DFT study of dihydrogen addition to molybdenum π-heteroaromatic complexes: a prerequisite step for the catalytic hydrodenitrogenation process

International audienceThe range of molybdenum hydride complexes that are sought to participate in the important catalytic hydrodenitrogenation process (HDN) of nitrogen containing polycyclic aromatic hydrocarbons were evaluated by DFT studies. The previously synthesized stable (η6-quinoline)Mo(PMe3)3 complex 1N, in which molybdenum is bonded to the heterocyclic ring, was chosen as a model. The hydrogenation of the quinone heterocycle, which was postulated as the initial step in the overall HDN reaction, is found to occur via three consecutive steps of the oxidative addition of dihydrogen to Mo in 1N. Successive transfer of hydrogen atoms from the metal to the heterocycle leads to the ultimate formation of the tetrahydrido molybdenum intermediate Mo(PMe3)4H413 and 2,2,3,3-tetrahydroquinoline C9H11N 14. All the involved intermediates and transition states have been fully characterized by DFT. This computational modeling of the hydrogenation of quinoline, as a part of extended HDN catalytic processes, provides a fundamental understanding of such mechanism

Donor-acceptor molecular oligogermanes: Novel properties and structural aspects

The linear oligogermyl amide 2, Ph3GeGeMe2NMe2, was obtained by reacting Ph3GeLi with 1, Me2Ge(Cl)NMe2. The amide 2 was used for the synthesis of molecular oligogermanes 3, Ph3GeGeMe2Ge(C6F5)3, and 4, [Ph3GeGeMe2]2Ge(C6F5)2, containing electron donor (Me, Ph) and acceptor (C6F5) groups, by using a hydrogermolysis reaction in n-hexane. The molecular structures of 3 and 4 were studied by XRD. It was shown that in a crystal 3 forms wide channels, in which the solvated nonpolar n-hexane molecule is present. The NMR (1H, 13C and 19F), optical (UV/vis absorption, luminescence) and electrochemical (cyclic voltammetry) properties of both compounds were also studied. The impact of the substitution type by the electron withdrawing groups (at the terminal position, such as in 3, or within the compound, such as in 5), on the physical properties was also studied

DFT study of inter-ring haptotropic rearrangement in CpRu+ complexes of polycyclic aromatic ligands

International audienceInter-ring haptotropic rearrangements (IRHRs) of different types are well-known phenomena in organometallic and catalytic chemistry. So far, they are reported for transition metal complexes with carbo-and heterocyclic polyaromatic hydrocarbons (PAH) of small and medium size. Here, we report DFT studies of RuCp+ shifts between neighboring six-membered rings (eta(6) reversible arrow eta(6)-IRHR) on an extra-large PAH as a model for graphene and compare it to naphthalene. Our calculations predict that eta(6) reversible arrow eta(6)-IRHRs proceed with much lower activation energy barrier of rearrangement in the case of the RuCp+ complex of eta(6)-graphene model

DFT Investigation of the η(6) ⇌ η(6)-Inter-ring Haptotropic Rearrangement of the Group 8 Metals Complexes [(graphene)MCp](+) (M = Fe, Ru, Os)

International audienceMetalcyclopentadienyl complexes (MCp) (M = Fe, Ru, Os) bound to the large polyaromatic hydrogenated hydrocarbon (PAH) CH used as a model for pristine graphene have been studied using a density functional theory (DFT) generalized gradient approximation (PBE functional) to reveal their structural features and dynamic behavior. The inter-ring haptotropic rearrangements (IRHRs) for these complexes were shown to occur via two transition states and one intermediate. The energy barriers of the η ⇌ η IRHRs of the (MCp) unit were found to be 30, 27, and 29 kcal/mol for M = Fe, Ru, and Os, respectively. These values are significantly lower than the values found previously for smaller PAHs. Both polar and nonpolar solvents were found not to affect significantly the energy barrier heights. Investigated transition metal complexes could be used in general as catalysts in the design of novel derivatives or materials with promising properties. Metalcyclopentadienyl complexes (MCp) of PAHs show catalytic properties mainly due to their structural details as well as their important characteristic of inter-ring haptotropic rearrangement. IRHRs take place usually by intramolecular mechanisms. During IRHRs, the ML organometallic groups (OMGs) undergo shifting along the PAH plane and could coordinate additional reagents, which is important for catalysis. Large PAHs such as graphene, fullerenes, and nanotubes possess intrinsic anticancer activity, and numerous arene complexes of Ru and Os have been proven to have anticancer properties as well. We suppose that coordinating Ru or Os to very large PAHs could synergistically increase the anticancer activity of resulting complexes

Aluminum Salen Complexes Modified with Unsaturated Alcohol: Synthesis, Characterization, and Their Activity towards Ring-Opening Polymerization of ε-Caprolactone and <i>D</i>,<i>L</i>-Lactide

A highly efficient one-step approach to the macromonomer synthesis using modified aluminum complexes as catalysts of ring-opening polymerization (ROP) of ε-caprolactone and D,L-lactide was developed. The syntheses, structures, and catalytic activities of a wide range of aluminum salen complexes, 3a-c, functionalized with unsaturated alcohol (HO(CH2)4OCH=CH2) are reported. X-Ray diffraction studies revealed a tetragonal pyramidal structure for 3c. Among the complexes 3a-c, the highest activity in bulk ROP of ε-caprolactone and D,L-lactide was displayed by 3b, affording polyesters with controlled molecular weights at low monomer to initiator ratios (Mn up to 15,000 g mol−1), relatively high polydispersities (Ð~1.8) and high number-average functionalities (Fn up to 85%)