Trifluoromethanesulfonate, trifluromethylsulfonylimide, and bis(trifluoromethylsulfonyl)imide salts and ionic liquids based on 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[ 4.3.0]non-5-ene

Abstract

Trifluoromethanesulfonate, trifluoromethylsulfonylimide, and bis(trifluoromethylsulfonyl)imide salts and ionic liquids were synthesized from 2, 3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepine (1,8-diazabicyclo[5.4.0]undec-7-ene) and 2, 3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidine (1,5-diazabicyclo[4.3.0]non-5-ene). Their physicochemical properties, spectral parameters, and some chemical transformations were studied. I, II, X = H: Y = F 3 CSO 2 O (a), F 3 CSO 2 NH (b), (F 3 CSO 2 ) 2 N (c); X = Pr: Y = Cl (d), (F 3 CSO 2 ) 2 N (e); X = Ph, Y = (F 3 CSO 2 ) 2 N (f); X = F 3 CSO 2 , Y = F 3 CSO 2 O (g).First ionic liquids based on 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU,2,3,4,6,7,8,9,azepine) cations and various anions (Cl, Br, OTs, OTf) were reported previously [1-3]. Of particular interest are ionic liquids containing bis(trifluoromethylsulfonyl)imide anion (CF 3 SO 2 ) 2 N -which considerably reduces the melting point and viscosity of ionic liquids, as compared to other anions. In addition, organic salts with trifluoromethylsulfonylimide and other perfluoroalkylsulfonylimide anions are mainly hydrophobic and are characterized by high thermal and electrochemical stability [4][5][6]. First ionic liquids with trifluoromethylsulfonylimide anion were synthesized on the basis of imidazolium cation in 1995-96 [7, 8], and they subsequently found wide application [9][10][11].In the present communication we describe the synthesis of new salts and ionic liquids derived from DBU (I) and 1,5-diazabicyclo[4.3.0]non-5-ene (II, DBN, 2,3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidine) and containing trifluoromethanesulfonate, trifluoromethylsulfonylimide, and bis(trifluoromethylsulfonyl)imide anions. The initial nitrogen-containing bases, DBU and DBN, are readily obtained from ε-caprolactam and pyrrolidin-2-one, respectively, and their synthetic and commercial accessibilities are quite comparable with those of 1-alkylimidazoles that are starting compounds for the preparation of most known ionic liquids.Almost similar structures of DBU (I) and DBN (II) in salts (X = N) and ionic liquids (X = R) makes it possible to use spectral parameters of readily obtainable and identifiable salts DBUH + Y -and DBNH + Yfor identification of ionic liquids DBUR + Y -and DBNR + Y -which are synthesized by different methods.Trifluoromethanesulfonate, trifluoromethylsulfonylimide, and bis(trifluoromethylsulfonyl)imide DBU and DBN salts Ia-Ic and IIa-IIc were prepared in quantitative yield by mixing equimolar amounts of the corresponding base and trifluoromethanesulfonic acid CF 3 SO 3 H, trifluoromethanesulfonamide CF 3 S O 2 NH 2 , o r t r i f luo r o me t h a n s u l f o n i mi d e (CF 3 SO 2 ) 2 NH under solvent-free conditions or in chloroform at room temperature. The products were analyzed after removal of the solvent without additional purification. The isolated salts were colorless

Trifluoromethanesulfonamides and Related Compounds

“…In the 13 C NMR spectra a large (>10 ppm) upfield shift of the C p signal and even larger (>13 ppm) downfield shift of the C i signal is observed C n . 310 The observed changes are consistent with the change of the substituent in the phenyl ring from Tf 2 N to the DBN or DBU residue and cannot be explained for the N-triflyl salts with the [TfNPh] − as the counterion. Considering a possible mechanism of the Ph group transfer from Tf 2 NPh, we believe that it cannot proceed via the benzyne mechanism, which is realized only for extremely strong bases (like NH 2…”

“…To our surprise, the reaction successfully gave the N-phenylated triflimide salts of DBN and DBU. 310 Because in the previous studies Tf 2 NPh with N-bases gave only the products of the triflyl group transfer, 6 the structure of the products with DBN and DBU was the principal question. The comparison of the 1 H and 13 C NMR spectra of the products with those of the starting Tf 2 NPh showed strong differences.…”

“…acetonitrile, chloroform, and methylene chloride. 310 We have tried preparation of the DBN-and DBU-based ILs by the direct reaction of the corresponding bases with N-phenyltriflimide.…”

Structure and vibrational features of the protic ionic liquid 1,8-diazabicyclo[5.4.0]-undec-7-ene-8-ium bis(trifluoromethanesulfonyl)amide, [DBUH][TFSI]

“…[TFSI] [8,9,14,42] have been studied in the past by different groups. The conductivity vs. temperature dependence of [DBUH][TFSI], reported in Fig.…”

“…In the past, related [DBUH]-based PILs have been studied by other groups. Tolstikova et al prepared salts with Cl, Br, p-toluenesulfonate and triflate anions [13] and later with other fluorinated anions including [TFSI] [14], therein reporting preparation and solubility properties in diverse media, including water. The importance of the DpK a parameter in determining key chemical-physical properties of PILs has been recently highlighted: Angell et al proposed that DpK a val-ues>10 lead to substantial proton transfer and hence highly ionized PILs [6].…”