Solvent-free hydrosilylation of carbonyl compounds catalyzed by organotin(IV) compounds

Four new organotin(IV) compounds, [R₂Sn(L)] [R = Ph (1), Me (2), n-Bu (3), and t-Bu (4)], have been synthesized from a polydentate pro-ligand (E)-2,4-dichloro-6-(((2-hydroxy-5-methylphenyl)imino)methyl)phenol (H2L). Organotin(IV) halides such as Ph₂SnCl₂, Me₂SnCl₂, (n-Bu)₂SnCl₂, and (t-Bu)₂SnCl₂ were reacted with the pro-ligand using Et₃N as a base to form compounds 1-4. FT-IR spectroscopy, ¹H, ¹³C{¹H}, ¹¹⁹Sn{¹H} NMR spectroscopy, HR-MS, and single-crystal X-ray diffraction studies were used to characterize all these newly synthesized compounds. The Gutmann-Beckett method was employed to assess the Lewis acidity of all Sn(IV) compounds. All Sn(IV) compounds were tested for their catalytic efficiency in the solvent-free hydrosilylation reaction of various carbonyl compounds. The maximum yield of the silyl ethers was found to be 95%. A plausible mechanism is described based on the experimental evidence and theoretical calculations. The present study provides the first report on the use of air-stable and moisture-stable Lewis acidic organotin(IV) compounds for the hydrosilylation of carbonyl compounds.