D Orbital interactions

The method of generating MOs from LCAOs has been proved to be quite useful in establishing the relationship between the atoms and molecules from an electronic structure point of view. The ways in which s, p, and d orbitals interact with each other to form MOs of various symmetry kinds such as cr, tt, and 8 are depicted in Figure 3.2a through 3.2c, respectively. 

Fig. 12. MO diagram of Im-M(CH3)2J2 Mn(CO) 2 [e.g.. M = Ge (267)]. Note that metal-d-orbital interactions play a minor role. Reprinted with permission from K. Triplett and M. D. Curtis, J. Am. Chem. Soc. 97, 5747 (1975). Copyright 1975 American Chemical Society.

Quahtative information on the d bandwidth in perovskite can be acquired without carrying out these mathematical operations. This is accomplished simply by evaluating the p—d orbital interactions for some of the special points in the BZ. For now, the main focus is on the tt interactions between the metal t g and oxygen p orbitals. From Figure 3.5, it is expected that the Fermi level will lie in one of the t2g-block bands for n jiVOs oxides if B is an early transition metal with six or fewer d electrons. 

In the rock-salt stmcture, there are d-d orbital interactions between the 12 second-nearest neighbor metal atoms that must also be included. Figure 5.13 shows four of these dx -d cz interactions, two of which are if antibonding and two that are S bonding. The eight remaining d-d interactions are much weaker because of the poorer overlap... 

In the d o case of a singly-occupied metal d-orbital interacting with a doubly occupied ligand orbital (which in general will be a synnetry-adapted linear combination of atomic orbitals, see Table VI) the charge deformation can be written as (21) ... 

This table omits Jt-bonding effects, especially important for azo ligands. Pseudorotation of an amino substituent from an equatorial to an apical position costs a further [Pg.138]

The relative energies of molecular orbitals derived from d orbital interactions vary with different metals and ligands. For example, the order in [Ni(CN)4] matches that for d orbitals in Figure 10.16 (jc - > xz, yz > xy), but the Oiu, involving a p ... 

FIGURE 15.9 Relative Energies of Orbitals Formed from d-Orbital Interactions. In MjLg complexes, a pair of electrons from the ligands occupies the bonding orbital with high metal contribution. 

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