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=F, 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.