Coordination Structure of Samarium Diiodide in a Tetrahydrofuran-Water Mixture.

Chemoselective reductive conversion of organic and inorganic compounds has been developed by the combination of samarium(II) diiodide (SmI 2 ) and water. Despite the extensive previous studies to elucidate the role of water in the reactivity of SmI 2 , the direct structural data of the reactive Sm 2+ -water complexes, SmI 2 (H 2 O) n , in an organic solvent-water mixture have not been reported experimentally so far. Herein, we performed the structure analysis of the Sm 2+ -water complex in tetrahydrofuran (THF) in the presence of water by in situ X-ray absorption spectroscopy using high-energy X-rays (Sm K-edge, 46.8 keV). The analysis revealed the dissociation of the Sm 2+ -I bonds in the presence of ≥ eight equivalents of water in the THF-water mixture. The origin of the peak shift in the UV/visible absorption spectra after the addition of water into SmI 2 /THF solution was proposed based on electron transitions simulated with time-dependent density-functional-theory calculations using optimized structures in THF or water. The obtained structural information provides the fundamental insights for elucidating the reactivity and chemoselectivity in the Sm 2+ -water complex system.