Square pyramidal crystal field, splitting

Using the square pyramidal crystal field splitting diagram given in Problem 5.37, verify the change in the CFSE given in Table 5.4 for a metal ion with a low-spin... 

The crystal field splitting diagram for a square pyramidal crystal field is given... 

Fig. l.i. Crystal field splitting diagrams for (a) octahedral MLh, (b) tetrahedral ML4, (c) square planar ML4, (d) square pyramidal MLS and (e) trigonal bipyramidal ML5. 

If we examine the two five-coordinate shapes from a crystal field perspective, the d orbitals split in a different way to that found for octahedral, tetrahedral and square planar shapes since the d orbitals find the ligands in clearly different locations in space. The crystal field splitting pattern for the two is shown in Figure 4.14. From this pattern, crystal field stabilization energies can be calculated, and favour the square pyramidal geometry in all cases (apart from the trivial situations d° and d10) except for high spin d5. This prediction differs from the outcome from the electron pair repulsion model. 

Crystal field splitting pattern for trigonal bipyramidal (left) and square pyramidal (right) ML5 complexes. 

A given square pyramidal RUL5 complex containing Ru (d ) has a magnetic moment of 2.90 BM. Calculate the CFSE of this complex. Start by placing the six electrons in the above crystal field splitting diagram. 

The hexacyanoferrate(II) ion, [Fe(CN)g], is a strong-field/low-spin complex. Calculate the change in crystal field splitting energy (ACFSE) in kJ/mol for this complex ion when one of the cyanide ligands is dissociated to form a square pyramidal intermediate. Hint Consult Tables 4.2 and 5.4 for necessary information.)... 

FIGURE 1.5 Crystal field splitting patterns for the common four- and five-coordinate geometries tetrahedral, square pyramidal, and square planar. For the square pyramidal and square planar arrangements, the z axis is conventionally taken to be perpendicular to the L4 plane. Octahedral geometry is expected for d while square planar and square pyramidal are preferred in d the A HOMO-LUMO splittings shown apply to those d " configurations. 

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