The synthesis and X-ray structural characterization of mer and fac isomers of the technetium(I) nitrosyl complex [TcCl2(NO)(PNPpr)]

The nitrosyl complex H[TcNOCl4] reacts with the tridentate ligand bis[(2-diphenylphosphino)propyl]amine (PNPpr) to yield a mixture of the mer or fac isomers of [TcCl2(NO)(PNPpr)]. In acetonitrile, where the ligand is freely soluble, reaction occurs at room temperature to yield mostly the mer isomer with the linear nitrosyl ligand cis to the amine ligand; and the phosphine ligands arranged in a mutually trans orientation. The reaction in methanol requires reflux to dissolve the lipophilic ligand and generates the fac isomer of [TcCl2(NO)(PNPpr)] as the major product, with the tridentate ligand in a facial arrangement, leaving the chlorides and nitrosyl ligand in the remaining facial sites. The steric bulk of the tridentate ligand’s diphenylphophino-moieties results in a significant distortion from octahedral geometry, with the P–Tc–P bond angle expanded to 99.48(4)°.The infrared spectra display absorptions from these nitrosyl ligands in the 1700 and 1800 cm−1 regions for the fac and mer isomers, respectively. The ESI(+) mass spectra each display the parent ion at 647 m/z.

Graphical abstractThe nitrosyl complex [Bu4N][TcNOCl4] reacts with bis[(2-diphenylphosphino)propyl]amine (PNPpr) to give mixtures of the mer or fac isomers of [TcCl2(NO)(PNPpr)]. In acetonitrile, the mer isomer is predominantly formed. In methanol, the fac isomer of [TcCl2(NO)(PNPpr)] precipitates cleanly however both isomers form. X-ray crystal structures of each are presented.Figure optionsDownload full-size imageDownload as PowerPoint slide