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)

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-Me(3)SipyS)(3)] (2), [Cr(3-CF(3)pyS)(3)] (3) and [Cr(5-CF(3)pyS)(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 center dot center dot center dot pi and pi-pi interactions was analyzed. (c) 2013 Elsevier Ltd. All rights reserved.