RHENIUM COMPLEXES STABILIZED BY TRIS-CHELATING OXYGEN LIGANDS - POTENTIAL NEW RADIOPHARMACA

Four new tris-chelating oxygen ligands of the general formula L- = [(C5H4R)Co{P(O)R'R"}3]-(R = COOCH3, COOH and R' = OCH3; R = H and R' = O(CH2)5COOCH3, O(CH2)5COOH; R" = OCH3) have been synthesized. These ligands L- and others of the same type have been used to prepare the rhenium oxo complexes [LReO3] and [LReOX2] (X = Cl, Br, I). In order to judge their use in radioimmunotherapy the corresponding complexes containing radioactive rhenium isotopes have also been synthesized. The rhenium(VII) as well as the diamagnetic rhenium(V) complexes are stable in air in the solid state as well as in organic solvents. They hydrolyze slowly in water to yield perrhenic acid. The X-ray structures of the sodium salt Na[(C5H4COOCH3)Co{P(O)(OCH3)2}3] and of the rhenium complex [LReOBr2] (R = H, R' = R" = OCH3) have been determined. The sodium salt crystallizes in trimeric units with the composition [(NaL)3.3H2O]. Each sodium has a distorted octahedral oxygen coordination. In [LReOBr2] the ReO4Br2 octahedron is only slightly distorted.