NITRIDO- AND OXO-TECHNETIUM(V) CHELATE COMPLEXES WITH N2S2 LIGANDS: SYNTHESIS AND CRYSTAL STRUCTURES

Diaminedithiol ligands (N2S2) of the type HSCR2CH2NR'CH2CH2NR'CH2CR2SH, where R = Me or Et and R' = Me or Et (H-2L) or H (H-4L), react with [TcNCl2(PPh3)2] and [AsPh4][TcOCl4] forming neutral or cationic complexes of technetium(V) containing the [Tc=N]2+ and [Tc=O]3+ moieties, respectively. They are stable in the range pH 2-12.5; at pH 12.5 the oxo-complexes with H-4L become neutral due to deprotonation of one of two NH groups. The complexes have been characterized by elemental analysis, IR and H-1 NMR spectra, magnetic susceptibility and conductivity measurements. The structures of [TcO(L1)][BPh4] (R = Me, R' = Et) and [TcO(H-2L3)]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) angstrom, respectively.