Multidenticity

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. 

There are a few documented examples of studies of ligand effects on hydrolysis reactions. Angelici et al." investigated the effect of a number of multidentate ligands on the copper(II) ion-catalysed hydrolysis of coordinated amino acid esters. The equilibrium constant for binding of the ester and the rate constant for the hydrolysis of the resulting complex both decrease in the presence of ligands. Similar conclusions have been reached by Hay and Morris, who studied the effect of ethylenediamine... 

Careful examination of literature reporting Lewis-acid catalysis of Diels-Alder reactions in combination with kinetic investigations indicate that bidentate (or multidentate) reactants are required in order to ensure efficient catalysis in water. Moreover, studies of a number of model dienophiles revealed that a potentially chelating character is not a guarantee for coordination and subsequent catalysis. Consequently extension of the scope in this direction does not seem feasible. 

Protonated and diprotonated carbonic acid and carbon dioxide may also have implications in biological carboxylation processes. Although behavior in highly acidic solvent systems cannot be extrapolated to in vivo conditions, related multidentate interactions at enzymatic sites are possible. 

Charge-charge repulsion effects in protolytically activating charged electrophiles certainly play a significant role, which must be overcome. Despite these effeets multidentate protolytic interactions with superacids can take plaee, increasing the electrophilie nature of varied reagents. 

The utility of complexation titrations improved following the introduction by Schwarzenbach, in 1945, of aminocarboxylic acids as multidentate ligands capable of forming stable 1 1 complexes with metal ions. The most widely used of these new ligands was ethylenediaminetetraacetic acid, EDTA, which forms strong 1 1 complexes with many metal ions. The first use of EDTA as a titrant occurred in... 

In recent years this simple picture has been completely transformed and it is now recognized that the alkali metals have a rich and extremely varied coordination chemistry which frequently transcends even that of the transition metals. The efflorescence is due to several factors such as the emerging molecular chemistry of lithium in particular, the imaginative use of bulky ligands, the burgeoning numbers of metal amides, alkoxides, enolates and organometallic compounds, and the exploitation of multidentate... 

Izatt, R. M., Christensen, J. J, (eds.) Synthetic Multidentate Macrocyclic Compounds, New York, Academic Press 1978... 

Multidentate ligands contain more than two coordinating atoms per molecule, e.g. 1,2-diaminoethanetetra-acetic acid (ethylenediaminetetra-acetic acid, EDTA),f which has two donor nitrogen atoms and four donor oxygen atoms in the molecule, can be hexadentate. 

The vast majority of complexation titrations are carried out using multidentate ligands such as EDTA or similar substances as the complexone. However, there are other more simple processes which also involve complexation using monodentate or bidentate ligands and which also serve to exemplify the nature of this type of titration. This is demonstrated in the determination outlined in Section 10.44. 

They demonstrate the sensitivity of the Ru—N bond length to the trans-donor atom and also how when a multidentate ligand is involved bond lengths do not necessarily shorten on increasing the oxidation state. 

Multidentate amines form many complexes with these metals. 

Certain multidentate ligands also provide for better solubility. Cu1 complexes formed with tctramcthylcthylcncdiaminc (TMEDA), N,N,N ,N ,N -pentamethyldiethylenetriamine (PMDETA, 140) and 1,1,4,7,10,10-hcxamethyltricthylcnctctraminc (HMTETA, 144) and Mc6TREN (145) have been found effective.311 Transfer to ligand during MMA polymerization has been reported as a side reaction when PMDETA is used. 12 313... 

Macropolycyclic ligands, 2,942 classification, 2,917 metal complexes binding sites, 2, 922 cavity size, 2,924 chirality, 2, 924 conformation, 2,923 dimensionality, 2, 924 electronic effects, 2, 922 shaping groups, 2,923 structural effects, 2,922 molecular cation complexes, 2,947 molecular neutral complexes, 2,952 multidentate, 2,915-953 nomenclature, 2,920 Macro tetrolide actins metal complexes, 2,973 Macrotricycles anionic complexes, 2,951 cylindrical... 

Multidentate Macrocyclic and Macropolycyclic Ligands 22 Ligands of Biological Importance... 

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