Hyperconjugation Controls One-Bond Carbon-Tin Coupling Constants in Anomeric Tin Compounds: A Theoretical Study.
Journal Article
Overview
abstract
One-bond 119Sn-13C couplings in organostannanes are sensitive to local stereoelectronic effects, yet quantitative rules linking hyperconjugation to 1J(Sn-C) remain limited, especially at anomeric centers. We combine DFT studies with NBO analysis across 77 cyclic scaffolds, including matched axial/equatorial (α/β) anomeric pairs, to relate antiperiplanar donor → σ*(C-Sn) delocalization to 1J(Sn-C). Validation against 1J(C-H) benchmarks reproduces Perlin-type axial/equatorial differences and the classical reversal in 1,3-dithianes. 1J(Sn-C) scales with the magnitude of donation. Pairwise comparisons are equally diagnostic: across 27 α/β (axial/equatorial) pairs, equatorial isomers show larger couplings in 92% of cases, and ΔJ correlates with Δdonation, rationalizing the β > α hierarchy. Ring-size controls reveal a geometric signature consistent with known ring size relationships with coupling constants: as the size of the ring increases, 1J(C-H) decreases. Incorporation of sulfur in the ring can cause the β > α 1J(Sn-C) behavior observed in most other cyclic scaffolds to invert with axial 1J(Sn-C) being greater than equatorial 1J(Sn-C). A single-parameter empirical scaling (J(corr) = -1.419·J(calc)) improves absolute agreement with experiment without perturbing trends and brings negative calculated 1J(Sn-C) to the experimentally derived positive 1J(Sn-C). Collectively, these results deliver a practical, mechanistic framework for predicting tin-carbon coupling constants and assigning the anomeric configuration in anomeric organotin compounds.
