R. Vianello, Z. Maksić
Aug 1, 2005
Citations
0
Influential Citations
40
Citations
Journal
European Journal of Organic Chemistry
Abstract
The acidity of the parent 1H-benz[f]indene (1a), 1H-benz[e]indene (2a), 1H-benz[fg]acenaphthylene (3a) and 1H-cyclopenta[l]phenanthrene (4a) and of their polycyano derivatives is examined in the gas phase and in DMSO by the DFT-B3LYP methods. It is shown that the parent hydrocarbons exhibit modest acidities, whereas a dramatic increase in acidity is observed upon multiple cyanation leading to hyperstrong neutral organic superacids. It is found that polycyano derivatives undergo prototropic tautomerism with a consequence that the most stable tautomer contains a ketene imine C=C=NH functionality. The origin of their highly pronounced acidity is identified as a very strong anionic resonance effect efficiently assisted by a large number of CN groups in a concerted manner. It is stressed that the polycyanated anions are very stable and have a highly dispersed negative charge, which should lead to a low nucleophilicity and weak coordinating properties, thus making them potentially very useful in academic research and technological applications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)