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 CrIII complexes supported by the L2- ligand (L2- = 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 L2- with 3d metal MIII ions, both 5- and 6-coordinated mononuclear complexes have been obtained in the case of CrIII , viz., [CrIII LCl], [CrIII LCl2 ]- , and [CrIII LCl(CH3 CN)]. The investigation of the reactivity of [CrIII LCl(CH3 CN)] under reducing conditions led to a dinuclear [CrIII 2 L2 (μ-Cl)(μ-OH)] compound and, in the presence of protons, to the mononuclear CrIII complex [CrIII (LN2S )2 ]+ , where LN2S- is the partially desulfurized form of L2- . A desulfurization mechanism has been proposed involving the release of H2 S, as evidenced experimentally.