Mechanistic elucidation of monoalkyltin(iv)-catalyzed esterification.

Authors :: Wolzak LA
Hermans JJ
de Vries F
van den Berg KJ
Reek JNH
Tromp M
Korstanje TJ
Source :: Catalysis science & technology [Catal Sci Technol] 2021 Feb 17; Vol. 11 (10), pp. 3326-3332. Date of Electronic Publication: 2021 Feb 17.
Publication Year :: 2021
Abstract: Monoalkyltin(iv) complexes are well-known catalysts for esterification reactions and polyester formation, yet the mode of operation of these Lewis acidic complexes is still unknown. Here, we report on mechanistic studies of n -butylstannoic acid in stoichiometric and catalytic reactions, analyzed by NMR, IR and MS techniques. While the chemistry of n -butyltin(iv) carboxylates is dominated by formation of multinuclear tin assemblies, we found that under catalytically relevant conditions only monomeric n -BuSn(OAc) <subscript>3</subscript> and dimeric ( n -BuSnOAc <subscript>2</subscript> OEt) <subscript>2</subscript> are present. Density functional theory (DFT) calculations provide support for a mononuclear mechanism, where n -BuSn(OAc) <subscript>3</subscript> and dimeric ( n -BuSnOAc <subscript>2</subscript> OEt) <subscript>2</subscript> are regarded as off-cycle species, and suggest that carbon-oxygen bond breaking is the rate-determining step.<br />Competing Interests: The authors declare no conflict of interest.<br /> (This journal is © The Royal Society of Chemistry.)