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 = (η5-(C5H4)2Fe]

Abstract

The neutral diethyl 4,4′-(ferrocene-1,1′-diyl)dibenzoate, Fe[η5-(C5H4)(4-C6H4CO2Et)]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{η5-(C5H4)-4-C6H4CO_2^-}2]·0.6H2O with Z′ = 5. Compound (I) crystallizes in the triclinic system, space group P\bar 1, 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{η5-(C5H4)-4-C6H4CO_2^-}2]5·3H2O. The five independent 1,1′-Fc[(4-C6H4CO2)−]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 = η5-(C5H4)2Fe]. The five dianions differ in the cisoid orientations of their pendant benzoate groups, with four having their —C6H4— groups mutually oriented at interplanar angles from 0.6 (3) to 3.2 (3)° (as π...π stacked C6 rings) and interacting principally with Na+ ions. The fifth dianion is distorted and opens up to an unprecedented —C6H4— interplanar angle of 18.6 (3)° through bending of the two 4-C6H4CO2 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(C6H4)2 groups are arranged perpendicular to the layers and mutually interlock through a series of efficient C—H...π stacking contacts in a herringbone fashion to produce an overall segregation of polar and non-polar entities.