Organomagnesates from Reactions of Dialkylmagnesium Compounds with Alkali-Metal Alkoxides, Potassium Hydride, and Other Salts

Reactions of R 2 Mg and KOR‘ in benzene form solutions containing organomagnesates that incorporate equal amounts of the reactants. NMR spectra of preparations in which the choice of R and R‘ leads to stereoisomers are consistent with a dimeric organomagnesate structure in which the magnesium atoms of two R 2 Mg units are bridged by the oxygen atoms of two OR‘ groups. Similar species result when NaOR‘ is the salt or diethyl ether is the solvent. When less than 1 equiv of KOR‘ is used, other species also are present. Reactions in benzene of R 2 Mg with some other salts, including tetrabutylammonium halides and LiNR‘ 2 compounds, also furnish 1:1 organomagnesates, but reactions with KH can lead to solutions of R 3 MgK.