Syntheses and characterization of thallium(I) complexes with 3-nitrophenoxide [Tl(3-np)], 4-nitrobenzoate [Tl(4-nb)] and 2,4-dinitrophenoxide [Tl(2,4-dnp)]: X-ray crystal structures of [Tl(3-np)]n and Tl(2,4-dnp) (two new polymeric compounds)

Complexes thallium(I)3-nitrophenoxide [Tl(3-np)], thallium(I)2,4-dinitrophenoxide [Tl(2,4-dnp)] and thallium(I)4-nitrobenzoate [Tl(4-nb)] have been synthesized using a direct reaction between TlNO₃ and the appropriate ligand. The complexes have been isolated and characterized by IR spectra and CHN elemental analyses. The structures of [Tl(3-np)]_n and [Tl(2,4-dnp)] have been confirmed by X-ray crystallography. The single crystal X-ray crystallography of [Tl(3-np)]_n shows the complex to be a one-dimensional polymer as a result of bridging 3-nitrophenoxide ligands. The Tl atoms have an unsymmetrical three-coordinate, O₃ geometry (three oxygen atoms of the 3-nitrophenoxide ligand). The crystal structure of [Tl(2,4-dnp)] shows the complex to be a three-dimensional polymer as a result of bridging 2,4-dinitrophenoxide ligands. The Tl atoms have an unsymmetrical two-coordinate, O₂ geometry (two oxygen atoms of the 2,4-dinitrophenoxide ligand). The arrangement of the 3-nitrophenoxide and 2,4-dinitrophenoxide ligands suggests a gap in coordination geometry around the Tl(I) ions, occupied possibly by a stereoactive lone pair of electrons on Tl(I). There is a π–π stacking interaction between the parallel aromatic rings belonging to adjacent chains in the compounds that may help to increase the ‘gap’ in coordination geometry around the Tl(I) ions.