Polydentate ligands definition

This definition is framed to emphasise the metal-binding properties of the ligands and includes most cyclic polydentate ligands that can incorporate a metal ion into the middle of a bonding cavity. It is also worth noting that many macrocyclic ligands have trivial names. This reflects the unfriendly nature of the systematic names for example, the systematic names of 6.5 and 6.8 are 1,4,8,11-tetraazatetracyclodecane and 2,5,8,15,18,2l-hexaoxatricyclo[20.4.0.09 14]hexacosa-l(22),8,11,13,23,24-hexaene, respectively. 

Despite the implication for Cu 02 species from these studies and a few other initial reports of possible Cu202 complexes using polydentate ligands [3,6,100], it was not until the mid-1980s that well-characterized complexes (i.e., those having a definitive structure with intact O—0 bonds, based on vibrational investigations or an actual x-ray structure) were described. 

The type of metal complexes now discussed specifically involve compounds with a definite position of donor centers in relation to the metal center for instance 20 and 21, or the conformational nonrigid di- and polydentate ligands illustrated by 22 [112,113,117] ... 

It is anticipated that polydentate ligands will become increasingly important in studies of catalysis, particularly for definition of the stoichiometry and stereochemical specificity of active species. Increasing use of polyphosphorus ligands can also be expected, since nmr spectra... 

All ligands can also be broadly classified as monodentate or as chelate depending on whether the ligand occupies one or more coordination sites of a single metal atom. A chelating ligand by definition is polydentate and is called bi-, tri-, or tetradentate depending on the number of coordination sites it occupies. 

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