achieved, differ only in the anion, their thermal spincrossover behavior differs considerably; on the other hand, the LIESST(L + H) behavior is similar in the two cases.
Experimental ProcedureThe ligdnd mtz was prepared as described in the literature [16]. In order to synthesize 1, iron powder was first dissolved in aqueous 2 M trifluoromethanesulfonic acid (Aldrich). The excess iron powder was then filtered off and the solution was gently concentrated under nitrogen until [Fe(H,O),](CF,SO,), began to crystallize. The product was collected by filtration and washed with a small amount of cold water and ether. Complex 1 was obtained from a concentrated aqueoussolutionof [Fe(H,O),](CF,SO,), and mtzin amolar ratio of 1 :6 under nitrogen; the solution was further concentrated by applying a stream of oxygen-free nitrogen until 1 began to crystallize. After filtration and washing, 1 was recrystallized from nitromethane. The values of the elemental analyses are in good agreement with the theoretical values. The magnetic susceptibility 1 was measured with a Foner magnetometer in the range 20 I T 5 270 K (He-flow cryostat) in a magnetic field of 1 T. The diamagnetic correction for l was determined by 1 measurement at room temperature on an analogously prepared zinc complex (% = -648 x cm'mol-'). The value of the magnetic moment was calculated from the equation pCrr = 2.828 (rm'T)"2 (1, = corrected molar susceptibility). 57Fe Mossbauer spectra were recorded with a conventional spectrometer. The "Co/Rh source was kept at room temperature, while the absorber (enclosed in a Plexiglass container, 3 cm2 area, with ca. 7 mgcm-, Fe) was mounted in a flow cryostat (CF 506, Oxford Instruments). The cryostat was equipped with windows of transparent Mylar film. The temperature at the absorber was measured with a carboniglass resistor mounted directly on the sample holder. The Mossbauer signals were fitted to Lorentzian curves.