Novel TcP3X3 (X=S, O) cores in Tc(III) chemistry

In recent years we devoted most of our research efforts in developing Tc chemistry with bidentate functionalized phosphines because of their ability to act both as reducing and coordinating agents [2]. These functionalized phosphines contain a P(III) atom that can easily reduce the pertechnetate ion and stabilize the metal in lower oxidation states by means of its pi-backbonding together with the chelation of the whole ligand. In this field encouraging results have been obtained with phosphino-carboxylic derivatives of the type Ph (R=o-C6H4, C2H4, CH2 (abbreviated as P-COOH) [3] and more recently with the ligand (2-diphenylphosphino)benzeneamine (abbr. PNH2 [4]. In both cases, Tc(III) complexes of the type Tc(P-X)3 (X=COO-, NH-) have been obtained, the three mono-negative bidentate ligands being coordi nated around the metal in a meridional configuration. The above mentioned ‘reducing-coordinating’ approach has allowed the synthesis of a class of Tc(III) complexes utilizing the tris(o-thiophenyl)phosphine, a tetradentate ‘umbrella shaped’ ligand. Either octahedral or trigonal bipyramidal geometries have been observed for the resulting complexes, depending on the con centration of the ancillary isonitrile ligand [5].In this context we now report on the reaction of pertechnetate with the two bidentate functionalized phosphines, (2-diphenylphosphino)thiophenol (abbr. P-SH) and (2-diphenylphosphino)phenol (abbr. P-OH) with the aim of looking at the molecular structure of the resulting complexes and to confirm the favourable reducing and coordinating properties of such a class of ligands towards technetium. The synthesis and characterization (including X-ray structure) of the resulting Tc(III)(P-S)3 (1) and Tc(III)(P-O)3 (2) complexes are reported here.