Neutral W(V) Complexes Featuring the W2O2(µ-O)2 Core and Amino Acids or EDTA Derivatives as Ligands: Synthesis and Structural Characterization

Abstract

Multinuclear complexes of heavy metals, such as tungsten, have demonstrated considerable potential as candidates for advanced radiocontrast agents. Of particular interest is the development of stable non-ionic compounds with high metal content and reasonably low osmolality in solution. Accordingly, we have synthesized a series of neutral W(V) complexes that contain the W2O2(µ-O)2 core and amino acids or disubstituted EDTA derivatives as ligands. The compounds were prepared from the oxalatotungstate(V) complex via a convenient procedure utilizing microwave heating. Their detailed characterization was accomplished by electrospray ionization high-resolution mass spectrometry (ESI-HRMS), 1H and 13C NMR spectroscopy, elemental analysis, and X-ray crystallography. Further experiments to evaluate the utility of the complexes as radiocontrast media were precluded by their poor aqueous solubility.