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

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Abstract
The alpha,alpha'-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) Angstrom) across the central dimeric ring and "interdimer" Na-C connections (2.8718(15) Angstrom). Dissolution of complexes 3-6 and their lithiated derivatives [PhSO2CHCNLi.TMEDA], 1, and [t-BL)SO2CHCNLi.THF], 2, in DMSO-d(6) results in almost identical chemical shifts for each type of ligand. This suggests that charge-separated complexes of the form [RSO2CHCN](-)[M(DMSO-d(6))(n)](+) are formed in highly polar solution.

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