Octahedral complexes energy-level diagram

In a nickel-containing enzyme various groups of atoms in the enzyme form a complex with the metal, which was found to be in the +2 oxidation state and to have no unpaired electrons. What is the most probable geometry of the Ni2+ complex (a) octahedral (b) tetrahedral (c) square planar (see Exercise 16.96) Justify your answer by drawing the orbital energy-level diagram of the ion. 

The crystal field energy level diagram for octahedral coordination complexes. The energies of the d orbitals differ because of differing amounts of electron-electron repulsion. The... 

FIGURE 17.16 Ihe molecular orbital energy level diagram for an octahedral complex. 

Although we will not write the complete wave functions as we did for the case of an octahedral complex, the molecular orbitals give rise to the energy level diagram shown in Figure 17.20. 

Figure 2.6 Simplified MO energy-level diagram for the formation of a o-bonded octahedral ML6 complex in which there are no tt-bonding interactions between metal and ligand.

Figure 1.23 General energy level diagram for an octahedral complex (A) and energy levels of pyrite (B). Part (B) from Burns and Vaughan (1970). Reprinted with permission of The Mineralogical Society of America.

With reference to the octahedral energy level diagrams for oxy, car-boxy and deoxy hemoglobin derived from extended Huckel calculations and our earlier work on the natural heme complexes, the results of this study can be discussed. 

Fig. 12. Schematic energy level diagram illustrating the Jahn-Teller stabilization energy accompanying a tetragonal elongation of an octahedral Cu(II) complex.

By inspection of the energy level diagrams it is possible to see directly what sort of spectrum the ion should have in the given environment. For example, it can be seen from Figure 9.3 that a d2 ion in an octahedral complex, say [V(H20)J3+, should have three spin-allowed transitions, from the 37, ground state to the upper states 37, 3T, and 3A2. Experimentally, two absorption bands have been found at —17,000 and —24,000 cm-1, and these may be assigned to the T — 37 and 3T - 3T transitions if A0 is taken as —21,500... 

All three complexes are octahedral, so the energy-level diagrams will show three lower-energy and two higher-energy d orbitals. For d1 -d3 and dH-d10 complexes, the electrons occupy the orbitals in accord with Hund s rule so as to give the maximum number of unpaired electrons. For d4-d7 complexes, the orbital occupancy and number of unpaired electrons depend on the position of the ligand in the spectrochemical series. 

Figure 11.4 Energy level diagram for an octahedral transition metal complex showing the various kinds of electronic transition. MC = metal-centred, LC = ligand-centred, MLCT = metal-to-ligand charge transfer, LMCT = ligand-to metal-charge transfer.

FIGURE 5.26 Energy-level diagram for Co(III) complexes in an octahedral and a trigonal field. 

FIGURE 5.28 Energy-level diagram for Cr(III) complexes in octahedral and trigonal fields. 

After determining what levels are present for an octahedral complex with a given electronic configuration, we are now ready to discuss the energy level diagrams for these spectroscopic terms. 

Energy level diagram for a octahedral complex, ignoring second-order crystal field interaction. 

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