Aggregation Patterns in α,α‘-Stabilized Carbanions: Assembly of a Sodium Cage Polymer by Slip-Stacking of Dimers

The α,α‘-stabilized carbanion complexes [PhSO2CHCNNa·THF], 3, [t-BuSO2CHCNNa], 4, [PhSO2CHCNK], 5, [t-BuSO2CHCNK], 6, and [MeSO2CHCNLi·TMEDA], 7, have been synthesized via the metalation of the parent (organo)sulfonylacetonitriles by BuLi, BuNa, or BnK in THF solution (or THF/TMEDA in the case of 7). In addition, complexes 3 and 7 have been characterized by single-crystal X-ray analyses and have been found to adopt related structures in the solid state. Complex 7 is a molecular dimer containing a central 12-membered (OSCCNLi)2 ring core, with each metal rendered tetracoordinate by binding to a chelating TMEDA molecule. As found in related complexes, no direct carbanion to lithium contacts are present in the structure of 7. Complex 3 forms a polymeric cage structure composed of associated “dimeric” (OSCCNNa)2 rings, similar to those found in 7. The larger sodium cations, and the presence of only one THF molecule/metal, allow additional contacts with the anions, leading to hexacoordination at the metal centers. These contacts include long-range transannular Na−N interactions (2.8042(14) Å) across the central dimeric ring and “interdimer” Na−C connections (2.8718(15) Å). Dissolution of complexes 3−6 and their lithiated derivatives [PhSO2CHCNLi·TMEDA], 1, and [t-BuSO2CHCNLi·THF], 2, in DMSO-d6 results in almost identical chemical shifts for each type of ligand. This suggests that charge-separated complexes of the form [RSO2CHCN]-[M(DMSO-d6)n]+ are formed in highly polar solution.