Coordination compounds polydentate

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... 

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) ... 

MONONUCLEAR COORDINATION COMPOUNDS WITH POLYDENTATE LIGANDS... 

Mononuclear coordination compounds with polydentate ligands 512... 

As seen in Subsection 5.2.1, bonds of ultrafine metal particles with oxide supports may become as strong as metal-ligand bonds in common coordination compounds. This happens, in particular, when the support exhibits defect surface sites that are notably more active than the sites on regular, defect-free parts of the surface. Then the question arises if one really can invoke the analogy of metal-ligand and metal-surface interactions. In other words, is the concept of a surface site as a polydentate ligand justified We addressed this noteworthy issue for an organometallic surface complex [183]. 

The trimethylaluminum complexes of tetraaza macrocycles contain AlMe2 groups and externally coordinated AlMes molecules [416-419] tetrathia macro-cycles [420, 421] are perhaps better described as simple coordination compounds of polydentate ligands, rather than host-guest complexes. This is suggested by the short Al-N distances (ca 2.0 A) and the external coordination of the metal. 

N.V. CJerbeleu, Transition Metal Coordination Compounds with Polydentate Ligands Ba.sed on Thio- And Selenosemicarbazide, D.Sc. Dissertation, Moscow, 1973 (Russ.). 

Observations on the chelate effect and, in particular, the importance of ring size, enable predictions to be made concerning the formation of stable coordination compounds with polydentate ligands that contain a variety of individual functional groups. Work on the synthesis of organic ligands... 

Coordination compounds formed by hard and charged donors with lanthanides, like those of d- and s-block metal ions, are usually thermodynamically stable — especially if coordinated by chelating ligands. Table 9.1 shows a comparison of thermodynamic constants for some key polydentate ligand systems in common with lanthanides. 

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