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Alkylations and oxidations of nickel and zinc thiolate complexes
The aim of the work presented here was not only to synthesize novel models for zinc and nickel active sites, but also to further explore the reactivity of the metal thiolates. In cases where there was more than one sulfur donor in the ligand set, the influence of derivatizing one on the ability of the other(s) was explored. ^ The metal, the spin state, the varying donor environment, and steric factors were found to have a dramatic effect on the nucleophilic reactivity of thiolates towards S-alkylating reagents. All of the nickel complexes showed reactivity. The zinc complexes failed to react except for one neutral imine thiolate complex, which was found to react very slowly. Cationic complexes were found to react more slowly than the neutral complexes, and the neutral complexes react more slowly than the anionic complexes. ^ The oxidations of several neutral nickel and zinc dithiolate complexes were also studied in detail. An investigation of the oxygenation reaction of a high spin pentacoordinated alkylthiolate nickel complex, showed that the product was not the expected sulfur oxygenate, but a thiocarboxylate. Studies with a similar zinc iminothiolate complex gave analogous thiocarboxylate products, showing that the oxygenation products are thermodynamically determined by the ligand alone and not the metal center. ^ The oxidation studies presented contribute another more extensive and detailed series of sulfur oxygenates, to the family of low spin nickel dithiolate complexes that react with oxygen species. The isolation of a key intermediate in the sequential oxidation of a tetracoordinate nickel dithiolate provides an alternative route to the accepted mechanism for oxidation of dithiolate complexes. ^
Balwant Singh Chohan,
"Alkylations and oxidations of nickel and zinc thiolate complexes"
(January 1, 2002).
Electronic Doctoral Dissertations for UMass Amherst.