Dynamic spin equilibrium is observed in a complex of the [Fe(II)-N6] type above room temperature. The Mössbauer lineshapes as function of temperature can be understood by means of the random-frequency-modulation model. Taking into accout the different Lamb-Mössbauer factors of the low- and high-spin state yields true populations of the two spin states. The transition rates follow rather well an Arrhenius law. With appropriate assumptions an activation energy ΔELH=18(1) kJmol-1 is deduced.