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Mechanochemically Driven Transformations in Organotin Chemistry: Stereochemical Rearrangement, Redox Behavior, and Dispersion-Stabilized Complexes

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posted on 2018-10-26, 00:00 authored by Ross F. Koby, Timothy P. Hanusa, Nathan D. Schley
Ball milling a mixture of the bulky allyl K­[A′] {[A′] = [1,3-(SiMe3)2C3H3]} and SnCl2 in a 2:1 ratio for 5 min leads to the tris­(allyl) stannate [SnA′3K], which forms a coordination polymer in the solid state. Longer grinding of the 2:1 mixture (15 min), or the use of a 3:1 ratio of reagents, initiates a disproportionation reaction and the chiral tetra­(allyl)­tin species [SnA′4] is produced. A small amount of a diastereomeric [SnA′4] complex with meso symmetry can also be isolated with extended grinding. These products have been structurally authenticated with single-crystal X-ray crystallography. The tetra­(allyl) species [SnA′4] are sterically crowded and decompose relatively quickly (<1 h) in hydrocarbon solvents. In the solid state, they are much more persistent (several months) and evidently owe their stability to internal London dispersion interactions, as evidenced by multiple close H···H′ interligand contacts. Dispersion-corrected DFT calculations have been used to confirm the critical contribution of dispersion interactions to their stability. None of these products are available in their isolated forms from solution-based reactions, demonstrating the ability of mechanochemical activation to access otherwise unobtainable transformations in organotin chemistry.