Rf block metal complexes

Vanadium, tetranuclear rf-block metal complexes, 274-275 van der Waals surfaces cytochrome c, 106 heme peroxidases, 112-113 lignin peroxidase, 103 Van Vleck equation, 265, 268, 272, 287 Vector coupling, 264... 

Suggest why (a) high coordination numbers are not usual for first row fi -block metals, (b) in early d-block metal complexes the combination of a high oxidation state and high coordination number is common, and (c) in first row rf-block metal complexes, high oxidation states are stabilized by fluorido or oxido ligands. 

In this chapter, we discuss complexes of the tZ-block metals and consider bcmding theories that rationalize experimental facts such as electronic spectra and magnetic properties. Most of the discussion centres on first row rf-block metals, for which theories of bonding are most successful. The bonding in rf-block metal complexes is not fundamentally different from that in other compounds, and we shall show applications of valence bond theory, the electrostatic model and molecular orbital theory. 

Although VB theory (see Sections 2.1, 2.2 and 5.2) in the form developed by Pauling in the 1930s is not much used now in discussing rf-block metal complexes, the... 

Table 20.2 Values of for some rf-block metal complexes.

Ligand field, like crystal field, theory is confined to the role of d orbitals, but unlike the crystal field model, the ligand field approach is not a purely electrostatic model. It is a freely parameterized model, and uses and Racah parameters (to which we return later) which are obtained from electronic spectroscopic (i.e. experimental) data. Most importantly, although (as we showed in the last section) it is possible to approach the bonding in rf-block metal complexes by using molecular orbital theory, it is incorrect to state that ligand field theory is simply the application of MO theory. ... 

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