DFT study of chromium tricarbonyl complexes of coronene and kekulene

International audienceA quantum chemical study of the mechanism and determination of the activation barriers of intramolecular eta(6),eta(6)-inner-ring haptotropic rearrangements (IHR), consisting in moving a chromium tricarbonyl group Cr(CO)(3) from one six-membered aromatic ring to another, are carried out using the density functional theory (DFT) for the respective eta(6)-complexes of coronene I and kekulene II. The stationary states on the potential energy surface, determining the mechanism of eta(6),eta(6)-IHR, have a lower hapticity, which is of interest for catalysis because of the possibility of coordinating an additional substrate and reagent around the transition metal during the rearrangement. The processes of eta(6),eta(6)-IHR complexes I and II occur with similar energy barriers (Delta G(not equal) ae 20-25 kcal/mol) that are lower than the barriers (Delta G(not equal) ae 30 kcal/mol) of similar transformations previously calculated or measured for naphthalene complexes and a number of small polyaromatic hydrocarbons

Quantum chemical study of the structures and dynamic behavior of tricarbonyl complexes of Group 6 metals (Cr, Mo, W) with polyaromatic hydrocarbons using the density functional theory

International audienceThe quantum chemical study of the mechanism was performed for tricarbonyl eta(6)-complexes of coronene I-M and kekulene II-M (M = Cr, Mo, W) by the density functional method. The activation barriers of eta(6),eta(6)-interring haptotropic rearrangements (IHR), being the migration of the metaltricarbonyl group M(CO)(3) from one six-membered aromatic ring to another, were determined. The processes of eta(6),eta(6)-IHR in the metal tricarbonyl complexes with relatively high polycyclic aromatic hydrocarbons (PAH) I and II occur with close energy barriers (Delta G (not equal) ae 20-25 kcal mol(-1)), which are lower than the barriers (Delta G (not equal) similar to 30 kcal mol(-1)) of similar transformations measured or calculated earlier for the chromium tricarbonyl complexes of naphthalene and its derivatives and other PAH. For the molybdenum tricarbonyl complexes the activation barriers of eta(6),eta(6)-IHR decrease additionally by similar to 5 kcal mol(-1) compared to those for the chromium tricarbonyl complexes, whereas for the tungsten tricarbonyl complexes they increase again and become approximately equal to the activation barriers of similar chromium tricarbonyl complexes. All stationary states on the potential energy surface determining the mechanism of eta(6),eta(6)-IHR are characterized by a decrease in hapticity compared to the initial and final complexes

Organometallic chemistry of new carbon materials. Structure and dynamic behavior of group 6 metal tricabonyl complexes of graphene and perforated graphene: a DFT study

International audienceThe mechanism of inter-ring haptotropic rearrangements (IRHRs) was investigated by DFT for the tricarbonyl eta(6)-complexes of group 6 metals (M = Cr, Mo, W) of coronene (I-M), kekulene (II-M) and a model graphene (III-M). The computed eta(6),eta(6)-IRHR activation barriers in the middle size PAHs I-M and II-M were calculated to be substantially lower than those in the case of complexes of relatively small size PAHs such as naphthalene chromium tricarbonyl (Delta G approximate to 20-25 kcal mol(-1)vs. approximate to 30 kcal mol(-1)). The barrier is further lowered in the case of the model graphene complex III-Cr (Delta G approximate to 13 kcal mol(-1)). An even lower barrier is found for III-Mo (Delta G approximate to 10 kcal mol(-1)), whereas it slightly increases for III-W (Delta G approximate to 14 kcal mol(-1))