Coordination Structure of Samarium Diiodide in a Tetrahydrofuran–Water Mixture

Authors

Yamamoto, Akira; Liu, Xueshi; Arashiba, Kazuya; Konomi, Asuka; Tanaka, Hiromasa; Yoshizawa, Kazunari; Nishibayashi, Yoshiaki; Yoshida, Hisao

Abstract
Chemoselective reductive conversion of organic and inorganic compounds has been developed by the combination of samarium(II) diiodide (SmI₂) and water. Despite the extensive previous studies to elucidate the role of water in the reactivity of SmI₂, the direct structural data of the reactive Sm²⁺–water complexes, SmI₂(H₂O)_n, in an organic solvent–water mixture have not been reported experimentally so far. Herein, we performed the structure analysis of the Sm²⁺–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 Sm²⁺–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 SmI₂/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 Sm²⁺–water complex system.

Inorganic Chemistry: https://pubs.acs.org/doi/full/10.1021/acs.inorgchem.2c03752