Synthesis and characterization of homoleptic chromium(III) complexes containing pyridine-2-thionato ligands and of the co-crystal (1:1) bis(pyridine-2-thionato)(pyridine-2-dithionato) chromium(III) tris(pyridine-2-thionato) chromium(III)

Abstract

The reaction of [Cr(CO)6] with a series of heterocyclic bidentate (N,S) ligands in refluxing mesitylene afforded the homoleptic trischelate complexes [Cr(3-Me3SipyS)3] (2), [Cr(3-CF3pyS)3] (3) and [Cr(5-CF3pyS)3] (4), where R-pyS stands for the anion of the corresponding substituted pyridine-2-thione ligand. Studies in the solid state by X-ray diffraction showed that the reaction with the unsubstituted ligand HpyS yielded the compound [Cr(pyS)3]/[Cr(pyS)2(pySS)] (1), which is a two-component co-crystal comprising the homoleptic species [Cr(pyS)3] (1a) and the heteroleptic species [Cr(pyS)2(pySS)] (1b), in a 1:1 ratio. While the structure of the species [Cr(pyS)3] (1a) is analogous to that of other homoleptic compounds, [Cr(RpyS)3], the species [Cr(pyS)2(pySS)] (1b) is an unusual heteroleptic complex containing both pyridine-2-thionate and pyridine-2-dithionate ligands. All of the compounds obtained were characterized by microanalysis and FAB spectrometry, and by IR and UV–Vis spectroscopies. X-ray studies showed that in all cases the metal is in a distorted octahedral environment with the heterocyclic ligand acting as a bidentate (N,S) chelate system. The supramolecular organization in complexes (1) and (2) through hydrogen bonding, weak C–H⋯π and π–π interactions was analyzed.