Vanadium has been recognized to play important roles in biological systems. 1 Recently it is reported that bis(maltolato)oxovanadium(IV) complex is a potent insulin mimic agent.2,3 The structure, stability and lability of vanadium(V) compounds are important to the mechanisms by which these compounds act in biological systems and in part have contributed to the mechanisms by which vanadate mimics insulin action. 4 But the chemistry of vanadium has not much known yet. Of the representative vanadium(V) complexes, the crystal structures of vanadium(V) complexes with oxalate (Ox), 5,6 ethylenediaminetetraacetate (EDTA), 7,8 nitrilotriacetate (NTA), 9 and N-(2-hydroxyethylimino)diacetate 10 ligands have been studied by X-ray crystallography. Vanadium(V)-EDTA complexes are confirmed to have a α-cis structure (1), in which the anion has an irregular octahedral geometry with VO 2 core. But ethylenediaminediacetate (EDDA) is known to form a β-cis structure (2) with vanadium(V). 11 According to the solution studies, 11,12 EDDA forms α-cis and β-cis isomers with vanadium(V) while EDTA forms only the α-cis isomer with vanadium(V). The steric hindrance makes stable the α-cis form of the isomers because the substitution of an acetate group on nitrogen increases steric bulk.In this paper we report the synthesis of a new vanadium (V) complex, triammonium (propylenediaminetetraacetato)-dioxovanadate(V) monohydrate, as well as its crystal structure determined by X-ray crystallography. Propylenediaminetetraacetate (PDTA) is similar to EDTA in structure. PDTA has an asymmetric carbon on ethylenic backbone according to the substitution of a methyl group, while EDTA has a symmetric structure.
Experimental SectionMaterials. All reagent grade chemicals were used without further purification. Ammonium metavanadate (NH 4 VO 3 ) and propylenediaminetetraacetic acid (H 4 PDTA) were purchased from Aldrich Chemical Company.Preparation of vanadium(V) complex. The reaction of NH 4 VO 3 (0.02 mole, 2.34 g), H 4 PDTA (0.02 mole, 6.13 g) and 25% ammonia water (0.03 mole, 2.0 mL) in 100 mL water produced a yellow solution which was concentrated by passing a stream of dry air at room temperature. Ethanol was added and the resulting solution was kept in a refrigerator. The pale yellow crystals were formed and then filtered. The yield was 30%. The single crystals were obtained by dissolving the powders in water and keeping the solution in a refrigerator for several days. The chemical formula, VN 5 O 11 -C 11 H 28 , of the complex was obtained from the elemental analysis. Analytical data (%) are in the range of good agreement (calculated: C, 28.89; H, 6.17; N, 15.32. found: C, 28.83; H, 6.10; N, 15.26).X-Ray measurements. Preliminary experiments and data collection for X-ray crystal structure determination were performed on a Enraf-Nonius CAD4/Turbo diffractometer using Mo K α radiation (λ = 0.71069 Å). A small single crystal, 0.5 × 0.5 × 0.5 mm, was glued to a glass fiber with an epoxy resin. 25 reflections in the diverse reciprocal space were center...