Substitution reactions of chelates

Most of the information on the substitution reactions of chelated organic ligands has been obtained by Collman and co-workers, who have... 

The kinetics and mechanisms of substitution reactions of metal complexes are discussed with emphasis on factors affecting the reactions of chelates and multidentate ligands. Evidence for associative mechanisms is reviewed. The substitution behavior of copper(III) and nickel(III) complexes is presented. Factors affecting the formation and dissociation rates of chelates are considered along with proton-transfer and nucleophilic substitution reactions of metal peptide complexes. The rate constants for the replacement of tripeptides from copper(II) by triethylene-... 

Substitution reactions of hexadentate diimine complexes of iron(II) are generally slow, thanks to the combination of the strongly binding diimine groups and the chelate effect, even when the ligand contains only two diimine units of the less strongly bonding py—CH=N— type k2(OH)... 

A similar study of the rates and mechanisms of substitution reactions of the Pt(II) 1,1-dithiolate complexes, Pt(L)2 (L = /-MNT2, NED2, CDC2 and CPD2-), also has been reported (352). The mechanism proposed for the substitution reactions of the Pt(L)2- complexes with bidentate 1,1-dithio chelates is the same as that shown in Fig. 60. 

Less expected, perhaps, are results on substitution reactions of four-coordinate nickel(II) chelate complexes which occur in equilibrium between planar and tetrahedral isomers. Despite the longer bond lengths of the tetrahedral isomers, it is the planar isomers which undergo the substitution reactions (140). 

The C-2 selective nucleophilic substitution reactions of 2,3-epoxy alcohols mediated by trialkyl borates the first endo-mode epoxideopening reaction through an intramolecular metal chelate. Org. Lett. 2003, 5, 1789-1791. 381... 

Much of what is currently known about substitution reactions of square planar complexes came from a lar e number of careful studies executed in the I960s and I970S.3 You should not conclude, however, that details of the mechanisms of these I eactions are of historical intei est only. Work in this area continues unabated as studies focus on chelation, steric effects, biological i eactions. and homogeneous catalysts. For example, the mechanism for the Wacker process (Chapter 15), which utilizes squai e planar [PdCl ] as a homogeneous catalyst for the industrial conversion of ethylene to acetaldehyde, is still a subject of investigation. The overall reaction for the process is ... 

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