Sigma -donor ligand

FIGURE 10-20 Energies of d Orbitals in Octahedral Complexes Sigma-Donor Ligands. A, =... 

Point Group and Site Symmetries for Various Oxygen Coordination Environments and the Irreducible Representations of the most Symmetric Sigma Donor Ligand Symmetry Adapted Linear Combination, and the Oxygen 2p Orbitals... 

As a simple example of non-d coordination, let us consider the hexaammine-zinc(II) cation [Zn(NH3)6]2+, whose optimized structure is shown in Fig. 4.51. Each ammine ligand serves as a formal two-electron sigma donor, and the total electron count atZn therefore corresponds to a 22e system, again violating the 18-electron rule. Each ammine ligand is bound to the Zn2+ cation by about 60.7 kcal mol-1, which is in part attributable to classical electrostatic interactions of ion-dipole type. 

The bonding between the transition metal and the group 13 element has been studied extensively by computational methods. Because RM compounds have a valence electroitic structure consisting of a filled orbital of a symmetry and two unfilled orbitals of n symmetry, they are analogous to carbonyl ligands in that they can act as sigma donors and pi acceptors see tv-Acid Ligand). Such an electronic structure... 

FIGURE 10-24 Energies of 4 Orbitals in Octahedral Complexes Sigma-Donor and Pi-Donor Ligands. Ao = - Ae.y. Metal s and p... 

Assign the symmetry labels of the d orbitals (labels of the irreducible representations). Repeat the calculations in Part a for a ligand that can act both as a sigma donor and a pi acceptor. 

FIGURE 10.5 Sigma-Donor Interactions with Metal s, p, and d Orbitals. As in Chapter 5, the symmetry labels of the atomic orbitals are capitalized, and the labels of the molecular orbitals are in lowercase. The six filled ligand donor orbitals contribute 12 electrons to the lowest six molecular orbitals in this diagram. The metal valence electrons occupy the and,... 

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