D-block metal complexes

Figure 1.8 Molecular orbital diagram for an octahedral d-block metal complex ML6. The vertical arrows indicate different types of electron transition that may be brought about by photon absorption...

In a free d-block atom, all five d-orbitals are degenerate (all five have the same energy) but this is not the case in d-block metal complexes. In the octahedral complex [Ti(H20)6]2+, the five d-orbitals on the titanium are split into two sets a triply-degenerate, lower-energy set (t2g) and a doubly-degenerate, higher-energy set (eg). 

Chromatography cyclophosphazenes, 21 46, 59 technetium, 11 48-49 Chromites, as spinel structures, 2 30 Chromium, see Tetranuclear d-block metal complexes, chromium acetylene complexes of, 4 104 alkoxides, 26 276-283 bimetallics, 26 328 dimeric cyclopentdienyl, 26 282-283 divalent complexes, 26 282 nitrosyls, 26 280-281 trivalent complexes, 26 276-280 adamantoxides, 26 320 di(/ >rt-butyl)methoxides, 26 321-325 electronic spectra, 26 277-279 isocyanate insertion, 26 280 substitution reactions, 26 278-279 [9]aneS, complexes, 35 11 atom... 

Rare earth coordination chemistry has many characteristic properties compared with d-block metal complexes. Four main issues will be discussed in this section the valence state, chemical bonding, the coordination number, and the tetra effect - the changing gradation rules in rare earth coordination chemistry. 

Influence of ring size on the stability of first-row d-block metal complexes five-membered saturated rings are more stable. The exception is for chelation of unsaturated conjugated ligands, where six-membered rings (such as the acetylacetonate ligand illustrated) form complexes of enhanced stability. 

Like N2, P4 can act as a ligand in d-block metal complexes. Examples of different coordination modes of P4 are shown in structures 14.11-14.13. 

Bonding in d-block metal complexes valence Bonding in d-block metal complexes molecular... 

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 d-block metal complexes by using molecular orbital theory, it is incorrect to state that ligand field theory is simply the application of MO theory. ... 

A characteristic feature of many d-block metal complexes is their colours, which arise because they absorb light in the visible region (see Figure 20.4). Studies of electronic spectra of metal complexes provide information about structure and bonding, although interpretation of the spectra is not always straightforward. Absorptions arise from transitions between electronic energy levels ... 

Table 20.10 Overall stability constants for selected high-spin d-block metal complexes.

G. Frenking (2001) Journal of Organometallic Chemistry, vol. 635, p. 9 - An assessment of the bonding in d-block metal complexes including carbonyls which considers the relative importance of a and tt, as well as electrostatic, contributions to the metal-ligand bonds. 

Chapter 25 d-Block metal complexes reaction mechanisms... 

Carr. J.D. Coles. S.J. Hursthouse, M.B. Tucker, J.H.R. The effect of d-block metal complexation on the spectroscopic and redox properties of ferrocene derivatives containing pyridine ligands. J. Organomet. Chem. 2001. 637-639. 304-310. 

Suggest why (a) high coordination numbers are not usual for first row d-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 d-block metal complexes, high oxidation states are stabilized by fluoro or oxo ligands. 

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