The present invention concerns an improved process for producing an ionomer from an acid group containing polymer. Production of the ionomer requires neutralization of an acid functionality or reaction of anhydride functional groups with a metal ion source to produce a salt. It has been found that metal hydrocarbyls or metal hydrides can be used as the source of metal ions for neutralizing the acid or anhydride functionalities. The reaction can occur in a solvent or in a melt, but is most preferably performed in a solvent.