Piperidinium N-(ferrocenylcarbonyl)glycinate

The title compound, (C5H12N)[Fe(C5H5)(C8H7NO3)], resulting from neutralization of N-(ferrocenylcarbonyl)glycine with piperidine, is built up from discrete ions that assemble into sheets via the combination of conventional and weak hydrogen bonds. The key repeating unit is constituted by two piperidium cations and two carboxylate anions that assemble into a centrosymmetric array via conventional and bifurcated N—H⋯O hydrogen bonds. The aggregates thus formed are further interlinked by N—H⋯O interactions and supportive C—H⋯O contacts into layers oriented parallel to the bc plane.

The title compound, (C 5 H 12 N)[Fe(C 5 H 5 )(C 8 H 7 NO 3 )], resulting from neutralization of N-(ferrocenylcarbonyl)glycine with piperidine, is built up from discrete ions that assemble into sheets via the combination of conventional and weak hydrogen bonds. The key repeating unit is constituted by two piperidium cations and two carboxylate anions that assemble into a centrosymmetric array via conventional and bifurcated N-HÁ Á ÁO hydrogen bonds. The aggregates thus formed are further interlinked by N-HÁ Á ÁO interactions and supportive C-HÁ Á ÁO contacts into layers oriented parallel to the bc plane.

D-HÁ
Thus, piperidinium N-(ferrocenylcarbonyl)glycinate was obtained by acid-base reaction N-(ferrocenylcarbonyl)glycine with piperidine and isolated as a yellow, air-stable crystalline solid. Its molecular structure as determined by X-ray diffraction analysis ( Figure 1) is rather unexceptional. The geometry of the ferrocene unit is regular, showing a practically negligible variation in the Fe-C bond lengths (2.029 (19)-2.051 (2) Å). Accordingly, the distance of the iron atom to cyclopentadienyl ring centroids are quite similar (1.6429 (10) and 1.6450 (10) Å for the rings C(1-5) and C(6-10), respectively), and the dihedral angle of the least-squares cyclopentadienyl planes is only 2.28 (13) °.
The geometry of the glycinamide moiety is similar to those reported previously for methyl N- The crystal packing of the title compound is dominated by intermolecular hydrogen bonding interaction. The ions constituting the structure assemble pairwise around inversion centers by means of N-H···O hydrogen bonds from both NH protons at the piperidinium cation to adjacent carboxylate O atoms O2 and O3 as H-bond acceptors (Figure 2a; for parameters, see Table 1). An additional contact, N2-H3N···O2 has a rather unfavourable geometry and probably reflects an enforced proximity of the atoms involved. The four-membered centrosymmetric assemblies thus formed are interconnected by N-H···O hydrogen bonds between amide NH and carboxylate O3 and further by supportive C-H···O interactions ( Figure 2a, Table 1) into layers oriented parallel to the bc plane ( Figure 2b).
Yellow crystals of the title compounds were obtained by mixing equimolar amounts of piperidine and N-

Refinement
H-atoms residing on the carbon atoms were included in their calculated positions and treated as riding atoms with U iso (H) = 1.2 U eq (C). Those biding to the N and O atoms were identified on the difference electron density maps and refined as described above.