Walsh-type diagram

Figure 14-9 The Walsh-type diagram for the HAB system (a) linear Cqov (b) bent Cs. (After Gimarc [6].) Reprinted with permission from Accounts Chem. Res. 7, 384 (1974). Copyright by the American Chemical Society.

Figure 14-13 Walsh-type diagram for i sd- Sh A2H6 (a) Z>3d (staggered) (b) D h (eclipsed). Note that the e-type MOs for the two forms do not turn into each other by rotating about the C-C bond. This is really a two-sided correlation diagram, the high symmetry of each form determining the MOs. Then QMOT rules are used to decide how similar MOs on the two sides should relate in energy. (See Lowe [9].)...

Figure 1. Walsh type orbital correlation diagram (EH MO calculations [6]) for transforming linear H3P-Pt-PH3 (D3h) to a bent (C2V) geometry. Only the valence MOs and the relevant metal contributions to the MO wave functions are shown. 

Fig. 3. Walsh correlation diagrams, a State energy levels for methylene (Jordan and Longuet-Higgins, 1962). 6 MO levels after Walsh (1963). c MO levels after Atkins and Symons (1967) and Hayes (1966) above the break, ci-type orbitals have been included their effect on the energy of some MO s is indicated by the small arrows.

Figure 14-8 The Walsh-type correlation diagram for HAH (a) linear Dooh ( ) C2v The cross-hatched parts of MOs have opposite sign from open parts.

Walsh-type correlation diagrams have been consttucted and discussed for many systems, among them AH3, HAB, HAAH, BAAB, H2AAH2, B2AAB2, H3AAH3. It is not appropriate that these all be described here. We will briefly discuss two more cases that bring in some additional features. 

Figure 14-12 Walsh-type correlation diagram for — Z>2h shapes of H3 AAH3. (After Gimarc...

The Walsh diagram shown m Fig. 6.16 is accurate only for molecules in which there is a large separation between the ns and np energy levels of the central atom. If the ns-np separation is small (as in SrF2 and BaFz). the lb2 level (of Fig. 6.16) does not rise as rapidly as 2a, fells, and the molecule may be stabilized on bending.26 Note that in MFa molecules of this type, the 3o, and I bt levels are unoccupied. 

According to the correlation diagram of Walsh (4) for HAB type molecules, NaOH should be Therefore, we assume the ground state to be... 

A special case is met when the substiment is the cyclopropyl group, because of the presence of high-lying almost r-type cr-orbitals. These orbitals, Wa and Ws, shown schematically in diagram 36, have been introduced by Walsh to explain the properties of molecules containing the cyclopropane moiety. 

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