H 3tren] 3+ templated iron fluorides; synthesis, crystal structures and Mössbauer studies

Abstract

The hydrothermal synthesis, using tris-(2-ethylamino)amine ( tren) as a template, and the crystal structures of three new hybrid iron fluorides, (H 3O) 2·[H 3 tren] 2·(FeF 6) 2·(FeF 5(H 2O))·2H 2O ( I), [H 3 tren] 2·(FeF 6) 2·(FeF 2(H 2O) 4)·8H 2O ( II) and [H 3 tren] 2·(FeF 6)·(F) 3·H 2O ( III), are reported. I, II, and III are triclinic ( P-1), monoclinic ( P2 1/ c) and orthorhombic ( I222), respectively. The structure of I is built up from isolated FeF 6 and FeF 5(H 2O) distorted octahedra separated by triprotonated [H 3 tren] 3+ cations, disordered H 3O + cations and H 2O molecules. In II, Fe IIIF 6 and neutral [Fe IIF 2(H 2O) 4] octahedra form, together with [H 3 tren] 3+ cations, infinite (100) layers separated by extra water molecules. The structure of III consists of isolated and disordered FeF 6 octahedra, fluoride anions F − connected to [H 3 tren] 3+ cations and extra fluoride anions F − disordered with H 2O molecules. All [H 3 tren] 3+ cations have a “spider” type conformation. 57Fe Mössbauer characterization shows that +III valence state can only be considered for iron cations in I and III and preliminary Mössbauer results are consistent with the presence of both +II and +III valences for iron cations in II, in agreement with the crystallographic results.