The process of this invention for preparing Mn(II) chelate comprises forming the Mn(II) chelate by mixing manganese (II) oxide (insoluble) with an aqueous suspension comprising a molar equivalent or molar excess of the insoluble protonated chelating compound at a temperature of from 20.degree.to 50.degree. C. When the reaction is carried out with a protonated chelating agent in the absence of base, a precipitate of the protonated Mn(II) chelate is formed. A low osmolarity MN(II) chelate solution can be formed from the precipitates by dissolving them in an aqueous solution of base. When the initial chelate forming reaction is carried out in a solution containing a molar equivalent or excess of sodium hydroxide, a low osmolarity solution of the Mn(II) chelate is directly formed with most chelating agents. Preferred chelating compounds for this process include DPDP, DTPA, DCTA, EDTP, DOTA, DOXA, DO3A and EDTA. The Nm(II) chelate precipitates and low osmolarity solutions formed by the above processes are also aspects of this invention.