Square planar complex energy level diagram

Suggest the form that the orbital energy-level diagram would take for a square planar complex with the ligands in the xy plane, and discuss how the building-up principle applies. Hint The d -orbital has more electron density in the xy plane than the dzx- or d -orbitals but less than the dXJ,-orbital. 

In a nickel-containing enzyme various groups of atoms in the enzyme form a complex with the metal, which was found to be in the +2 oxidation state and to have no unpaired electrons. What is the most probable geometry of the Ni2+ complex (a) octahedral (b) tetrahedral (c) square planar (see Exercise 16.96) Justify your answer by drawing the orbital energy-level diagram of the ion. 

FIGURE 17.20 A molecular orbital energy level diagram for a square planar complex. 

Fio. 26. Energy level diagram of 3cP configuration (Cu" " ) in square planar complex or tetragonal crystal field (CF). Effect of bonding of the 3d-electrons with ligands is shown. 

Suggest the form the orbital energy-level diagram would take for a square planar complex and discuss how the building-up principle applies. Hint ... 

Fig. 1 Simple ligand field-splitting diagram for metal d orbitals in a square planar complex. By convention, the z axis is perpendicular to the plane of the complex and the M - L bonds lie along the x and y axes. Note that the exact ordering of the lower energy levels depends on the ligand set (e.g., relative importance of a- and 7r-effects) but the dX2-y2 is always unequivocally the highest...

A coordinate system for a square-planar complex ML4 (Z>4h symmetry) is displayed in Fig. 8.9.1. The linear combinations of ligand orbitals, matched in symmetry with the metal orbitals, and the molecular orbitals they form, are summarized in Table 8.9.1. A schematic energy level diagram for this type of complexes is given in Fig. 8.9.2. 

Schematic energy level diagram for a square-planar complex ML4. Note the block of levels labelled n is present only for ligands with low-lying it orbitals such as CO, CN, and PR3.

With the energy level scheme shown in Fig. 8.9.2, we can easily derive two types of energy level diagrams those for halides, as shown in Fig. 8.9.3, and those for cyanides, as shown in Fig. 8.9.4. We will make use of these results to interpret some spectral data for square-planar ML4 complexes. 

To understand why 16-electron square planar complexes might be especially stable, it is useful to examine the molecular orbitals of such a complex. An example of a molecular orbital energy level diagram for a square planar molecule of formula ML4 (L= ligand that can function as both s donor and n acceptor) is shown in Figure 3-7. 

FIGURE 22.24 Energy-level diagram for a square-planar complex. Because there are more than two energy levels, we cannot define crystal field splitting as we can for octahedral and tetrahedral complexes. 

Figure 3.9. Simplified mDlecular orbital diagram for the energy levels in square planar complexes.

In Figure 52 is shown a schematic energy level diagram for square-planar complexes. The diagram shows the energy gap AE between the highest filled and the lowest unfilled M.O.s. 

Fig. 52. Schematic energy level diagrams for square-planar complexes. represents the energy gap between the highest occupied orbital and the lowest unoccupied orbital. I represents the case when there is only a-bonding and II shows how A is increased when there is a -bonding interaction in the

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