Coordination compounds polydentate ligands

The behaviour of polydentate ligands containing sulphinyl groups has received much less attention. Giesbrecht and Osorio203 have reported the coordination compounds of bivalent transition metal (Mn2+, Co2+, Ni2+, Cu2 +, Cu2+, Zn2+) perchlorates with 2,2 -sulphinyldiethanol (SDE). 

The importance of metal coordination compounds in biological systems has led to the study of polydentate Schilf base complexes of cobalt(II), nickel(II), and copper(II) (204, 205). Dimers have been observed in the spectra of complexes of both tri- and tetradentate ligands [e.g., salicylaldehydeand A,A-bis(salicylidene)ethylenediamine]. The parent ions form the base peaks, and the spectra are characterized... 

An alternative strategy involves the use of polydentate ligands to prevent oligomerization by satisfying the coordination number of the metal center. To date, this strategy has proved the more successful of the two in that polydentate ligand adducts of Group 2 compounds are more frequently... 

This section describes the synthesis as well as chemical and physical properties of Group 2 metal /3-diketonate compounds that also contain coordinated polydentate ligands to prevent oligomerization. 

Overall, the formation of pentacoordinated complexes is favored by chelating and particularly by polydentate macrocyclic ligands. A search in the Cambridge Structural Database reveals that many of the structurally characterized five-coordinated Pd(II) compounds contain macrocyclic or rigid polydentate ligands, S, N, and P donor atoms being dominant. Complexes (23), (24) and (25) are typical examples. 

Neutral polydentate ligands are widely used for the synthesis of coordination compounds of transition metal ions. -i When different synthetic routes are possible for a given ligand, those which give the highest yields with the least number of steps and minimize the number of possible isomeric or by-products will obviously be preferred. The above criteria may be exemplified by a series of neutral tetradentate ligands of the tripod or umbrella type with a nitrogen atom as the top donor these may be described as 2-substituted triethylamine derivatives (I) ... 

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