SUF₄: A Terminal Monosulfido Complex of Uranium(VI) with a Linear SUF Moiety

Although there have been a few terminal sulfido complexes of uranium(VI) with either SUO or SUN moiety, it remains a question whether the terminal sulfido ligand can be stabilized in the absence of such multiply bound oxo or nitrido ligands. Herein, we report a terminal monosulfide complex of uranium(VI) in the form of SUF₄ bearing a linear SUF moiety that was prepared via the reaction of laser-ablated uranium atoms with SF₄ in cryogenic matrixes. On the basis of the results from infrared spectroscopy combined with density functional theory calculations at the B3LYP level, the SUF₄ complex possesses a trigonal bipyramid structure with singlet ground state and nonplanar C₃ symmetry where the terminal sulfido ligand is stabilized by the monovalent fluoro ligand trans to sulfur. A triple U-S bond with a positively charged sulfur atom was identified according to the natural bond orbital analysis. Inverse trans influence is present in SUF₄ as revealed by the difference in bond length between U-F_axial from the linear SUF moiety and U-F_equatorial from the UF₃ equatorial plane, which is further supported by bonding analysis.