Synthesis and characterization of technetium(V) and rhenium(V) oxo-complexes with Schiff-base ligands containing the ONN donor-atom set. Molecular structure of trans-dichloro-oxo[1-(8′-quinolyliminomethyl)-2-naphtholato-NN′O]technetium(V)

Abstract

Six-co-ordinate complexes of technetium(V) and rhenium(V) containing the MO³⁺(M = Tc or Re) core were synthesized from [MOCl₄]^–via ligand-exchange reactions using tridentate Schiff-base ligands containing the ONN donor-atom set. The complexes of general formula [MOCl₂Lⁿ][n= 1 – 4; L¹= 1-(8′-quinolyliminomethyl)-2-naphtholate, L²=N-(8′-quinolyl)salicylideneiminate, L³= 3-methoxy-N-(8′-quinolyl)salicylideneiminate, L⁴=N-(2′-dimethylaminoethyl)salicylideneiminate] were characterized by means of physico-chemical measurements and [TcOCl₂L¹] also by X-ray diffraction analysis. The technetium co-ordination environment in the last complex is a distorted octahedron with the N₂O ligand-atom set and the oxo-oxygen occupying the equatorial plane and the two chlorine atoms, respectively trans, in axial positions. The complex crystallizes in monoclinic space group P2₁/a with a= 23.262(8), b= 7.301(4), c= 11.444(5)Å, β= 98.98(5)°, and Z= 4. The structure has been refined to R= 0.048 for 2 693 observed reflections.