DFT Study of Dihydrogen Addition to Molybdenum π-Heteroaromatic Complexes: Prerequisite Step for the Catalytic Hydrodenitrogenation Processстатья
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Дата последнего поиска статьи во внешних источниках: 4 декабря 2015 г.
Аннотация:The range of molybdenum hydride complexes that are sought to participate in important catalytic hydrodenitrogenation process (HDN) of nitrogen containing polycyclic aromatic hydrocarbons were evaluated by DFT studies. Two previously synthesized stable 6-isomeric quinoline complexes of molybdenum 1C and 1N, where molubdenum atom was bound to carbocyclic and heterocyclic rings, respectively, were selected as the model molecules for this study. It was shown that the hydrogenation (HD) of organic heterocyclic ligand, which was postulated as the initial step in the overall HDN reaction, occured via consecutive steps of oxidative dihydrogen molecules addition to the Mo in 1N. Transfer of hydrogen atoms from metal to heteroaromatic ring leads to the formation of a corresponding tetrahydrido molybdenum intermediate Mo(PMe3)4H4 13 and saturated at heterocyclic ring molecule C9H11N 14.
η6, η6-Inter-ring haptotropic rearrangement (IRHR) proceeds at elevated temperatures (150 oC) in the absence of dihydrogen when kinetic isomer 1N rearranges into thermodynamically more stable isomer 1C. All proposed intermediates and transition states of described processes were calculated by DFT method and corresponding energies and the molecular geometries were optimized. The computational modeling of the HD process both for 1N and 1C, as well as IRHR as a part of larger HDN catalytic transformations provides the fundamental understanding of structure–property relationship for such mechanism.