Nonbonding orbitals octahedral complexes

The molecular orbital model can also be applied to complexes of the d-block elements. In octahedral complexes the d-orbitals of the metal are not degenerate, as they are in the free metal, because of the interaction between the ligand and metal orbitals. The five d-orbitals are split into three t2g (nonbonding) and two e (antibonding) MOs that is ... 

A representative molecular orbital diagram for an octahedral d-block metal complex ML6 is shown in Figure 1.8. The MOs are classified as bonding (oL and ttL), nonbonding (jtM) and antibonding (o, nl and ). The ground-state electronic configuration of an octahedral complex... 

Figure 6.17 MO energy level diagrams which include nonbonding ligand n orbitals for an octahedral complex, [MLg] (a) n donor ligands (b) n acceptor ligands. The terms LMCT and MLCT are discussed in Section 7.2.2...

Therefore, there cannot be any interaction between the three xy, xz, and yz orbitals and the ct orbitals on the ligands. In an octahedral complex, these three d orbitals therefore form a degenerate nonbonding set, located only on the metal (2-18 to 2-20). 

The analysis presented above allows us to establish the main features of the orbital structure of octahedral complexes. It also shows that certain molecular orbitals are degenerate. This is the case, for example, for the three bonding MO constructed from the metalp orbitals (2-9, 2-11, and 2-13), or for the three nonbonding orbitals (2-18 to 2-20). However, other degeneracies exist which caimot readily be shown by the analysis above. To obtain a more complete description of the orbital structure, it is necessary to exploit all the symmetry properties of the octahedron and not simply this or that symmetry element as we have done so far. 

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