In octahedral environment

Recall the splitting of the d orbitals in octahedral environments. The energies of the t2g and g subsets are shown in Fig. 8-4 with respect to their mean energy. We have used the conventional barycentre formalism. In effect, we express the energy of an electron in the t2g or orbitals with respect to the total energy possessed by a set of five electrons equally distributed amongst the five d functions. Alternatively, we say that our reference energy is that of 2l d electron within the equivalent spherical mean field. 

Two simple Cd arsenates have been described, namely Cd2As2C)7, with a ditetrahedral anion 287, and CdAs206, with both Cd and As in octahedral environment.288... 

Fig. 2. Energy level splitting of Cr3+ in octahedral environment and after tetragonal distortion.

Neutral trans- and cis- complexes were obtained for Cu11 and Mn11 ions (Fig. 6b, c) respectively [49]. The metallic ion in octahedral environment is coordinated to four oxygen atoms of two hfac ions and two nitrogen atoms of two TTF CH=CH—py... 

Fig. 3 Top side view of a layers of Zn(03PCH3) H20 Zn atoms are in octahedral environment and share four corners with neighboring octahedrons...

Mixed donor ligands. Tris(acetylhydrazine)iron(iii) trichloride has been pre-pared. ° The effect of pressure on ferric hydroxamates is to cause reduction to iron(ii), the amount of reduction being correlated with the position of the metal-> ligand charge-transfer band. Fe " complexes of A-hydroxyurea have been isolated. 8-Amino-7-hydroxy-4-methylcoumarin (58) forms the complex [FegLjCl ], in which the Fe " ions are in octahedral environments. A magnetic and Mossbauer study of [FeX(ox)2] and [FeX2(ox)] (X = Cl or... 

Although Ti " " is almost always octahedrally coordinated, it is often found displaced from the centre of its coordination sphere, as for example in BaTiOs (23759, Fig. 10.4), where, even though the distortion is driven by the lattice strains discussed in Chapter 12, it is stabilized by a favourable electronic state. Even when Ti " " possesses a crystallographic centre of symmetry as in SrTi03 (201256), it is probable that it is dynamically distorted (Abramov et al. 1995). By contrast, Sn, which is similar in size to Ti, is found in octahedral environments that are rarely distorted. Tetrahedral Ti is known in Ba2Ti04 (2625) but in very few other compounds. 

The potassium ions are located between the flat aluminosilicate sheets (Fig. 7.4). Crystals of micas cleave easily parallel to the sheets, and the thin transparent flakes can be used for electrical insulation (e.g., in capacitors) or as furnace windows. Phlogopite, KMg3(OH)2[Si3A10io], has a similar structure but with Mg2+ in octahedral environments instead of Al3+. 

In Figure 9.5 are shown energy ievel diagrams for all of the dn configurations in octahedral environments. These diagrams are plotted in a manner requiring some comment. Instead of using absolute units for the ordinate and abscissa... 

In a complex that possesses a center of symmetry, all states arising from a dn configuration have the g character inherent in the d orbitals. Since the dipole moment vectors belong to odd representations, all of the integrals such as / y/gXi//g dr are identically zero because the direct product of two g functions can never span any u representations. On this basis alone, we would predict that transitions between the various states arising from dn configurations in octahedral environments would have zero absorption intensity. In fact, these transitions do take place but the absorption bands are only —lO"3 times the intensity expected for symmetry allowed electronic transitions. Thus the prediction we have made is substantially correct, but at the same time there is obviously some intensity giving mechanism that has been overlooked. 

Both nickel(III) and nickel(IV) complexes are usually found in octahedral environments. Less common geometries are the square planar and the trigonal bipyramidal ones. 

Natural macrocycles displaying antibiotic propenies are also very efficient in the recognition of alkali metal ions. For instance, valinomycin (5 in Fig, 3) gives a strong and selective complex in which a K+ ion is included in the macrocyclic cavity in octahedral environment of six carbonyl oxygens (Fig. 4). 

Almost aU these complexes had a hexacoordinated tin atom in octahedral environment. It is remarkable that only five intermolecular coordination compounds Me3SnX B (Cl, Br, I B = Py, PhNH2 ) containing pentacoordinated tin atom... 

Applying Eq. 31 to determine the splitting energies with pa representing the lanthanide cation offers an alternative computational strategy to address this problem. This type of application of Eq. 31 can be seen as the first-principles based realization of such past attempts to refine ligand-field theory which take into account non-electrostatic effects61. In octahedral environment, such as the one occur-... 

Fig. 19. The differences between the t2u and U2u levels (in cm-1) in octahedral environment for the whole lanthanide series. Squares are used for experimental data. Full and empty circles correspond to KSCED results obtained with relaxed (polarized) or not-relaxed (not polarized) electron density of the ligands, respectively. Lines are used to guide the eye. Theoretical data taken from [Zbiri ef at, Chem. Phys. Lett., 397, (2004) 441]. Experimental data taken from [Richardson et at, J. Chem. Phys, 83 (1985) 3813].

Physico-chemical characterisation was performed to have some indications about the changes undergone by the catalysts because of deactivation. All the fresh copper zeolite samples presented the typical XRD pattern of the parent zeolites, without any signal due to bulk copper oxide. DRS spectra showed the characteristic absorption (650-1000 nm) due to the d-d transitions expected for Cu in octahedral environment of 0-containing ligands [20]. 

About 15 % of Fe(III) has a cubic coordination environment. This type of coordination can be assigned to isolated Fe(III) ions in octahedral environment of oxygen, which is characteristic of cubic In203 modification. Moreover, y-Fe203 can possess cubic structure... 

We now consider the distribution of electrons on metal ions in octahedral environments. If only one d electron is present it must clearly occupy one of the more stable set of f2 orbitals. If more than one d electron is present, however, complications may arise for in such cases there are two competing tendencies at work. 

Figure 2, The crystal and molecular structure of (Me -Si)fiH] SnCr(CO)s (15)—Sn-Cr, 2,562 A Sn-C, 2,19 A < C-Sn-C, 95 < C-Sn-Cr (mean), 13V CoSnCr-(CO)g essentially coplanar with Cr in octahedral environment...

---