Phenoxo-Bridged Dimeric Structure of Technetium (I) Tricarbonyl Complex with Schiff Base Ligand

Abstract

Technetium (I) carbonyl complexes such as [Tc (CO) 3 (salbut) ]2 (salbut=2- (1-butylnitrilomethylidyne) phenolato), Tc (CO) 3 (salbut) (CH3CN) and Tc (CO) 3 (salbut) (py) (py=pridine) with Schiff base ligands were synthesized. The dinuclear complex [Tc (CO) 3 (salbut) ]2 is the first phenoxo-bridged dinuclear technetium complex. From X-ray crystallography, this dinuclear complex was revealed to be a “dimer” composed of two Tc (CO) 3 (salbut) subunits bridged by two oxygen atoms of the salbut ligand. The two Tc (CO) 3 (salbut) subunits are in inversion symmetry each other. Schiff base Hsalbut loses a phenol proton through the ligand exchange reaction and coordinates to the technetium atom as a bidentate ligand with nitrogen and oxygen atoms. Three carbonyl ligands coordinate to the technetium atom in a facial configuration. Structures of [Tc (CO) 3 (salbut) ]2 in solvents were investigated by NMR and UV-vis spectroscopy. The mononuclear complex Tc (CO) 3 (salbut) (solv) (solv=solvent molecule) was formed in strong Lewis base solvents like acetonitrile and pyridine. In weak Lewis base solvents like dichloromethane and benzene, on the other hand, the dinuclear [Tc (CO) 3 (salbut) ]2 complex was stable.