Manganese atoms

Manganese, atomic no. 25, belongs to the first transition series and is the principal member of Group 7 (VIIA). It has nine isotopes (1,2) (Table 1). Table 1. Isotopes of Manganese... 

The nitrogen atom in ri -pyrrolylmanganesetricarbonyl forms a donor-acceptor bond with transition metals. Complexes in which the pyrrolyl ring behaves as a tt ligand for the manganese atom and n-donor for the other metal were synthesized 12 (M = Mn, Re) [78JOM(157)431]. The binuclear heterobimetallic complexes... 

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 manganese atoms are distributed in a more or less ordered manner at the slightly distorted octahedral voids in the hexagonally close-packed oxygen atoms (as described above). 

A fraction y of the Mn4+ ions are replaced by Mn3+. This fraction determines the average valence of the manganese atoms. For each Mn,+ there is a further OH ion in the lattice, replacing an O2 anion in the coordination sphere of the Mn3+ cation. A schematic drawing of the Rue-tschi model is shown in Fig. 4. 

Figure 6. Projection of the manganese atoms in the ramsdellite lattice onto the be-plane. The oxygen atoms are not shown. The twinning planes [02l (above) and [061] (below) are marked with arrows. The twins at these planes are generated by rotating the shaded ramsdellite cells by either 60° or 120° around the a-axis. (Adapted from Ref. [47].)...

In Fig. 6 the arrangement of the manganese atoms is shown in a projection along the a-axis. The unit cells are marked by the shaded regions. It can easily be seen, that no lattice distortion is necessary to form... 

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.

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.

FIGURE 16.44 The structure of a molecular magnet. The nano-size molecular torus contains 84 manganese atoms and is approximately 4 nm in diameter. The manganese atoms are bonded to groups of carbon atoms in the form of acetate ions, water molecules, and chlorine atoms. In this molecule the manganese atoms act as terromagnets. 

It is found that chromium atoms, manganese atoms, and tin atoms exist in metals in two forms, a small, high-valent form and a larger, low-valent form. The two kinds of manganese atoms coexist in a-manganese and in /3-manganese. 

It was pointed out by Bradley and by Hume-Rothery22 that the nature of the a-manganese structure suggests that there are manganese atoms present of two different sizes, and a study... 

Manganese atoms were cocondensed with Oj, N2O, or O3, to afford MnO, Mn02, MnOs, and Mn04 (197). The actual reactions involved were... 

The Mn-S distances vary from 2.32 (1) to 2.35 (1) A, whereas in Mn(Et2rftc)3 the manganese atom is surrounded by three opposing pairs of sulfur atoms at distances of 2.38 (1), 2.43 (1) and 2.55 (1) A (47). Electrochemical studies (43) in acetone and dichloromethane showed one-electron transfer series ... 

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