Wechselwirkungen in Kristallen. 96. Darstellung und Strukturen von Salzen [RnN⊕H…︁NRn][B⊖(C6H5)4] mit Prototyp-Wasserstoffbrücken N⊕H…︁N

Interactions in Crystals. 96. Preparation and Structures of Salts R_nN^⊕H…︁NR_n]B^⊖(C₆H₅)₄] with Prototype Hydrogen Bridges N^⊕H…︁N Straightforward crystallization of ammonium salts R_nN^⊕H] X^⊖ added lithium tetraphenylborate, and amine R_nN from acetone solution yields salts R_nN^⊕H…︁NR_n]B^⊖(C₆H₅)₄] with the (under the conditions) unprotonated anions and the cations with prototype hydrogen bridges N^⊕H…︁N. The structures of both identically substituted R_nN (methylamine, trimethylamine, quinuclidine, diazabicyclooctane, and pyridine) as well as two-component cation species (quinuclidine…︁pyridine and diazabicyclooctane…︁pyridine) are reported and discussed. A Cambridge Structural Database search defines the area of charged N^⊕H…︁N interactions which can be correlated with both pK values and PM3 formation enthalpies. Additional information is provided by PM3 calculations based on the experimental structure coordinates. The charge distribution within the hydrogen bridges N^⊕H…︁N varies considerably with the individual proton donors N⁺H and proton acceptors N: Positive charges are highest at protonated quinuclidine and diazabicyclooctane centers and lowest at pyridine N acceptor centers.