Experimental and Molecular Dynamics Simulation Study of the Sublimation Energetics of Cyclopentadienyltricarbonylmanganese (Cymantrene)

The standard molar enthalpy of sublimation of monoclinic cyclopentadienyltricarbonylmanganese, Mn(eta(5)-C5H5)(CO)(3), at 298.15 K, was determined as Delta H-sub(m)degrees[Mn(eta(5)-C5H5)(CO)(3)] = 75.97 +/- 0.37 kJ.mol(-1) from Knudsen effusion and Calvet-drop microcalorimetry measurements, thus considerably improving the very large inaccuracy (> 10 kJ.mol(-1)) of the published data. The obtained value was used to assess the extension of the OPLS-based all-atom force field we previously developed for iron metallocenes to manganese organometallic compounds. The modified force field was able to reproduce the volumetric properties (density and unit-cell volume) of crystalline Mn(eta(5)-C5H5)(CO)(3) with a deviation of 0.6% and the experimentally determined enthalpy of sublimation with an accuracy of 1 kJ.mol(-1). The interaction (epsilon) and atomic-diameter (sigma) parameters of the Lennard-Jones (12-6) potential function used to calculate dispersion contributions within the framework of the force field were found to be transferable from iron to manganese.