Coordination mixed ligand systems

Synthetic strategy toward a biotin derivative with fluorescence properties after coordination of a tridentate ligand to the [Re(CO)3] core (James et al. 2006a) and a [2+1] mixed ligand system (Lo and Hui 2005)... 

The complexes on surface of chelate-functionalized silica often include ligands available in solution in the coordination sphere. Use of a chromophore reagent as a ligand leads to the formation of colored mixed ligand complexes (MLC). The phenomena can be used as a basis for developing test-systems for visual determination of microquantities of inorganic cations in water. 

A detailed comparative study of the allylic substitution in allylacetates by amines has been carried ont for the two related mixed donor ligand systems 113 and 114 shown in Fig. 2.19. The P-C system shows dramatically lower activity than N-P, which has been atlribnted to the decreased electrophiUcity of the coordinated aUyl gronp, originating from the strongly o-donating NHC and P donors, compared to N and P donors. 

A number of mixed crown ligands have been synthesized combining N, O, or S ligands. The larger, more flexible, ligand systems can show interesting coordination patterns as the zinc binds to its preferred donor set. 

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. 

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