Tris(1,2-dimethyl-3-hydroxy-4(1H)-pyridone)oxotantalum(V): a new water-soluble tantalum complex containing the [Ta=O]3+ core

The synthesis, the characterization and the X-ray crystal structure of a novel tantalum(V) complex tris(1,2-dimethyl-3-hydroxy-4(1H)-pyridone)oxotantalum(V) [TaO(C7H8O2N)3] 1 is reported. Starting from the tantalum pentaethoxide a two-step reaction was carried out observing rigorous anhydrous conditions in methanol in the first step, while the insertion of the oxo group was achieved using water as oxygen donor in the second step. X-Ray diffraction analysis of a crystal of 1 obtained upon evaporation of an aqueous solution shows a seven-coordinate monomeric complex containing the [Ta=O]3+ core in the triclinic space group P¯1, a = 7.282(3), b = 14.055(5), c = 16.987(6)A˚ , a = 65.704(5), b = 89.155(6), c = 75.270(6)◦, V = 1525(1)A˚ 3, Z = 2. Spectroscopic investigation reveals that the complex is highly soluble and stable in water at physiological pH values; as a consequence the complex may represent a potential candidate for the development of new studies on aqueous tantalum(V) chemistry for radiopharmaceutical applications.