Structural Characterization of the Rhenium(V) Oxo Complex of Mercaptoacetyltriglyclne in its Dianionic Form

Abstract

Dianionic [MO(MAG₃)]²⁻(MAG₃ = penta-anionic form of mercaptoacetyltriglycine, M = ¹⁸⁶Re, ^99mTc) complexes have important applications in nuclear medicine. In vivo the complexes have a deprotonated carboxyl group that is important to their biodistribution. The solid-state structures of ⁹⁹Tc and Re complexes with mercaptoacetyltriglycine reported previously are monoanions with protonated carboxyl groups. In the present work, we report the preparation and X-ray crystal structure of Na₂[ReO(MAG₃)]·5H₂O (1), which contains the physiologically relevant dianion. The dianion is a distorted square pyramid with the nitrogen and sulphur donor atoms forming the base and the oxo ligand at the apex. The terminal carboxyl group is deprotonated, uncoordinated and has a syn orientation with respect to the oxo ligand. The syn conformation of the dianion in 1 differs in conformation from the anti-monoanion in [Bu₄N][ReO(MAG₃H)] but is similar to the syn-monoanion in [Ph₄P][⁹⁹TcO(MAG₃ H)].

Full Text

The Full Text of this article is available as a PDF (771.6 KB).