Crystal field splitting consequences

In the transition metal ions of periods 5 and 6 (which have 4d and 5d valence electrons), the d orbitals are larger than in the period 4 ions (which have only 3d electrons). Thus, ions from periods 5 and 6 interact more strongly with ligands, resulting in a larger crystal-field splitting. Consequently, metal ions in periods 5 and 6 are invariably low spin in an octahedral crystal field. 

The loss of degeneracy of atomic or molecular levels in a molecular entity with a given symmetry by the attachment or removal of ligands to produce reduced symmetries. Ligand field theory treats metal ligand complexation as a consequence of molecular orbital formation, whereas crystal field splitting considers ligands as point... 

The f electrons within the 4fn configuration of the lanthanides have only weak interactions with the crystal field because they are shielded by outer 5s and 5p electrons. Consequently the spectra are dominated by transitions between the atomic states of the lanthanide ion. The left side of Figure 1 shows the ionic energy levels of Eu3+ in the gas phase. When the ion enters a crystal lattice, there will be additional crystal field interactions. The interactions cause small crystal field splittings on the order of 200 cm-1 that are superimposed on the atomic transitions and are easily observable. 

The most remarkable aspect of Eq. (14-10) is that the dependence upon bond length and therefore, the dependence upon which alkali halide is being considered—has cancelled out. Another consequence is that the ion. softening does not depend upon pre.ssurc. This explains why theories of the crystal-field splitting and its pressure dependence that arc based upon hard ions have been successful the 0.51 factor can be absorbed in an undetermined scale parameter, depending upon the shape of the orbitals being split, since the factor 0.51 does not change with distortion. 

PdCl4] and [PtCl4] (also d ) are square planar and diamagnetic. This dilference is a consequence of the larger crystal field splitting observed for second and third row metal ions compared with their first row congener Pd(II) and Pt(II) complexes are invariably square planar (but see Box 21.6). 

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