Molecular orbital theory octahedral complexes

The molecular orbital theory as applied to octahedral and tetrahedral metal complexes. 

Crystal field theory was developed, in part, to explain the colors of transition-metal complexes. It was not completely successful, however. Its failure to predict trends in the optical absorption of a series of related compounds stimulated the development of ligand field and molecular orbital theories and their application in coordination chemistry. The colors of coordination complexes are due to the excitation of the d electrons from filled to empty d orbitals d-d transitions). In octahedral complexes, the electrons are excited from occupied t2g levels to empty Cg levels. The crystal field splitting Ao is measured directly from the optical absorption spectrum of the complex. The wavelength of the strongest absorption is called Amax and it is related to Ao as follows. E = hv, so Ao = hv = Because en-... 

We apply molecular orbital theory to octahedral coordination complexes just as we did for the simple metal carbonyl in Section 8.2. We begin by constructing the cr MOs from the valence d, s, and p orbitals of the central metal atom and the six ligand orbitals that point along the metal-ligand bond directions in an octahedral complex. In the case of the Cr complexes we use as examples, the relevant... 

The molecular orbital theory of complexes (6), developed out of crystal field theory (7) by the inclusion of both a- and sr-covalent interactions, has been successfully applied 8—13) to the octahedral (14. 15) carbonyls of the 4 metals (V i, Cr , Mn+ etc.). The qualitative discussion of this octahedral case is particularly simple because of a clean-cut separation (within the single-configuration approximation) of a- and ji-systems. 

Bosch, H., Viste, A., Gray, H. B. (1966) Molecular orbital theory for octahedral and tetrahedral complexes. J. Chem. Phys. 44, 10. 

A molecular orbital theory for octahedral / complexes is described. It is pointed out that the neglect of covalent bonding in the analysis of optical data for the actinide complexes is not justified, and that its inclusion leads to orbital reductions which are considerably greater than have usually been assumed. 

Chapter 20 Molecular orbital theory octahedral complexes 565... 

In Section 20.4, we apphed molecular orbital theory to octahedral complexes containing w-acceptor ligands and gave a rationale for the fact that low oxidation state organometallic complexes tend to obey the 18-electron rule. This rule often breaks down for early and late J-block metals as examples later in the chapter show 16-electron complexes are common for e.g. Rh(I), Ir(I), Pd(0) and Pt(0). The majority... 

The electronic configuration of elemental iron is ls 2s p 3s 3p 3d 4s or shortened to include the argon core as [Ar]3d 4s. Ferrous and ferric cations contain two and three fewer electrons, respectively, in the 4s and 3d orbitals. The molecular orbital theory of octahedral complexes dictates that iron can utilize up to nine orbitals (one s, three p, and five d) to form molecular orbitals resulting in iron-ligand bonds [1]. 

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