Investigation of thermal properties of the volatile carbonyl compounds of rhenium Re2(CO)10 and Re(CO)3(C5H5)

Abstract

The present work deals with the investigation of the thermal properties of two volatile rhenium compounds Re2(CO)10 and Re(CO)3(C5H5). The thermal behaviour of Re(CO)3(C5H5) in the condensed phase is studied by means of thermogravimetry and differential scanning calorimetry. Thermal decomposition of the vapour of Re2(CO)10 and Re(CO)3(C5H5) is studied in vacuum and in the presence of hydrogen and water vapour by means of insitu high-temperature mass spectrometry. The routes of vapour decomposition on a heated surface are proposed. Using Knudsen’s effusion method with mass spectrometric registration of the composition of the gas phase, and the flow method, temperature dependences of saturated vapour pressure were measured; thermodynamic parameters of the sublimation of complexes were calculated. For Re2(CO)10 we specified the data on the saturated vapour pressure using two independent methods within the temperature range below the phase transformations of the compound and the start of decomposition of complex vapour: ΔHTaver∘=(95.5±2.3)kJ·mol−1, ΔSTaver∘=(188.3±7.0)J·mol−1·K−1 (effusion method), ΔHTaver∘=(93.6±1.7)kJ·mol−1, ΔSTaver∘=(187.5±5.0)J·mol−1·K−1 (flow method). For Re(CO)3(C5H5) the thermodynamic characteristics were determined for the first time: ΔHTaver∘=(85.2±1.0)kJ·mol−1, ΔSTaver∘=(173.6±2.7)J·mol−1·K−1 (flow method).