Chromium-Thiolate Complex Undergoing C-S Bond Cleavage.

The cleavage of C-S bonds represents a crucial step in fossil fuel refinement to remove organosulfur impurities. Efforts are required to identify alternatives that can replace the energy-intensive hydrodesulfurization process currently in use. In this context, we have developed a series of bis-thiolato-ligated Cr III complexes supported by the L 2- ligand (L 2- = 2,2'-bipyridine-6,6'-diyl(bis(1,1-diphenylethanethiolate), one of them displaying desulfurization of one thiolate of the ligand under reducing and acidic conditions at ambient temperature and atmospheric pressure. While only 5-coordinated complexes were previously isolated by reaction of L 2- with 3d metal M III ions, both 5- and 6-coordinated mononuclear complexes have been obtained in the case of Cr III , viz., [Cr III LCl], [Cr III LCl 2 ] - , and [Cr III LCl(CH 3 CN)]. The investigation of the reactivity of [Cr III LCl(CH 3 CN)] under reducing conditions led to a dinuclear [Cr III 2 L 2 (μ-Cl)(μ-OH)] compound and, in the presence of protons, to the mononuclear Cr III complex [Cr III (L N2S ) 2 ] + , where L N2S- is the partially desulfurized form of L 2- . A desulfurization mechanism has been proposed involving the release of H 2 S, as evidenced experimentally.