LOW-TEMPERATURE MAGNETIC-ORDERING OF A SERIES OF STRUCTURALLY CHARACTERIZED CHLOROFERRATES

Iron-57 Mossbauer spectroscopic results for a new series of related ch loroferrate salts of complex ammonium cations are presented. In partic ular, spectra of materials based on FeCl4-, FeCl52-, FeCl63-, [FeCl5(H 2O)](2)-, and [FeCl5(CH3OH)](2-) anions are discussed relative to the systematics of their isomer shifts, coordination numbers, and low temp erature 3D critical ordering temperatures. The following specific syst ems have been studied by Mossbauer spectroscopy and definitively chara cterized by single-crystal X-ray analysis: [CH3NH3+](4)[FeCl6](3-)[Cl- ](A), [Me(2)N(mu-CH2CH2)(2)NMe(2)(+)][FeCl52-] (B), [H3NCH2CH2NH32+][F eCl5.H2O2-], (C), and [NH3(CH2)(6)NH32+](4)[(FeCl63-)(FeCl4-)Cl-4(-)] (D). The spectral data for these complexes are considered in the light of results of previous studies for systems such as [K2FeCl5.H2O], [Co (NH3)(6)][FeCl6], diamethyltriethylenediammoniumpentachloroferrate (E) , and the related [FeCl5.CH3OH](2-) salt (F). The critical 3D ordering temperatures are similar to 1.45, similar to 6.80, similar to 3.45, a nd less than or similar to 1.22 K for A, B, C, and D, respectively.