BERYLLIUM CHELATION BY DICARBOXYLIC-ACIDS IN AQUEOUS-SOLUTION

Maleic and phthalic acids are found to react with Be(OH)(2), generated in situ from BeSO4(aq) and Ba(OH)(2)(aq), in aqueous solution at pH 3 .0 or 4.4, respectively (25 degrees C), to give solutions containing t he complexes (H2O)(2)Be[(OOCCH)(2)] (1) and (H2O)(2)Be[(OOC)(2)C6H4] ( 3). The products can be isolated in high yield and identified by micro analytical data. With 2 equiv of the dicarboxylic acids and the pH adj usted to 5.5 and 5.9, respectively, by addition of ammonia, the bis-ch elate complexes [(NH4)(+)](2){[Be[(OOCCH)(2)](2)}(2-) (2) and [(NH4)()](2){Be[(OOC)(2)C6H4](2)}(2-) (4) are obtained, which can also be iso lated. The compounds show distinct Be-9, H-1, and C-13 resonances in t heir NMR spectra in aqueous solutions. Layering of an aqueous solution of compound 4 with acetone at ambient temperature reads to the precip itation of single crystals suitable for an X-ray structure determinati on. This salt (5) was found to contain the bis-chelated dianion {Be[(O OC)(2)C6H4](2)}(2-) with the beryllium atom in the spiro center of two seven-membered rings and an overall geometry approaching closely Ct s ymmetry. These anions are associated with two crystallographically ind ependent but structurally similar counterions [MeC(O)CH2CMe2NH3](+), w hich are the product of a condensation reaction of the ammonium cation with the acetone solvent. In the crystal the ammonium hydrogen atoms of the cations form N-H ... O hydrogen bonds with the oxo functions of the dianion.