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

Ball milling a mixture of the bulky allyl K[A'] {[A'] = [1,3-(SiMe3)(2)C3H3](-)} and SnCl2 in a 2:1 ratio for 5 min leads to the tris(allyl)stannate [SnA'K-3](infinity), 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 center dot center dot center dot 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.