Multidentate chelate

H02CCH2)2N-CH2 CH2-N(CH2C02H)2-An important compound, which owes its use to its sequestering properties. A multidentate chelating agent. Forms complexes with most elements. 

Simple monodentate NHCs are somewhat susceptible to dissociation when coordinated to early transition metals [6], so in most cases multidentate chelating hgands are employed in which the carbene is tethered to a strongly coordinating anchoring group. This is not universally the case however, and simple monodentate NHC complexes of Zr 1 (Fig. 4.1) have been studied [7]. The complexes were activated with MAO and tested for ethylene polymerisation, leading to moderate activities between 7 and 75 kg mol bar h for linear polyethylene. 

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... 

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. 

Favourable entropic effect generated by a multidentate chelating agent with respect to the complexation by monodentate 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. 

ANKB-33 resin is an iminodiacetic acid exchanger this multidentate chelating functionality is capable of forming metal coordination complexes with different stabilities [10,31]. 

Fig. 2. First and second order rate constants for water substitution of the inner coordination sphere of Ni2+ and Cu + for a series of hgands. The values for simple ligands are corrected to yield the first order rate constants of substitution, whereas overall constants are given for multidentate chelates (values from ref. 2)...

---