Heterobinuclear Oxo-Bridged Complexes. II. Interactions of Cr^IIIOFe^III Complexes With Lewis Bases, Mössbauer Spectra and Magnetic Susceptibilities

Abstract

Equilibrium constants are reported for reaction of Lewis bases, including H₂O, with ( thf )( tpp ) CrOFe ( salmah ) in tetrahydrofuran and toluene solutions [ tpp = dianion of 5,10,15,20- tetraphenylporphyrin ; salmah = dianion of N,N?-(4-methyl-4-azaheptane-1,7-diyl) bis ( salicyli - deneimine )]. Mossbauer spectra of several ( tpp ) CrOFe (L) compounds have also been measured in order to define the spin states of the Fe^III centres (L= salmah , other tetradentate salicylideneimines, or anions of dithiocarbamates ). The variation of magnetic susceptibility with temperature for several complexes has been studied to 4.2 K, and shows evidence of antiferromagnetic coupling between chromium and iron centres . The interaction can be fitted to an isotropic coupling model for several (B)( tpp ) CrOFe ( salmah ) complexes (B is H₂O or 1-methylimidazole).