Organomagnesates from reactions of dialkylmagnesium compounds with alkali-metal alkoxides, potassium hydride, and other salts

Reactions of R2Mg 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 R2Mg 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 R2Mg 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 R3MgK.