The thermodynamic properties of bis-(η5-cyclopentadienylirondicarbonyl)

The temperature dependence of the heat capacity of crystalline bis-(η5-cyclopentadienylirondicarbonyl) was studied over the temperature range 5–495 K in precision adiabatic vacuum and differential scanning calorimeters. The temperature dependence contained an anomaly (160–295 K) with a maximum at 250 K interpreted as a λ transition in the solid state. The fusion of the sample occurred at 435–491 K; it was accompanied by partial substance decomposition. The thermodynamic functions of crystalline bis-(η5-cyclopentadienylirondicarbonyl) were calculated from T→0 to 472.9 K. The enthalpy of combustion of the compound was determined in an isothermal calorimeter with a stationary bomb. The standard thermodynamic functions of its formation in the crystalline state at 298.15 K were calculated.