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  • 1. Ahlstrand, David A.
    et al.
    Polukeev, Alexey V.
    Marcos, Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wendt, Ola F.
    Csp(3)-H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 8, p. 1748-1751Article in journal (Refereed)
    Abstract [en]

    Cyclometallation of 8-methylquinoline and 2-(dimethylamino)-pyridine in an iridium-based pincer complex is described. The C-H activation of 2-(dimethylamino) pyridine is not chelation assisted, which has not been described before for Csp(3)-H bonds in cyclometallation reactions. The mechanism of the cyclometallation of 2-(dimethylamino) pyridine was studied by DFT calculations and kinetic measurements.

  • 2. Jonasson, Klara J.
    et al.
    Polukeev, Alexey V.
    Marcos, Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wendt, Ola F.
    Reversible -Hydrogen and -Alkyl Elimination in PC(sp(3))P Pincer Complexes of Iridium2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 32, p. 9372-9375Article in journal (Refereed)
    Abstract [en]

    Despite significant progress in recent years, the cleavage of unstrained C(sp(3))C(sp(3)) bonds remains challenging. A CC coupling and cleavage reaction in a PC(sp(3))P iridium pincer complex is mechanistically studied; the reaction proceeds via the formation of a carbene intermediate and can be described as a competition between -hydrogen and -alkyl elimination; the latter process was observed experimentally and is an unusual way of C(sp(3))C(sp(3)) bond scission, which has previously not been studied in detail. Mechanistic details that are based upon kinetic studies, activation parameters, and DFT calculations are also discussed. A full characterization of a CC agostic intermediate is presented.

  • 3.
    Marcos Escartin, Rocío
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xue, Liqin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sanchez de Armas, Maria del Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Bicarbonate hydrogenation by iron: How the choice of solvent can reverse the reaction2016In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Article in journal (Other academic)
  • 4.
    Marcos, Rocio
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xue, Liqin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Angstromlab, Angstrom Lab, Dept Chem, Uppsala, Sweden.
    Sanchez-de-Armas, Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Uppsala Univ, Mat Theory Div, Dept Phys & Astron, Sweden.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Bicarbonate Hydrogenation Catalyzed by Iron: How the Choice of Solvent Can Reverse the Reaction2016In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 6, no 5, p. 2923-2929Article in journal (Refereed)
    Abstract [en]

    Here we report a mechanism study of the hydrogenation of bicarbonate by tetradentate phosphines iron-complexes. It is an extension of our recent study on the reverse reaction by the same type of complexes [Chem.-Eur. J. 2013, 19, 11869], with special emphasis herein on the effects of the choice of solvent. By using density functional theory we have located the most plausible mechanism and have found remarkable effects of the solvent on the reversibility of this reaction. We predict that the solvent used in experiment, MeOH, for the hydrogenation of bicarbonate to formate could be replaced to enhance the activity of the system. There is a direct correlation of the solubility of the base to favor or disfavor the hydrogenation of bicarbonate to formate.

  • 5. Polukeev, Alexey V.
    et al.
    Marcos, Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wendt, Ola F.
    Formation of a C-C double bond from two aliphatic carbons. Multiple C-H activations in an iridium pincer complex2015In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 6, no 3, p. 2060-2067Article in journal (Refereed)
    Abstract [en]

    The search for novel, atom-economic methods for the formation of C-C bonds is of crucial importance in synthetic chemistry. Especially attractive are reactions where C-C bonds are formed through C-H activation, but the coupling of unactivated, alkane-type C-sp3-H bonds remains an unsolved challenge. Here, we report iridium-mediated intramolecular coupling reactions involving up to four unactivated C-sp3-H bonds to give carbon-carbon double bonds under the extrusion of dihydrogen. The reaction described herein is completely reversible and the direction can be controlled by altering the reaction conditions. With a hydrogen acceptor present a C-C double bond is formed, while reacting under dihydrogen pressure leads to the reverse process, with some of the steps representing net C-sp3-C-sp3 bond cleavage. Mechanistic investigations revealed a conceptually-novel overall reactivity pattern where insertion or deinsertion of an Ir carbene moiety, formed via double C-H activation, into an Ir-C bond is responsible for the key C-C bond formation and cleavage steps.

  • 6. Polukeev, Alexey V.
    et al.
    Marcos, Rocio
    KTH, School of Biotechnology (BIO).
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wendt, Ola F.
    Iridium Hydride Complexes with Cyclohexyl-Based Pincer Ligands: Fluxionality and Deuterium Exchange2016In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 35, no 16, p. 2600-2608Article in journal (Refereed)
    Abstract [en]

    Two hydride compounds with aliphatic pincer ligands, (PCyP)IrH2 (PCyP = {cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane}(-) (1) and (PCyP)IrH4 (2), have been studied, with emphasis on features where such systems differ from arene-based analogues. Both compounds reveal relatively rapid exchange between alpha-C-H and Ir-H, which can occur via formation of carbene or through demetalation, with nearly equal barriers. This observation is confirmed by deuterium incorporation into the alpha-C-H position. Complex 1 can reversibly add an N-2 molecule, which competes with the alpha-agostic bond for a coordination site at iridium. The hydrogen binding mode in tetrahydride 2 is discussed on the basis of NMR and IR spectra, as well as DFT calculations. While the interpretation of the data is somewhat ambiguous, the best model seems to be a tetrahydride with minor contribution from a dihydrido-dihydrogen complex. In addition, the catalytic activity of 1 in deuterium exchange using benzene-d(6) as a deuterium source is presented.

  • 7. Polukeev, Alexey V.
    et al.
    Marcos, Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wendt, Ola F.
    Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 12, p. 4078-4086Article in journal (Refereed)
    Abstract [en]

    The hydride iridium pincer complex [(PCyP)IrH2] (PCyP=cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane, 1) reveals remarkably solvent-dependent hydride chemical shifts, isotope chemical shifts, J(HD) and T-1(min), with r(HH) increasing upon moving to more polar medium. The only known example of such behaviour (complex [(POCOP)IrH2], POCOP=2,6-(tBu(2)PO)(2)C6H3) was explained by the coordination of a polar solvent molecule to the iridium (J. Am. Chem. Soc. 2006, 128, 17114). Based on the existence of an agostic bond between -C-H and iridium in 1 in all solvents, we argue that the coordination of solvent can be rejected. DFT calculations revealed that the structures of 1 and [(POCOP)IrH2] depend on the dielectric permittivity of the medium and these compounds adopt trigonal-bipyramidal geometries in non-polar media and square-pyramidal geometries in polar media.

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