title: First-Principles Molecular Dynamics Analysis of Ligand-Free Suzuki-Miyaura Cross-Coupling in Water Solvent: Oxidative Addition Step.
abstract: We investigated the oxidative addition of PhX (X = Cl, Br) to a single Pd(0) atom or a PdX-complex in water using first-principles molecular dynamics simulations, with solvent H2O molecules explicitly included in the calculation models, to clarify the origin of the extremely high reactivity of a ligand-free Pd catalyst in an aqueous solution for the Suzuki-Miyaura reaction. The free-energy profiles are estimated using blue moon ensemble sampling to include the entropy effect in chemical reactions in a water solvent. The free-energy barrier of the oxidative addition step is quite low for PhBr, whereas the barrier for PhCl is sizable, indicating that the reaction can proceed at room temperature with a high rate for PhBr but a rather low rate for PhCl. We also investigated the effect of the additional halogen anion on the Pd catalyst as a "supporting ligand". The activation barrier of the oxidative addition step is not affected by the supporting halogen ligand, but the final state is significantly destabilized, which should be important for the following transmetalation step. The solvent effect has also been investigated and discussed.
authors.forename: Teruo
authors.initials: T
authors.lastname: Hirakawa
authors.forename: Yuta
authors.initials: Y
authors.lastname: Uramoto
authors.forename: Daisuke
authors.initials: D
authors.lastname: Mimura
authors.forename: Atsuya
authors.initials: A
authors.lastname: Takeda
authors.affiliation: Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus , 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Yanagisawa
authors.affiliation: Synchrotron Radiation Research Center, Quantum Beam Science Research Directorate, National Institutes for Quantum and Radiological Science and Technology (QST) , 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan.
authors.forename: Takashi
authors.identifier: 0000-0001-5037-624X
authors.initials: T
authors.lastname: Ikeda
authors.affiliation: Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University , Katsura, Kyoto 615-8520, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Inagaki
authors.affiliation: Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University , Katsura, Kyoto 615-8520, Japan.
authors.forename: Yoshitada
authors.identifier: 0000-0003-4895-4121
authors.initials: Y
authors.lastname: Morikawa