This invention concerns an improved process for preparing a hydrocarbon soluble dialkylmagnesium compound by reacting a dialkylmagnesium-magnesium chloride composition in an inert hydrocarbon solvent with a chemical selected from an alkali metal alkyl compound and an alkali metal trialkylmagnesiate compound and dialkylmagnesium compounds of the formulaMgR.sub.a R.sup.1.sub.b R.sup.2.sub.c R.sup.3.sub.d R.sup.4.sub.ewherein a+b+c+d=2, R is a 2-alkylsubstituted primary alkyl group and R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are hydrocarbyl groups which may be the same or different.