Synthesis and X-ray structure of a novel technetium(IV) complex with tris(hydroxymethyl)(trimethylammonio)methane iodide as a ligand

Until recently, the only known complexes of Tc(IV) with organic chelating ligands were dimers built around the characteristic '[Tc(μ-O)2Tc]' core. As reported 5 years ago, mononuclear complexes have also been synthesized where the Tc(IV) center is coordinated to the oxygen atoms of an alcohol. A promising group of other tridentate chelating alcoholato ligands are the derivatives of tris(hydroxymethyl)methane, with a 'tripod' structure. It has been reported that these alcohols, schematically shown in Figure 1, form stable complexes with metal centers of A type, e.g. Fe(III);5 thus the formation of Tc(IV) complexes could be expected. The authors, therefore, decided to investigate the 'tripod' coordination chemistry of technetium and here report the synthesis and the X-ray structure of a stable mononuclear 1:2 Tc(IV) complex with a derivative of tris(hydroxymethyl)methane with R = N(CH3)3+, i.e. the cation (H3THMT)+ that gives the complex [Tc(THMT)2]