Eg orbitals

Weak M-L interactions lead to small stabilization of eg orbitals and small destabilization of e ... 

Not even the slightest Jahn-Teller distortion and therefore no deviation from the ideal octahedral symmetry are to be expected when the t2g and eg orbitals are occupied evenly. This applies to the following electronic configurations ... 

Multipole analysis with high-resolution X-ray data for [Ni(thmbtacn)]2+ was carried out to determine the electron configuration in the C3 symmetry-adapted orbitals of the Ni ion, confirming a higher occupancy of the crystal field-stabilized t2g orbitals relative to the destabilized eg orbitals. This is interpreted in terms of a predominantly ionic metal-ligand interaction.1424... 

From a consideration of the combination of ligand and metal orbitals, it should be apparent that the overlap is much more effective in an octahedral complex (in which orbitals are directed at ligands) than in a tetrahedral complex (where orbitals are directed between ligands). The result is that the energy difference between the e and t2 orbitals in a tetrahedral complex is much smaller than that between the t2g and eg orbitals in an octahedral complex. As we saw when considering the two types of complexes by means of ligand field theory, At is only about half as large as A0 in most cases. 

A high spin complex is the Crystal Field designation when all t g and eg orbitals are singly occupied before pairing begins. A low spin complex, on the other hand, is the Crystal Field designation, where electrons paired in t2g orbitals before eg orbitals are occupied. The low spin configuration can exist only for octahedral... 

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