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

(103)Rhodium(III) complexes derived from seven acyclic tetradentate N(2)S(2) 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 alpha 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 (103)Rhodium(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.