Very short F-H center dot center dot center dot F hydrogen bond in L-argininium fluoride hydrogen fluoride

There are two symmetry-independent formula units of the title compound, C6H 15N4O2+. F-. HF, per cell. Both cations have a zwitterionic form, protonate d at both the guanidyl and amino groups. The two symmetry-independent catio ns differ in their conformation. In one of them the C-gamma atom is in a ga uche position to both the amino and carboxyl groups, while in the other thi s atom is trans to the amino group. The two anions have very similar geomet ry. The F- ions are strongly hydrogen bonded to an HF molecule [F-H ... F 2 .233 (2) and 2.248(3)Angstrom], thereby forming an asymmetric non-linear bi fluoride anion. These F ... F distances are the shortest reported for an as ymmetric HF2- anion.