Reactivity of the [M(PS)(2)](+) Building Block (M = Re-III and Tc-99m(III); PS = Phosphinothiolate) toward Isopropylxanthate and Pyridine-2-thiolate

摘要

The coordination properties of isopropylxanthate (i-Pr-Tiox) and pyridine-2-thiolate (PyS) toward the [M(PS)(2)](+) moiety (M = Re and Tc-99m; PS = phosphinothiolate) were investigated. Synthesis and full characterization of [Re(PS2)(2)(i-Pr-Tiox)] (Re1), [Re(PSiso)(2)(i-Pr-Tiox)] (Re2), [Re(PS2)(2)(PyS)] (Re3), and [Re(PSiso)(2)(PyS)] (Re4), where PS2 = 2-(diphenylphosphino)ethanethiolate and PSiso = 2-(diisopropylphosphino)ethanethiolate, and the structural X-ray analysis of complex Re3 were carried out. Tc-99m analogues of complexes Re2 ((99m)Tc2) and Re4 ((99m)Tc4) were obtained in high radiochemical yield following a simple one-pot procedure. The chemical identity of the radiolabeled compounds was confirmed by chromatographic comparison with the corresponding rhenium complexes and by dual radio/UV HPLC analysis combined with ESI(+)-MS of 99g/Tc-99m complexes prepared in carrier-added conditions. The two radiolabeled complexes were stable with regard to trans chelation with cysteine, glutathione, and ethylenediaminotetraacetic acid and in rat and human sera. This study highlights the substitution-inert metal-fragment behavior of the [M(PS)(2)](+) framework, which reacts with suitable bidentate coligands to form stable hexacoordinated asymmetrical complexes. This feature makes it a promising platform on which to develop a new class of Re/Tc complexes that are potentially useful in radiopharmaceutical applications.