Structures of bis(fluorosulfonyl)imide HN(SO2F)2, bis(trifluoromethylsulfonyl)imide HN(SO2CF3)2, and their potassium salts at 150 K

The structures of HN(SO2R)(2), R=E CF3 are formed by molecules linked by hydrogen bonds to infinite chains. While KN(SO2F)(2) is composed of alternating cations and anions, HN(SO2CF3)(2) exhibits a pronounced layer structure. In the acids, the substituents -R are in trans configuration being on the opposite sides of the plane defined by S-N-S bonds but in the salts the cis configuration with both substituents on the same side of the S-N-S plane is preferred, probably due to numerous metal-anion interactions.