water molecules, respectively, are not shown in these plots) and as projections along the short axis. Small, medium, and large circles represenl the manganese atoms, oxygen atoms, and the foreign cations or water molecules, respectively. Open circles, height z. = 0 fdled circles, height z = Vi.

The crystal structure of the mineral chalcophanite, ZnMn307-3H20 (see Fig. II), was one of the first layer structures of manganese oxides that has been determined. 

Figure 16. Crystal structure of a-MnOOH. The structure is shown as a three-dimensional arrangement of the Mn(0,0H)6 octahedra with the protons filling the [2 x 1] tunnels, and as a projection along the short crystallographic oaxis. Small circles, manganese atoms large circles, oxygen atoms open circles, height z - 0 filled circles, height z = A The shaded circles represent the hydrogen ions.

Berndt, A. F. Marsh, R. E. (1962) The crystal structure of cyclopentadienyl manganese tricarbonyl, C5H5Mn(CO)3, Acta Crystallogr. 16,118-123. 

However, the nature of these compounds could not be determined until in 1963 Danielsen et al. made a crystal structure analysis of the manganese compound (77). Later on these dichlorophosphates, in analogy to reaction (26), were prepared from dichlorophosphoric anhydride too ... 

A colorless mineral known as corundum (composed of aluminum oxide) is colorless. A red variety of corundum known as ruby, a precious stone, owes its color to impurities of chromium within the crystal structure of corundum. Blue and violet varieties of corundum are classified as sapphires, the blue being the result of iron and titanium impurities, and the violet of vanadium impurities within the corundum crystal structure. Another colorless mineral is beryl (composed of beryllium aluminum silicate) but blue aquamarine, green emerald, and pink morganite, are precious varieties of beryl including different impurities aquamarine includes iron, emerald chromium and vanadium, and morganite manganese. 

Manganese nitrosyl porphyrins [215] are considered good models for the iron-nitric oxide analogs, which are relatively unstable but very vital to many biological operations. A six-coordinate manganese nitrosyl porphyrin of the form (por)Mn(NO)(L), where por can be TTP (TTP = tetra(4-methylphenyl)porphine) and L = piperidine, methanol, 1-methyhmidazole, has been prepared [216] in moderate yields by the reductive nitrosylation of the (por)MnCl complex with NO in piperidine. The crystal structures of these compounds give indication of a linear Mn-NO bond [215]. 

Figure 19 Crystal structure of the wedged manganese complex, 3,3, 4,4 -Mn(TMEDA)-commo-Mn[2,3-(SiMe3)2-2,3-C2B4HJ2. Reproduced by permission of the American Chemical Society from Organometallics 1996, 15, 626.

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