Synthesis and structural determination of mononuclear nine-coordinate (EnH2)[YbIII(Egta)(H2O)]2 · 6H2O and [YbIII(Eg3a)(H2O)2] · 6H2O

Two novel rare earth metal coordination complexes, (EnH2)[YbIII(Egta)(H2O)]2 · 6H2O (I) and [YbIII(Eg3a)(H2O)2] · 6H2O (II), where En = ethylenediamine, H4Egta = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′,N′-tetraacetic acid and H3Eg3a = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′-triacetic acid, have been successfully synthesized through direct heating reflux and natural transformation. Complexes I, II were characterized by single-crystal X-ray diffraction techniques (CIF files CCDC nos. 966211 (I) and 966210 (II)). X-ray diffraction reveals that I is a nine-coordinate structure with a monocapped square antiprism crystallizing in the monoclinic crystal system with P21/c space group. The cell dimensionsare: a = 12.9616(14) Å, b = 12.7134(13) Å, c = 15.0132(15) Å, β = 105.3720(10)° and V = 2385.5(4) Å3. Complex II is also mononuclear nine-coordinate and crystallizes in the monoclinic crystal system with space group P21/c. The cell dimensions are as follows: a = 9.1926(10), b = 10.0046(12), c = 23.536(2) Å, β = 98.9650(10)° and V = 2385.5(4) Å3. However, when I is continued to direct heating reflux, the octadentate Egta ligand losts an acetic acid group and becomes a heptadentate Eg3a ligand. Thus, II was obtained, which was confirmed by means of single crystal X-ray diffraction analysis. This finding may offer a fast and efficient one-step reaction synthesis method of asymmetric aminopolycarboxylic acid.