First Isolation of a Metal Ketyl in Aggregated Forms. X-ray Structures of Dimeric and Tetrameric Socliam Fluoreaone Ketyi Compieses:[Na(mu _2- eta~1-ketyl)(HMPA)_2]_2 and [Na(mu _3- eta~14-ketyl)(HMPA)]_4

摘要

Alkali metal ketyls, formed via one-electron redaction of. ketones or aldehydes, have been known since the last century. It was suggested on the basis of UV—vis and ESR spectra that these ketyls may exist in solution in an equilibrium between monomeric and dimeric forms. However, the isolation and structural characterization of these ketyls have never been achieved due to their high reactivity. Although several metal pinacolates have been isolated, only one ketyl has been described. Studies on thisketyl complex [(ArO)_2Sin(fiuorenone ketyl)(THF)_2 (Ar = 2,6-Bu_2-4-Me-C_6H_2)] showed that a Decrease in the static hindrance around the central metal by substitution of the THF ligands with Et_2O resulted in the immediate coupling of the ketyl to yield a pinacolate, rather than the formation of a dimeric ketyl.