COMPLEXATION OF BERYLLIUM(II) BY MALEIC AND SUCCINIC ACID

Beryllium succinate dihydrate [Be(C4H4O4)](H2O)(2) is formed in the re action of equimolar quantities of beryllium sulfate, succinic acid and barium hydroxide in aqueous solution at pH 3.2. Sodium, potassium, an d ammonium bis(succinato)beryllates M-2[Be(C4H4O4)(2)] are obtained us ing the same reagents in the molar ratio 1.2. 1 and adjusting the pH t o 6.3-6.5 with NaOH, KOH or concentrated aqueous ammonia, respectively . The corresponding potassium bis(maleato)beryllate is prepared simila rly and obtained as a crystalline monohydrate, the structure of which has been determined by X-ray methods. The lattice contains spiro-bicyc lic dianions with the Be atom chelated by two dicarboxylate ligands. T he compounds undergo slow hydrolysis in water as shown by time- and pH -dependent Be-9 NMR spectroscopy. In the neutral region (pH 6.5-6.9) t he maleinato complexes are in an equilibrium with trinuclear compounds M-3{[Be(C4H2O4)OH](3)} as the predominating species, while in acid so lution (at pH 1.3) only the aquo complex [Be(H2O)(4)](2+) remains. In the intermediate pH region various complexes of the above types coexis t, with only very slow ligand exchange (on the NMR time scale).