Joint Isotherm Calorimetric Titration–DFT Investigation of the Demethoxy-Amination of Fischer Carbenes

Abstract

The thermochemistry of the aminolysis of three methoxy Fischer carbenes, pentacarbonyl(phenylmethoxyalkylidene)chromium(0), molybdenum(0) and tungsten(0), was studied experimentally and theoretically with three amines, namely benzylamine, aniline and 3-pyrroline. Enthalpies of reactions were all determined by Isotherm Calorimetric Titration (ITC) in chlorobenzene at 298.15 K, which provided in almost all cases values of ΔrH larger than -15 kcal/mol suggesting energetically favourable transformations for all amines except aniline. No significant dependence of the enthalpy of reaction upon the nature of the metal atom of the carbene complex was found. Further ITC experiments confirmed the partial second-order reaction in amine. All COSMO-DFT computed enthalpies of reaction (spanning ca. -5.5 kcal/mol up to -20 kcal/mol) were found to be in excellent agreement with experimental values, while calculated Gibbs free energies suggested spontaneous processes for all reactions except the one with aniline.