Nitrido- and oxo-technetium(V) chelate complexes with N2S2 ligands: synthesis and crystal structures

Abstract

Diaminedithiol ligands (N₂S₂) of the type HSCR₂CH₂NR′CH₂CH₂NR′CH₂CR₂SH, where R = Me or Et and R′= Me or Et (H₂L) or H (H₄L), react with [TcNCl₂(PPh₃)₂] and [AsPh₄][TcOCl₄] forming neutral or cationic complexes of technetium(V) containing the [TcN]²⁺ and [TcO]³⁺ moieties, respectively. They are stable in the range pH 2–12.5; at pH 12.5 the oxo-complexes with H₄L become neutral due to deprotonation of one of two NH groups. The complexes have been characterized by elemental analysis, IR and ¹H NMR spectra, magnetic susceptibility and conductivity measurements. The structures of [TcO(L¹)][BPh₄](R = Me, R′= Et) and [TcO(H₂L³)]Cl (R = Et, R′= H) have been determined by single-crystal X-ray analysis. The co-ordination around Tc^V is distorted square-pyramidal in each case where the Tc atom is displaced from the plane defined by N(1), N(2), S(1), S(2) towards the O atom by 0.774(1) and 0.7731 (3)Å, respectively.