THE EFFECTS OF COUNTERION AND SOLVENT ON THE REACTIVITY OF NICKEL ACYLATE COMPLEXES

Nickel acylate complexes, which can be generated starting with a carbon, nitrogen or oxygen nucleophile, act as acyl anion equivalents and therefore are an excellent method of assembling complex organic molecules from readily available starting materials. In an effort to increase the synthetic utility of these easily formed reagents, a systematic study of the reactivity of the nickel acylate complex generated under a variety of conditions was performed. Those acylate complexes generated with a carbon based nucleophile, such as a butyl or phenyl anion, show a large change in reactivity upon changing, for example, the solvent from THF to Et2O or the counterion from Li+ to MgCl+. This reactivity change is due to a large change in the structure of the acylate complex with a different counterion or solvent, as determined by IR and C-13 NMR spectroscopy and by oxidation potentials. In contrast, when a heteroatom nucleophile is used, such as a dialkyl amide or an alkoxide, the effect of a change in solvent or counterion on the structure, and therefore on the reactivity of the acylate complex, is minimal.