Tin—Tin π Bonding as a Conduit for Alkali‐Metal Reduction

Reactions of the doubly reduced distannynes, Ar'SnSnAr'M2, (Ar' = C6H3-2,6-Dipp; M = Li, Na, K), with the successively heavier group 1 elements (M') result in reduction of M and the isolation of Ar'SnSnAr'M'2. Although the viability of these observations, along with the reversible formation of Ar'SnSnAr'K2 by treatment of Ar'SnSnAr'Rb2 with potassium, is successfully predicted by a combined theoretical and thermochemical analysis, assessment of the bonding within Ar'SnSnAr'M2 suggests that any M+ ns valence orbital contribution should be too high in energy to effect M+ reduction. Based on a consideration of the Sn─Sn π bonding and theoretical assessment of the resultant frontier orbitals, however, we suggest that the electron transfer necessary for M+ reduction, occurs intramolecularly and via a suitably disposed π* SOMO of the putative radical anions, Ar'SnSnAr'M2•-.