Multidentate chelating ligands

Three- and four-coordinated Cu(I) compounds are most common however, many one-and two-coordinated Cu(I) ones are also known -. When less than four donor atoms are bound to the copper(I) ion the mononuclear copper(I) enolates tend to oligomerize. To preserve the volatility of the precursors, the oligomerization must be prevented, for example, by using bulky and/or multidentate chelating ligands. In Table 4, Cu(I) enolate coordination compounds which can be used as precursors for CVD of copper are listed. 

The substitution of [Tc02(py)4]" in DMF or DMF/MeOH mixtures with monodentate ligands such as cyanide, imidazole, or multidentate chelators such as cyclam and en has been studied. For all the ligands, complete replacement of the pyridines occurs. A dependence on the added alcohol is observed, whereas there is little or no dependence on the nature of the incoming ligand. The... 

Until recently only complexes of low stability were known for AC s even in the case of anionic chelating ligands (especially in water Table 7). Numerous and much more stable chelate complexes of AEC s with multidentate anionic ligands are known however (see Table 7). The complexation constants (3) always follow the stability sequence Ca2+ > Sr2+, Ba2+ and are in general difficult to modify in a progressive, stepwise fashion. It is obviously of interest to be able to control both stability and selectivity of AC and AEC complexes, especially the former. 

A wide range of multidentate amine ligands coordinate to platinum. The conformational analysis of chelate ring systems by NMR has been reviewed by Hawkins, and platinum complexes are included in this work.959 Amine ligands with sulfur groups can also act as chelates, and this subject has also been reviewed.960... 

The main use of ligand reactions in synthesis is in the construction of multidentate chelates. In this manner, the field of coordination chemistry has been enriched, as the development of new ligands has led to the introduction of new influences in metal ions. The various properties of coordination compounds are considered elsewhere in this book, but this chapter will focus attention on the synthesis of new ligands and complexes as a consequence of ligand reactions. 

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