Characterization and crystal structures of some fluorinated imides

Abstract

The previously known, but not well-characterized, fluorinated imides, trifluoroacetyltrifluoroacetimide, HN(C(O)CF 3) 2 ( 1), acetyltrifluoroacetimide, HN(C(O)CH 3)C(O)CF 3 ( 2), and dichlorophosphoryltrifluoroacetimide, HN(P(O)Cl 2)C(O)CF 3 ( 3), have been shown to be moderately strong acids in aqueous solution; the first two compounds have p K a’s of 2.0 and 2.1 while the last compound consumes three equivalents of base per mole of imide owing to the hydrolyzable chlorine atoms. All three imides show a window of electrochemical inactivity on platinum from 0 to near +2.0 V. On vitreous carbon, ( 1) and ( 2) are inactive from –1.0 to +1.5 V and ( 3) from –1.0 to +1.0 V (vs. SCE). ( 1) crystallizes in a body-centered tetragonal unit cell while ( 2) and ( 3) crystallize in monoclinic unit cells. Hydrogen-bonded chains are formed in ( 1) and ( 2) and hydrogen-bonded dimers are formed in ( 3). The compounds were further characterized by 1H, 19F, and 13C NMR, FTIR, and elemental analysis.