The reaction of 1 equiv of the dimeric lithium salt of a new London dispersion effect donor ligand {Li(CH-2,4,6-Cy)·OEt} (Cy = cyclohexyl) with SnCl afforded the distannene {Sn(CH-2,4,6-Cy)} (). The distannene remains dimeric in solution, as indicated by its room-temperature Sn NMR signal (δ = 361.3 ppm) and its electronic spectrum, which is invariant over the temperature range of -10 to 100 °C. The formation of the distannene, which has a short Sn-Sn distance of 2.7005(7) Å and greatly enhanced stability in solution compared to that of other distannenes, is due to increased interligand London dispersion (LD) attraction arising from multiple close approaches of ligand C-H moieties across the Sn-Sn bond. DFT-D4 calculations revealed a dispersion stabilization of dimer of 38 kcal mol and a dimerization free energy of Δ = -6 kcal mol. In contrast, the reaction of 2 equiv of the similarly shaped but less bulky, less hydrogen-rich Li(CH-2,4,6-Ph)·(OEt) with SnCl yielded the monomeric stannylene Sn(CH-2,4,6-Ph) (), which is unstable in solution at ambient temperature.
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http://dx.doi.org/10.1021/jacs.1c09976 | DOI Listing |
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