Conformation of chelate rings

The results suggest that the five-membered peptide chelate ring, in which the atoms are nearly coplanar, may be more subject to steric effects than is the case for the gauche conformation of chelate rings of ethylenediamine and its C-methyl derivatives. However, the corresponding nucleophilic displacement reactions have not been studied and it is too early to draw... 

Ligand Complex- configuration2) Ni N43) N73) n10 c2 c3 Cs c6 C8 C94) Conformation of chelate rings NjN4 n4n7 n7n10 Ref. 

Stereoisomers include cis and trans isomers, chiral isomers, compounds with different conformations of chelate rings, and other isomers that differ only in the geometry of attachment to the metal ion. As mentioned at the beginning of this chapter, study of stereoisomers provided much of the experimental evidence used by Werner to develop and defend his coordination theory. Similar study of new compounds is useful in establishing structures and reactions, even though development of experimental methods such as automated X-ray diffraction can shorten the process considerably. 

IR-9.3.4.14 Application of the skew-lines convention to conformations of chelate rings... 

Figure IR-9.4. 8-Conformation of chelate rings (a) five-membered (b) six-membered.

Most CD spectral studies of cobalt(III) complexes have been undertaken to investigate various sources of optical activity such as distribution of chelate rings, conformation of chelate rings, vicinal effect due to asymmetric carbon in an optically active ligand, and vicinal effect due to an asymmetric donor atom. Extensive reviews on these subjects have been written by Fujita and Shimura (1), Hawkins (2), and Mason (3). 

A thorough analysis of the conformations of chelate rings was given in a classic paper by Corey and Bailar (22). The energy differences for various combinations of ligand conformations predicted from their treatment have been consistent with experimental results. 

Draw all geometrical isomers of [Co(trien)Cl2] ", where trien is the tetradentate ligand triethylenetetramine which may be conveniently represented by N-N-N-N in your drawings. Also, ignoring the conformation of chelate rings, identify the symmetry point group of each isomer and predict whether it is optically active or not. 

Certain effects observed in nmr spectra relate to the interconversion of equivalent or different conformations of chelate rings. For example, the low-temperature nmr spectrum of (-)-[Pd(diop)2], where diop is the well-known diphosphine 27, shows an AA BB spectrum which coalesces... 

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