STRUCTURES OF CHARGE-PERTURBED OR STERICALLY OVERCROWDED MOLECULES .16. TETRACYANOETHYLENE SODIUM DIMETHOXYETHANE

The single crystal structure of [(NC)2C=C(CN)2-.Na+(H3CO-CH2CH2-OCH3)]infinity reveals two formula units within the triclinic (P1) unit cell. The tetracyanoethylene radical anions are arranged along parallel double layers, which are shifted relative to each other, and in between which are interspersed the sodium counter cations and their dimethoxyethane ligands. The distances within the double layers amount to 300 pm and the ones between them to 385 pm. The six-fold coordinated Na+ centers are surrounded by four radical anions with contact distances Na...N between 250 and 254 pm as well as by a twofold solvent ligand with Na...O of 238 and 241 pm. Due to the electron transfer to the acceptor molecule, its (NC)2C-halves twist by 8-degrees and the bond lengths of the N-C-C subunits, bent by each 3-degrees are shortened up to 2 pm. The structural parameters are compared to those of the analogous potassium salt [TCNE-K+DME], of the dianion [(NC)2C---C(CN)2]--, of the sodium salts [(NC)3C-Na+]infinity as well as [(NC)2C=C(CHCH)2=C(CN)2-Na+]infinity and, in addition, are discussed based on geometry-optimized MNDO calculations.