Ionic Liquids Containing the Triply Negatively Charged Tricyanomelaminate Anion and a B(C6F5)3 Adduct Anion

Room-temperature ionic liq- uids containing the triply charged tri- cyanomelaminate (tcmel) ion (C3N6(CN)3) 3� were synthesized. The 1- methyl-3-methylimidazolium (MMIm), 1-ethyl-3-methylimidazolium (EMIm), and 1-butyl-3-methylimidazolium (BMIm) salts of the tricyanomelami- nate ion have glass transition tempera- tures (� 6, � 20, and � 308C) similar to those found for the analogous mono- meric dicyanoamide salts. They are thermally stable up to over 2008C and dissolve in polar organic solvents. Ad- dition of BA6F5)3 to M3A (M = Na, MMIm, EMIm, BMIm) yields salts containing the very voluminous adduct ion (C3N6A·BA6F5)3}3) 3� (tcmel_3B). The solid-state structure of (MMIm)3- A shows only long cation···anion contacts but in large number, while the solid-state structure of (NaA3)3- A·1.76 THF displays strong in- teractions of the sodium cation with the amido nitrogen atoms of the anion. Hence this adduct anion cannot be re- garded as a weakly coordinating anion. A similar situation is found for the MMIm salt, (MMIm)3A· 2.66 CH2Cl2, in which weak hydrogen bonds with the acidic proton of the MMIm ion are observed. On the basis of computations the energetics, struc- tural trends, and charge transfer of adduct anion formation were studied.