Molecular orbital schemes

Figure 2.38 The effect of varying the relative energies of the metal and ligand orbitals upon the final molecular orbital scheme for a dimeric rhodium carboxylate. (Reprinted from Coord. Chem. Rev., 50, 109, 1983, with kind permission from Elsevier Science S.A., P.O. Box 564,...

Figure 4.17 A qualitative molecular orbital scheme for a cr-bonded complex ion [AuL2]+. (Reprinted with permission from Inorg. Chem., 1982, 21, 2946. Copyright (1982) American...

FIGURE 3.35 The molecular orbital schemes typical of those calculated for a diatomic oxide molecule, EO (where E = C for CO and E = N for NO). Note that the D-orbitals are formed from mixtures of s- and p/-orbitals on both atoms accordingly, we label them simply Id,... 

Two possible molecular orbital schemes, (3) and (4), are shown in the accompanying diagram. Orbital scheme (3) involves a cyclic array of six... 

The considerable number of molecular orbital calculations which have recently been made for sandwich compounds are however considered in some detail in Section 6. This has been done in order to make clear the relationship between the ligand field and molecular orbital approaches, and also to indicate the need for the use of a more sophisticated molecular orbital scheme than that adopted in this Introduction, i.e. one in which the a-framework of the rings is specifically included in the basis set as well as the rr-type orbitals. 

Fig. 22. Molecular Orbital Scheme for Mixed Sandwich Compounds.

One can visualize the effects of covalence on magnetic properties using a simple molecular orbital scheme. In the usual notation the orbitals considered for the transition metal M and the ligand X are ... 

Fig. 13. Molecular orbital scheme for octahedral fluoride complexes...

As metal atoms interact with nearest neighbors at relatively short distance, orbital overlap results in electron density being shared. As mentioned earlier, that electron density is delocalized in orbitals that are essentially molecular orbitals encompassing all of the atoms. The number of atoms that contribute an orbital to the molecular orbital scheme approaches the number of atoms present. As two atoms... 

On a more qualitative level, the bonding in the more stable isomer lb can be explained on the basis of the general molecular orbital scheme for bent (C2v) metallocenes containing 14 valence electrons, as shown in Fig. 5. The localization of three electron pairs in bonding orbitals (lal, 2 i, 2b2) is primarily responsible for the Si-Cp interaction the absence of a silicon orbital of a2 symmetry imposes the presence of a ligand-based non-bonding orbital. Structural adjustment from D5d (ferrocene type) to C2v... 

A simple molecular orbital scheme showing why p-oxo dimer formation is more likely to happen for Fe(III), d5, than for Co(III), d6, is shown in Figure 4.15. For d6 Co(III), the last electron goes into a 71 antibonding orbital, making reactions 4.16 and 4.17 less likely. 

Figure 4.15 Molecular orbital scheme for (A) Fe(III)-02 and (B) Co(III)-02 (Adapted with permission from Figure 4.15 of Jameson, G. B. Ibers, J. A., in Bertini, I. Gray, H. Lippard, S. J. Valentine, J. S. Bioinorganic Chemistry, University Science Books, Sausalito, CA, 1994.)...

Photooxidation and photoreduction of an electron donor and an electron acceptor, respectively, as illustrated schematically with a one-electron molecular orbital scheme. 

Fig. 5. The molecular orbital scheme for d square planar transition metal complexes.

Although Taube s pyrazine Ru"—Ru dimer was produced by the Ag oxidation of [(NHjljRu—NC4H4N—Ru(NH3)5] , attempts to prepare similar Ru"-Ru " complexes from [(NH3)5Ru(C5H4N)2Ru(NH3)5]" and [(NHjljRu—NC5H4C2H4C5H4N—Ru(NH3)5]" were unsuccessful. Cyclic voltammetric data indicated a two-electron oxidation to Ru" -Ru " dimers. In view of the identical ligands around each Ru atom, Mayoh and Day have questioned the localization of the Ru valencies in Taube s dimer into discrete Ru" and Ru " centres. However, a theoretical calculation of the conditions necessary for valence trapping in any mixed valence system, showed that the condition is indeed satisfied by the above Ru compound. Other workers have suggested that the available data on this complex could also be explained by a molecular orbital scheme in which the Ru ion and pyrazine-filled n (or k ) molecular orbitals are mixed, and the unpaired electron is mainly but un-symmetrically shared by the two cations. ... 

The triangular planar (D3h symmetry) CO/ molecular ion with 24 electrons (AB324-type) in CaC03 is easily ionized by radiation to electron and hole centres self-trapped in the lattice or an oxygen vacancy type C02 molecular ion at the anon site. Molecular orbital schemes based on the general scheme of AB3 molecules with 25,24 and 23 electrons for atoms A (B, C, Si, N, P, As and S) and B (O) characterize their specific -factor. Hence, the anisotropic -factor of these radicals estimated from the powder spectrum has been to identify the radical species.1... 

Such matters can be represented in a different way in terms of the d-electron configuration of transition metal ions in a molecular orbital scheme (Fig. 7.113). 

A recent paper (77a) has described the electronic spectra of a series of dicyclopentadienyl-metal halides [(C5H5)2MX2] in terms of a molecular-orbital scheme. 

Similarly, dibenzene chromium and its cation give moments which are in agreement with the simple molecular orbital scheme, viz.,... 

AsPh4]2[Mo S2C2(CN)2 3] was fitted by an axially symmetric spin Hamiltonian with g, = 2.000, g l = 1.974, Att = 10 G and AL = -100 G, interpreted in terms of a 1A1 ground state in D3 symmetry.49 The unpaired electron has predominantly metal dzi character. A molecular orbital scheme (Figure 4) was proposed for the dithiolene complexes.35 This scheme has been used in the discussion of ESR results,49 and electronic and resonance-Raman spectra.34... 

Although Cotton s molecular orbital scheme was largely qualitative, based on an approach involving a combination of atomic orbitals, a variety of theoretical studies... 

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