The standard molar enthalpy of sublimation ofη5-bis-pentamethylcyclopentadienyl iron measured with an electrically calibrated vacuum-drop sublimation microcalorimetric apparatus

Abstract

A heat-flow Calvet microcalorimeter was adapted for the measurement of sublimation enthalpies by the vacuum-drop method, with samples of masses in the range 1 mg to 5 mg. The electrically calibrated apparatus was tested by determining the enthalpies of sublimation of benzoic acid and ferrocene, at T= 298.15 K. The obtained results, ΔcrgHmo(C7H6O2) = (88.3 ± 0.5)kJ · mol−1and ΔcrgHmo(C10H10Fe)= (73.3 ± 0.1)kJ · mol−1, are in excellent agreement with the corresponding values recommended in the literature. Subsequent application of the apparatus to the determination of the enthalpy of sublimation of η5-bis-pentamethylcyclopentadyenyl iron, at T= 298.15 K, led to ΔcrgHmo(C20H30Fe) = (96.8 ± 0.6)kJ · mol−1.