Element-Ligand Cooperativity of Hypervalent Organotin(IV) Compounds in Hydroboration Reaction of Carbonyl Compounds

Four air- and moisture-stable hypervalent organotin compounds [R₂Sn(L)], where R = Ph (1), t-Bu (2), n-Bu (3), and Me (4), supported by polydentate pro-ligand (H₂L), have been designed and developed. The compounds are characterized using FT-IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy, HRMS, and single-crystal X-ray diffraction studies. The Gutmann-Beckett method assessed the Lewis acidity of all the compounds (1-4). All compounds (predominantly 1) showed prominent catalytic activities toward the hydroboration reaction. A variety of desired products are obtained with good to excellent yields. Exemplary catalytic activity, a significant turnover number, a wide substrate range, and mild reaction conditions have made these compounds suitable catalysts for the hydroboration reaction. Moreover, the Lewis acidic and basic sites of the compounds play an active role in the catalytic process, thus making them "bifunctional catalysts". A plausible mechanism is proposed for the catalytic process, supported by spectroscopic evidence and computational studies.