Reaction of the CH-acidic compounds 2-nitropropane, cyclopentadiene and 9-ethylfluorene with HON (nBu)4 affords the corresponding tetrabutylammonium salts in crystalline form, which have been characterized by X -ray structure analysis. The nitrostabilized salt is not a “naked ” anion (real carbanion). Rather, the α-methylene entities of the N+(nBu)4 cations form relatively strong hydrogen bonds with the O -atom s of the nitronateanion, forming dimers in a three-dimensional network. In solution dimers in the form of supramolecular ion pairs exist. In contrast, the cyclopentadienyl anion appears to be a real carbanion, since anion and cation do not interact with one another via H -bonding. The structure of the N+(nBu)4 salt of the 9-ethylfluorenyl anion is a special case in that closer contacts between cation and anion occur, which may be indicative of unusual [CH ··· C]- bonding. All three salts function as initiators in the metal-free anionic polymerization of acrylates and methacrylates at room temperature. In the case of tetrabutylammoniumcyclopentadienide, star polymers are formed.
The Mechanism of the Propagation in the Anionic Polymerization of Polystyryllithium in Non-Polar Solvents Elucidated by Density Functional Theory Calculations. A Study of the Negligible Part Played by Dimeric Ion-Pairs under Usual Polymerization Conditions