(R)-N-(Ferrocenylmeth-yl)-1-hy-droxy-3-phenyl-propan-2-aminium (E)-but-2-enoate.

The crystal structure of the title salt, [Fe(C(5)H(5))(C(15)H(19)NO)](C(4)H(5)O(2)), consists of discrete ammonium and carboxyl-ate ions, which associate into infinite chains parallel to [100] by means of N-H⋯O and O-H⋯O inter-actions. These chains are further cross-linked into a three-dimensional network by additional C-H⋯O contacts and by offset π-π stacking inter-actions of inversion-related aromatic rings [centroid-centroid distance = 3.7040†(14)†à ]. The mol-ecular parameters of the ionic components are in no way unexpected, the geometry of the ammonium cation being similar to that found in other structurally characterized salts obtained from N-ferrocenylmethyl β-amino-alcohols. The (E)-but-2-enoate anion consists of two approximately planar subunits, viz the delocalized carboxyl-ate unit and the butenyl group (the latter being planar within ca. 0.002†à ), which are mutually rotated by 30.3†(4)°.