Technetium(V) nitrido complexes with tetra-azamacrocycles: monocationic and neutral octahedral complexes containing the [TcN]2+ core. Crystal structure of [TcN(L1)H2O]·2H2O (H2L1= 1,4,8,11-tetra-azacyclotetradecane-5,7-dione)

Abstract

Neutral and monocationic complexes of technetium(V) containing the [TcN]²⁺ core have been synthesized by substitution reactions of [TcNCl₂(PPh₃)₂] with tetra-azamacrocycles. The ligand 1,4,8,11-tetra-azacyclotetradecane-5-one has also been prepared. The complexes have been characterized by elemental analysis, i.r. and ¹H n.m.r. spectra, conductivity, and magnetic susceptibility measurements. The complex [TcN(L¹)(H₂O)]·2H₂O (H₂L¹= 1,4,8,11-tetra-azacyclo-tetradecane-5,7-dione) has a distorted octahedral structure with a H₂O molecule in trans position to the TcN group. The quadridentate dianionic ligand forms with the Tc atom two trans five-membered and two trans six-membered metallacycles in which the Tc–N (sp²) bond distances are significantly shorter than the corresponding Tc–N (sp³) distances (2.051 vs. 2.127 Å).