Metal/oxygen displacement

Nitrogen Displaces the Metal Phosphorus Displaces the Metal Oxygen Displaces the Metal Sulfur Displaces the Metal Fluorine Displaces the Metal Chlorine Displaces the Metal Bromine Displaces the Metal Iodine Displaces the Metal... 

The ground-state distortion (Table I) from the normal octahedral geometry, i.e., the displacement of the central metal atom by up to 0.34 A toward the oxo from the plane formed by the four cyano carbon atoms, is in further agreement with this reasoning, indicative of more reactive complex with an increased metal-oxygen bond length. 

In some cases, the CFSE attained by a transition metal ion in a regular octahedral site may be enhanced if the coordination polyhedron is distorted. This effect is potentially very important in most silicate minerals since their crystal structures typically contain six-coordinated sites that are distorted from octahedral symmetry. Such distortions are partly responsible for the ranges of metal-oxygen distances alluded to earlier, eq. (6.6). Note, however, that the displacement of a cation from the centre of a regular octahedron, such as the comparatively undistorted orthopyroxene Ml coordination polyhedron (fig. 5.16), also causes inequalities of metal-oxygen distances. 

The polyhedral (MO ) building blocks of virtually all polyoxoanions are linked in such a way as to result in each polyhedron having either one or two (mutually cis) unshared vertices. The metal atoms are displaced from the centers of their coordination polyhedra toward these unshared vertices. These displacements correspond to the formation of short metal oxygen terminal bonds resulting from oxygen Pjt donation into the metal s vacant d-orbitals. Such terminal oxygens, which are very weakly basic, form part of the external surfaces of the polyoxoanions and effectively prevent fruther polymerization. Very rarely (about three examples... 

Iron is an active metal, which displaces hydrogen easily from dilute acids. It burns in oxygen to produce ferrous-ferric oxide, FcgO. This oxide is also made by interaction with superheated steam. One metnod of preventing rusting involves the production of an adherent surface layer of this oxide on iron. 

Selective epoxidation of olefins by vanadium(V) alkyl peroxo complexes has also been reported (76). These complexes are very effective stereo-selective reagents for the transformation of olefins into epoxides. The mechanism consists of binding of the olefin to the metal to displace one of the peroxo-oxygen atoms, nucleophilic attack of the bound oxygen atom on the coordinated electron-deficient olefin, dissociation of the epoxide, and reaction of the remaining vanadium intermediate with... 

The reason for the numerous modifications originates in the structure, which is a three-dimensional array of comer-sharing metal-oxygen octahedra (Fig. 4.3). The idealized structure (cubic symmetry ReOs-type) is drawn in Fig. 4.4, showing the octahedra as squares in projection. The real stmcture is distorted. This means that the relatively small tungsten atoms tend to be displaced from the octahedral center and diese displacements are temperature-dependent. Moreover, the symmetry can be influenced by small amounts of impurities. 

The relative Gibbs free energies of the reactions of metals with oxygen tell whether or not a particular metal will displace the aluminum in alumina. The reaction of aluminum with oxygen is... 

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