Coordination Structure of Samarium Diiodide in a Tetrahydrofuran–Water Mixture

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.

Enabling Molecular-Level Computational Description of Redox and Proton-Coupled Electron Transfer Reactions of Samarium Diiodide

“…1%) longer than those of the X-ray structure (see Section S2.1 in the Supporting Information). A similar pattern of slight overestimation of Sm–ligand distances is seen when comparing the optimized Sm–O and Sm–I distances of SmI 2 (THF) 4 H 2 O with those obtained from in situ X-ray absorption spectroscopy on a 1:1 mixture of SmI 2 and water in THF . More generally, the PW6B95 functional, with or without empirical dispersion corrections, has been found to perform well across a broad range of transition-metal chemistry, including the prediction of spin-state stability, as well as main-group chemistry. , …”

“…A similar pattern of slight overestimation of Sm−ligand distances is seen when comparing the optimized Sm−O and Sm−I distances of SmI 2 (THF) 4 H 2 O with those obtained from in situ X-ray absorption spectroscopy on a 1:1 mixture of SmI 2 and water in THF. 16 More generally, the PW6B95 functional, with or without empirical dispersion corrections, has been found to perform well across a broad range of transition-metal chemistry, 17 including the prediction of spin-state stability, 18 as well as main-group chemistry. 19,20 The input geometries of SmI 2 (THF) 5 /SmI 2 (THF) 5 + were taken from ref 8, in which the structure of SmI 2 in THF has been explored computationally.…”

Hydroxyl-Directed Regio- and Diastereoselective Allylic Sulfone Reductions with [Sm(H2O)n]I2

“…Our group has been exploring a samarium diiodide (SmI 2 ) mediated elimination/isomerization process for asymmetric carbon atom synthesis. − We have found that upon treatment with SmI 2 and water ([Sm­(H 2 O) n ]­I 2 ), , substrates of type A are transformed into alkene products B in high yield and in some cases high diastereoselectivity (up to 90:10; Scheme ). The reaction is thought to proceed through a chelated organosamarium intermediate ( Sm–I ), formed upon the reduction and loss of the benzoyl ester (OBz).…”