MO-diagram

Using these approximate energies we ean draw the following MO diagram ... 

By applying these rules and recognizing the elements of symmetry present in the molecule, it is possible to construct MO diagrams for more complex molecules. In the succeeding paragraphs, the MO diagrams of methane and ethylene are constructed on the basis of these kinds of considerations. 

The kind of qualitative considCTations that have been used to construct the ethylene MO diagram do not give an indication of how much each AO contributes to the individual... 

Fig. 1.28. MO diagram showing mutual perturbation of MOs of butadiene and allyl cation.

Construct a qualitative MO diagram showing how die rt-molecular orbitals in the following molecules are modified by die addition of die substituent ... 

Use PMO theory to describe the effect of the substituents on the ionization potential. Use an MO diagram to explain the interaction of the substituents with the n bonds. Explicitly take into account the fact that the two orbitals interact and therefore cannot be treated as separate entities (see Problem 10). 

Provide a rationalization of this structural effect in terms of MO theory. Construct a qualitative MO diagram for each conformation, and point out the significant differences that can account for the preference for the eclipsed conformatiptL... 

The hydrocarbon phenalene is the precursor of both a highly stabibzed anion and a highly stabilized cation. The Huckel MO diagram is shown in Fig. 9.7. The single orbital at the nonbonding level is the LUMO in the cation and the HOMO in the anion. The stabilization energy calculated for both would be the same and is 0.41/3 by the HMO comparison. ... 

Fig. 10.2. MO diagram for anisole by applicatbn of perturbation for a methoxy substituent.

The excited carbonyl groups have radical character at both carbon and oxygen, and the oxygen is rather similar in its reactivity to alkoxyl radicals. The MO diagrams for the n-n and 7t-7t states can be readily depicted ... 

Figure 24.10 Spin equilibrium in [Mn(ij -C5H4-Me)2] the orbitals shown here are the mainly metal-based orbitals in the centre of the MO diagram for metallocenes (see Fig. B, p. 939).

I osmyl complexes (a) 3-cenire rr bond formed hy overlap of ligand p, and nilar tv>nd is produced hy p, and d,. ovcrlapi, and Ihi MO diagram Isee lexij,... 

Figure 4. The calculated spectrum of the complex after a Lorentzian band convolution. Region I is dominated by bridging-sulfur-to-iron CT transitions, while region II is mostly due to organic-sulfur-to-iron electron transitions. Regions I and II are explained in a MO diagram. The vertical lines correspond to the experimental bands observed in the absorption spectrum of the [Fe2 (J. - S2) P o - CqH4S) ) ] complex, from Reference 1.

Fig. 15. Schematic MO diagram and proposed electronic assignments for the Fe-Fe interaction in a valence-delocalized S = 9/2 [Fe2S2] unit. Modified with permission from Ref. (207).

The MO diagram shown in Figure 10-28 can be applied to any of the possible diatomic molecules or ions formed from the first-row elements, hydrogen and helium. Count the electrons of He2" , place the electrons in the MO diagram, and calculate the bond order. If the bond order is greater than zero, the species can form, under the right conditions. 

One He atom has two electrons, so a He2 cation has three electrons. Following the aufbau process, two electrons fill the lower-energy cr 1 orbital, so the third must be placed in the antibonding crj orbital in either spin orientation. A shorthand form of the MO diagram appears at right. The bond order 1... 

Recall from Chapter 8 that ionization energy refers to the removal of an electron from an atom, or, in this case, from a molecule. We must count the valence electrons, choose the correct MO diagram, follow the aufbau process in placing the electrons, and then use the configurations to explain the ionization energy data. 

Applying the general diatomic MO diagrams of Figure 10-35 gives the following... 

Figs. 11 and 12 show typical mo diagrams for square planar and octahedral complexes. Inspection reveals that the metal orbital (z is the axial direction) in a square planar complex is involved in the n bonding system and available for a bonding in the transition state. This is a feature shared by nucleophilic substitution at square planar complexes with the spectacularly associative nucleophilic aromatic substitutions. The octahedral complexes discussed in this chapter... 

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