| Abstract: | Structures of Sterically Overcrowded or Charge Perturbed Molecules. 9. Tetracyanoethylene Potassium Dimethoxyethane The single crystal structure of (NC)2C?C(CN)2 ?K⊕(H3CO? CH2CH2? OCH3)] reveals 4 formula units per monoclinic (P21/n) unit cell. The tetracyanoethylene radical anions are stapled within slightly undulated layers exhibiting alternating average intermolecular distances of 315 pm and 360 pm between their central C?C bonds. In- between the closer layers both are interspersed the eight-fold coordinated K⊕ counter cations and the solvating dimethoxyethane molecules with contact distances K⊕…?N of 282 to 306 pm and K⊕…?O of 279 to 294 pm. The molecular halves of the radical anions (NC)2C?C(CN)2? are twisted by 12° and the C?C, C? C and C?N bond length amount to 142, 142, and 114 pm, respectively. These structural features are discussed by comparison with those of analogous cyanohydrocarbon salts, with those of the neutral molecule, its largely interaction-free anion and its dianion as well as with results of geometry-optimized MNDO calculations. |
