Iron(III) complexes of triphenylphosphine and triphenylarsine oxides; their electron paramagnetic resonance and vibrational spectra

Abstract

E.p.r. spectra are reported for the complexes FeL₄(ClO₄)₃ and FeL₂X₃(L = Ph₃PO, X = Cl, Br, NO₃,NCS; L = Ph₃AsO, X = Cl, Br, NO₃). The spin-Hamiltonian parameters D and λ deduced from these measurements are related to the structures of the complexes; the vibrational spectra are also discussed. Results imply that the perchlorate complexes contain planar FeL₄³⁺ ions, whilst the chloride and bromide complexes possess the structure trans-[FeL₄X₂]⁺(FeX₄)^–. The nitrate and thiocyanate complexes appear to be monomeric, pentaco-ordinate systems.