The complexation of rhodium(iii) with acyclic diaminedithioether (DADTE) ligands

Abstract

¹⁰³Rhodium(III) complexes derived from seven acyclic tetradentate N₂S₂ ligands (one diaminedithiol and six diaminedithioether ligands) have been synthesized and characterized. Structural variations in the ligand include the length of carbon backbone between the coordinating atoms (222; 232; 323; 333), the presence or absence of gem-dimethyl groups α to sulfur, and the nature of the organic moiety on the sulfurs (hydrogen, p-methoxybenzyl and methyl). For each ligand, the formation of cis and/or trans dichloro isomeric complexes was assessed. Two complexes have been further characterized by single crystal X-ray diffraction. Preparation of the ¹⁰³Rhodium(III) complexes was conducted and overall radiochemical yields, in vitro stability and log D_7.4 values were measured. From these studies, the ligand with the 232 chain length, gem-dimethyl groups and the methyl thioether (L4) emerged as a preferred ligand for formation of rhodium complexes with trans geometry and highest radiochemical yields.