Supramolecular assemblies in the crystals of carboxylate salts prepared from a ferrocene β-aminoalcohol

(R)-N-(Ferrocenylmethyl)-1-hydroxy-3-phenylpropan-2-aminium (E)-but-2-enoate

The crystal structure of the title salt, [Fe(C₅H₅)(C₁₅H₁₉NO)](C₄H₅O₂), consists of discrete ammonium and carboxyl­ate ions, which associate into infinite chains parallel to [100] by means of N—H⋯O and O—H⋯O inter­actions. These chains are further cross-linked into a three-dimensional network by additional C—H⋯O contacts and by offset π–π stacking inter­actions of inversion-related aromatic rings [centroid–centroid distance = 3.7040 (14) Å]. The mol­ecular 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-amino­alcohols. The (E)-but-2-enoate anion consists of two approximately planar subunits, viz the delocalized carboxyl­ate unit and the butenyl group (the latter being planar within ca. 0.002 Å), which are mutually rotated by 30.3 (4)°.

1,1'-Fc(4-C6H4CO2Et)2 and its unusual salt derivative with Z' = 5, catena-[Na+]2[1,1'-Fc(4-C6H4CO2-)2].0.6H2O [1,1'-Fc = (eta5-(C5H4)2Fe]

The neutral diethyl 4,4'-(ferrocene-1,1'-diyl)dibenzoate, Fe[eta(5)-(C(5)H(4))(4-C(6)H(4)CO(2)Et)](2) (I), yields (II) (following base hydrolysis) as the unusual complex salt poly[disodium bis[diethyl 4,4'-(ferrocene-1,1'-diyl)dibenzoate] 0.6-hydrate] or [Na(+)](2)[Fe{eta(5)-(C(5)H(4))-4-C(6)H(4)CO(2)(-)}(2)].0.6H(2)O with Z' = 5. Compound (I) crystallizes in the triclinic system, space group P1, with two molecules having similar geometry in the asymmetric unit (Z' = 2). The salt complex (II) crystallizes in the orthorhombic system, space group Pbca, with the asymmetric unit comprising poly[decasodium pentakis[diethyl 4,4'-(ferrocene-1,1'-diyl)dibenzoate] trihydrate] or [Na(+)](10)[Fe{eta(5)-(C(5)H(4))-4-C(6)H(4)CO(2)(-)}(2)](5).3H(2)O. The five independent 1,1'-Fc[(4-C(6)H(4)CO(2))(-)](2) dianions stack in an offset ladder (stepped) arrangement with the ten benzoates mutually oriented cisoid towards and bonded to a central layer comprising the ten Na(+) ions and three water molecules [1,1'-Fc = eta(5)-(C(5)H(4))(2)Fe]. The five dianions differ in the cisoid orientations of their pendant benzoate groups, with four having their -C(6)H(4)- groups mutually oriented at interplanar angles from 0.6 (3) to 3.2 (3) degrees (as pi...pi stacked C(6) rings) and interacting principally with Na(+) ions. The fifth dianion is distorted and opens up to an unprecedented -C(6)H(4)- interplanar angle of 18.6 (3) degrees through bending of the two 4-C(6)H(4)CO(2) groups and with several ionic interactions involving the three water molecules (arranged as one-dimensional zigzag chains in the lattice). Overall packing comprises two-dimensional layers of Na(+) cations coordinated mainly by the carboxylate O atoms, and one-dimensional water chains. The non-polar Fc(C(6)H(4))(2) groups are arranged perpendicular to the layers and mutually interlock through a series of efficient C-H...pi stacking contacts in a herringbone fashion to produce an overall segregation of polar and non-polar entities.