Crystal field splitting is a measure of the “crystal field strength” of the ligand. The energy difference between the t 2 g and e g orbitals is called the octahedral crystal field splitting and is represented by the symbol 10 Dq (or sometimes by Δ). This increases the stability of the system. The single d electron in a Ti 3+ complex will avoid the areas of higher energy and higher electronic repulsion at the corners of the octahedron and enter one of the t 2 g orbitals.
One of the successes of crystal field theory has been in explaining the spectra of complexes.) The changes in energy levels can be pictured as follows: (These names are derived from spectroscopic terms.
The three orbitals of lower energy are called t 2 g orbitals (pronounced “t-two-g”) and the two of higher energy are called e g orbitals (pronounced “e-g”). The other three orbitals are further from the negative charge of the donor atoms and are at a lower energy than they would be in a symmetrical field. These orbitals are therefore raised in energy relative to their positions in a symmetrical field. Comparison with the arrangement of the d orbitals in Figure 28.8 shows that the two lobes of the d z 2 orbital and the four lobes of the d x 2- y 2 orbital point directly toward the corners of the octahedron, where the negative charge of the approaching ligands is concentrated.
However, the ligands approach along the x, y, z coordinates as shown in Figure 28.9, producing an octahedral field.
0 kommentar(er)
