L- M Charge Donation

Mixing of metal and ligand orbitals accounts for covalency. Covalency is often incorrectly referred to as hybridization. The term hybridization should be reserved for mixing of orbitals on the same atom with different if quantum numbers. In LFT, a bonding and an antibonding MO with the same symmetry indices are formed, as already mentioned. This linear combination may be written as  

This form of MO assumes that the atomic orbitals Xl and Xm are orthonormalized, but we will not discuss this here. In Equation 6.18, trigonometric coefficients (cos 0 and sin 0) are used to conserve orthonormalization. CFT corresponds to the case 0 = 0, where only the 3d (4d, 5d) orbitals are treated. Notice that if both (), and ( 2 are fully occupied, there is no charge or spin transfer contribution because cos 0-l-sin 0=l. Equation 6.18 has been verified in several calculations without restrictions on form. 0 may be determined using hyperfine structure, spectroscopy, or calculations, provided, of conrse, that the orbital pair in Equation 6.18 is not fully occupied. 

FIGURE 6.8 The 4 , = (bonding) and t)2= b,g (antibonding) pair of MOs with the symmetry — y. The latter MO is unoccupied in the Ctf 3d -singlet ground state. 

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