title: The effect of counter-ions on the supramolecular arrangement of (benzonitrile)[1,2-bis(diphenylphosphino)ethane](eta5-cyclopentadienyl)iron(II) cations.
abstract: The title compound, [1,2-bis(diphenylphosphino)ethane](eta5-cyclopentadienyl)(4-nitrobenzonitrile)iron(II) iodide, [Fe(eta5-C5H5)(C7H4N2O2)(C26H4P2)]I, crystallizes in the non-centrosymmetric space group Cc, which is a promising result for obtaining quadratic non-linear optical properties. However, the packing shows that the iodide counter-ion promotes the cancellation of almost all the dipoles, resulting in a supramolecular motif of cationic chains aligned in opposite directions making an angle of 35.2 degrees. The use of PF6- as counter-ion induces the crystallization of the complex in a centrosymmetric space group. These results show that the introduction of different counter-ions, of different size and geometry, allows specific and directional intermolecular interactions that can determine the formation of a particular type of crystal packing.
authors.affiliation: Centro de Química Estrutural, Instituto Superior Técnico, Avenida Rovisco Pais, 1049-001 Lisboa, Portugal. teresa.duarte@ist.utl.pt
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Duarte
authors.forename: M Fátima M
authors.initials: MF
authors.lastname: Piedade
authors.forename: M Paula
authors.initials: MP
authors.lastname: Robalo
authors.forename: C
authors.initials: C
authors.lastname: Jacob
authors.forename: M Helena
authors.initials: MH
authors.lastname: Garcia