Formation Involving Unsubstituted Metal Ions Multidentate Ligand Substitution

Complex Formation Involving Unsubstituted Metal Ions Multidentate Ligand Substitution 

Crown Ethers, Cryptands, Catenands, Antibiotics, and Similar Ligands 

Kinetic studies of crown ether complexes reveal considerable mechanistic variety arising from variation in the nature of the metal ion, the crown ether, the anion, and the solvent. Thus a Cs NMR study of Cs exchange in [Cs(DA18C6)] (DA18C6 = 4,7,13,16-tetraoxa-l,10-diazaoctadecane) in nitromethane [see equation (8)] shows the exchange process to occur through a bimolecular mechanism 

A very interesting result is obtained in a ID and 2D NMR study of ligand exchange in the sandwich complex [Co(12C4)2] shown in equation (10). Conventional ID lineshape analysis of the resonances of 12C4 yields k 3S3.2 K) = 105 s = 102 kJ mor and AS = 57 J moP for intermolecular 12C4 

Ultrasonic studies of the complexation of Li by 12C4 and other crown ethers in 1,3-dioxalane are consistent with the Eigen-Winkler mechanism given in equation (11), where Li is only partially complexed in Li 12C4 and complexation 

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