Synthesis of six-co-ordinate technetium(V) complexes with N-phenylsalicylideneimine. X-Ray crystal structure of chloro-oxobis(N-phenylsalicylideneiminato)technetium(V)

Abstract

The complexes [TcOClL¹₂](1) and [AsPh₄][TcOCl₃L¹](2)(HL¹=N-phenylsalicylideneimine) of the long-lived isotope technetium-99 were synthesized starting from [AsPh₄][TcOCl₄]. The characterization was performed by elemental analysis of technetium and chlorine and i.r. spectra. The crystal structure of (1) has been determined and refined from 1 259 diffractometer data (up to 2θ= 44°) to a final R of 0.057. Crystals are monoclinic, space group P2₁/n, with unit-cell dimensions a= 12.854(4), b= 15.840(7), c= 11.433(4) A, β= 93.43(2)°, and Z= 4. The co-ordination around Tc is approximately octahedral with the two chelate ligands mutually orthogonal, one ligand bridging an equatorial and an apical position and the other two, equatorial ones. The equatorial plane is completed by the Cl atom and the other apical position is occupied by the O atom strongly bonded to Tc [Tc–O 1.67(1)Å]. The simple method of synthesis, the short reaction time, and the versatility of this type of Schiff base ligand is of importance in the design of technetium-99m labelled radiopharmaceuticals containing N and O co-ordinating centres.