Orbital splitting and electron spin

Strong ligand field large A low spin Weak ligand field small A high spin 

TABLE 10.5 Spin States and Ligand Field Strength 

Complex with Weak-Field Ligands (High Spin) 

Complex with Strong-Field Ligands (Low Spin) 

For example, a metal center could have five unpaired electrons, three in t2g and two in 6g orbitals, as a high-spin case or it could have only one unpaired electron, with all five electrons in the t2g levels, as a low-spin case. The possibilities for all cases, through d, are given in Table 10.5. 

FIGURE 10-5 Molecular Orbitals for an Octahedral Transition Metal Complex. As in Chapter 5, the symmetry labels of the atomic orhitals are capitalized and the labels of the molecular orbitals are in lowercase. (Adapted from R A. Cotton, 

Chemical Applications of Group Theory, 3rd ed., Wiley-Interscience, New York, 1990, p. 232, omitting ir orbitals. 1990, John Wiley Sons, Inc. Reprinted by permission of John Wiley Sons, Inc.) 

SO there is no difference in the net spin of the electrons for strong- and weak-field cases. On the other hand, the through ions exhibit high-spin and low-spin states, as shown in Table 10-5. Strong ligand fields lead to low-spin complexes, and weak ligand fields lead to high-spin complexes. 

Strong ligand field = large = low spin Weak ligand field = small A = high spin 

As explained in Section 2-2-3, the energy of pairing two electrons depends on the Coulombic energy of repulsion between two electrons in the same region of space, II., and the purely quantum mechanical exchange energy,. The relationship between the 

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