Oxygen liganding system

In summary, the fragmentary evidence at hand suggests that sulfur was the primordial iron complexing material and that this ligand system was selectively modified by stepwise transition to a mixed sulfur-nitrogen and sulfur-oxygen and, finally, to an all-oxygen type of coordination. 

Another ligand system, bis[2-(2-pyridyl)ethyl]amine (PY2) having a (CH2) linker, was also prepared and studied.41a If n = 4, as shown in Figure 5.16, the ligand is called N4 that is, N4 = N 4PY2. Upon oxygenation, peroxo complexes would have the formula [Cu2(N4)(02)]2+ ... 

In reference 44 the authors found that the [Cu2(p-0)2]2+ core with either the LlPr3 or LBn3 ligand system will activate C-H bonds for cleavage and oxidation, again having important implications for oxygenation catalysis. These authors provide a useful summary for the two core structures, which are replicated in Table 5.7. 

In the course of the quest for new Fe(III) spin crossover compounds, systems related to N,N-disubstituted-dithiocarbamates have been explored. This section deals with oxygen and selenium derivatives of this parent ligand system, as displayed in Fig. 2. 

Fission of the ligand molecule may take place during the redox process of the metal-ligand system. This is generally true of systems in which the ligands are bound to the metal through an oxygen atom. 

This chapter is principally concerned with ligand systems which contain a carbon atom linked to two oxygen atoms. In the vast majority of the complexes to be considered the donor atom is the relatively small, less polarizable oxygen atom, i.e. hard under the Pearson classification. As a consequence these ligands are seldom found in conjunction with low oxidation state metals. Considerable advances have been made in this area in recent years. The most notable of these has been the work of Cotton, who has made extensive use of the ability of such ligands to bring metal... 

At the same time, this method has a series of disadvantages. Among them, we note the possibiity of contamination of the final product not only by the excess of one of the reactants [2], but also by complexes of the components of the ligand system. So, to carry out strictly template synthesis experiments, it is necessary to take into account a comparative stability of coordination compounds, obtained on the basis of initial components-precursors and the ligand itself. Not only the thermodynamic characteristics of complex-formation processes should be taken into consideration [326,327], but also the influence of solvolysis processes (especially hydrolysis) and the type of atmosphere (air oxygen). 

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