Some t-butylmagnesium and related complexes. Reactions between hydrides and organomagnesium compounds
Solutions of di-t-butylmagnesium have been prepared by the dioxan precipitation method, and from them several dibutylmagnesium complexes have been obtained. These include But2Mg–dioxan, which is insoluble in toluene and soluble in ether, the bistetrahydrofuran complex which is partly dissociated in benzene, and the tetramethylethylenediamine complex. Reaction between trimethylethylenediamine and Pri2Mg and But2Mg gives (PriMgNMeC2H4NMe2)2 and (ButMgNMeC2H4NMe2)2, the latter being slightly dissociated in benzene. Pyrolysis of these compounds leads to alkane, not alkene, evolution.
Reactions between diethylmagnesium and alkali-metal hydrides either do not take place or result in attack on the solvent. Butyl-lithium gives LiBunMe2Mg,OEt2 on reaction with dimethylmagnesium in ether, but pyrolysis of this gives dimethylmagnesium and lithium hydride. Exchange reactions between sodium trialkylborohydrides and some alkylmagnesium compounds result in the precipitation of magnesium hydride containing occluded alkyl groups.
The solid Grignard reagent, (ButMgClOEt2)2, is dimeric in benzene, and is believed to contain chlorine bridges.