Unusual synthesis and x-ray structure of cis-dichloro[1,2-bis(o-(diphenylphosphino)phenyl)ethane-1,2-diolato(2-)]technetium(IV) hemiethanol solvate

Technetium phosphine complexes are stable and thus are useful in the design of 99mTc radiopharmaceuticals.1,2 In this context the most important properties of phosphine ligands are their ability to reduce the pertechnetate(VII) ion and their ability to stabilize low oxidation states by means of pi-back-bonding.Technetium-99m phosphine complexes have been investigated for biological purposes,1,7,8 and a few are very close to being used as radiopharmaceuticals. Chelating ligands containing both phosphorus(III) and other coordinating atoms offer new possibilities in the development of this field. The ligand o-(diphenylphosphino)benzaldehyde (Ph2C6H4CHO) is one of the simplest possibile bidentate O,P-chelating phosphine ligands. We have studied the reaction of this ligand with oxotetrachlorotechnetate(V) and observed an unexpected Tc(IV) product containing an O2P2-tetradentate ligand. The synthesis and X-ray structural characterization of this unusual product are now reported.