Publications > Martínez-Laguna et al
Alkanes C(1)-C(6) C-H Bond Activation via a Barrierless Potential Energy Path: Trifluoromethyl Carbenes Enhance Primary C-H Bond Functionalization.
1. Departamento de Química and Laboratorio de Catálisis Homogénea, Unidad Asociada al CSIC, CIQSO-Centro de Investigación en Química Sostenible, Universidad de Huelva, Huelva 21007, Spain. 2. Departamento de Química Orgánica y Química Inorgánica, Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, Alcalá de Henares, Madrid 28805, Spain. 3. The Barcelona Institute of Science and Technology, Institute of Chemical Research of Catalonia (ICIQ-CERCA), Avgda. Països Catalans, 16, Tarragona 43007, Spain. 4. Departament de Química, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain.
Abstract
In this mixed computational and experimental study, we report a catalytic system for alkane C(1)-C(6) functionalization in which the responsible step for C-H bond activation shows no barrier in the potential energy path. DFT modeling of three silver-based catalysts and four diazo compounds led to the conclusion that the Tp(F)Ag═C(H)CF(3) (Tp(F) = fluorinated trispyrazolylborate ligand) carbene intermediates interact with methane without a barrier in the potential energy surface, a prediction validated by experimentation using N(2)═C(H)CF(3) as the carbene source. The array of alkanes from propane to n-hexane led to the preferential functionalization of the primary sites with unprecedented values of selectivity for an acceptor diazo compound. The lack of those barriers implies that selectivity can no longer be controlled by differences in the energy barriers. Molecular dynamics calculations (with propane as the model alkane) are consistent with the preferential functionalization of the primary sites due to a higher concentration of such C-H bonds in the vicinity of the carbenic carbon atom.