Octahedral coordination orbitals

The crystal field energy level diagram for octahedral coordination complexes. The energies of the d orbitals differ because of differing amounts of electron-electron repulsion. The... 

C20-0096. Use orbital sketches to explain why the d, and j2 y2 orbitals have different stabilities in octahedral coordination complexes. 

The ligand field of a quasi-octahedral coordination sphere acting on the (i-orbitals lifts the degeneracy of the excited spin quartet (and others) as sketched in tier (3). The nature of the resulting states and their energy depends on the strength... 

Figure 9.16 Color of Cu2+ ions in octahedral coordination (a) the electron distribution between the t2g and eg split d orbitals before and after absorption of radiation and (b) the absorption spectrum (schematic) of Cu2+ in CUSO4 5H20.

Titanium dioxide differs from silica mainly in two respects (1) the Ti + ions are octahedrally coordinated in all three modifications of TiOji (2) the Ti—0 bond is more pronouncedly ionic than the Si—O bond. Using Pauling s electronegativity values (297), one calculates a 63% ionic character for the Ti—0 single bond versus 50% for Si—O. In SiOj, there is certainly some double bond character involving 3d orbitals of the Si atom, causing lowered ionic character. Therefore, characteristic differences should be expected regarding the surface chemistry. 

For d orbitals placed in tetrahedral coordination, the t2 level contains the dyz, dxy, and dxz orbitals modified by the tetrahedral ligand field and the e level contains the d 2 and d 2-j2 orbitals. Figure 6 illustrates how the energy levels in tetrahedral coordination are inverted relative to those in octahedral coordination (Figure 6). 

At Xu = 0 Fe was found to be of intermediate stability in octahedral coordination. Unfortunately the valences of the Fe ions could not be clearly determined using the spin integration method of section 5 because the net spin on the Fe did not match a high-spin or low-spin configuration consistent with the average formal oxidation state (+4). This suggests that the d-orbital filling takes on an... 

Octahedrally coordinated transition ions with odd numbers of 3d electrons in the destabilized Cg orbitals (i.e., d, <7 , and low-spin d configurations) are subject... 

Fig. 1. Construction of molecular orbitals for octahedral coordination complexes of non w-bonding ligands utilizing metal 3

In solids where cation-cation interaction is significant, by can be related to R, where R is the cation-cation separation. In cases where cation-anion-cation interaction is important, by is related to the covalent mixing parameter, X, of the cation-anion orbitals. For octahedrally coordinated cations, as in rocksalt and perovskite structures, the relevant mixing parameters are and in the following molecular wave functions... 

Figure 7.5 A molecular orbital diagram for octahedrally coordinated transition metal ions...

In any cubic field, or in the case of octahedral coordination by eight anions, the 3d-state of a transitional-metal cation splits into six states of t2g symmetry with orbital wave functions of the form... 

The unique properties of lanthanide-based materials, e.g., lanthanide-silicates and lanthanide-doped silicas, can be related to the special properties of the 4f" orbitals. Among lanthanide oxides, only Ce, Pr and Tb form dioxides, which crystallize in one simple structure with M4+ ions showing octahedral coordination [17]. For instance, cerium dioxide exhibits an 8 4 catiomanion coordination [18]. Its characteristic feature is the ability to undergo oxidation-reduction cycles in a reversible way [19], It was shown that the presence of Ce and La additives in mesoporous silicas, e.g., MCM-41 [10,11] and MSU-X [12], improves their thermal and hydrothermal stability. 

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