title: Structural, Kinetic, and Computational Characterization of the Elusive Arylpalladium(II)boronate Complexes in the Suzuki-Miyaura Reaction.
abstract: The existence of the oft-invoked intermediates containing the crucial Pd-O-B subunit, the "missing link", has been established in the Suzuki-Miyaura cross-coupling reaction. The use of low-temperature, rapid injection NMR spectroscopy (RI-NMR), kinetic studies, and computational analysis has enabled the generation, observation, and characterization of these highly elusive species. The ability to confirm the intermediacy of Pd-O-B-containing species provided the opportunity to clarify mechanistic aspects of the transfer of the organic moiety from boron to palladium in the key transmetalation step. Specifically, these studies establish the identity of two different intermediates containing Pd-O-B linkages, a tri-coordinate (6-B-3) boronic acid complex and a tetra-coordinate (8-B-4) boronate complex, both of which undergo transmetalation leading to the cross-coupling product. Two distinct mechanistic pathways have been elucidated for stoichiometric reactions of these complexes: (1) transmetalation via an unactivated 6-B-3 intermediate that dominates in the presence of an excess of ligand, and (2) transmetalation via an activated 8-B-4 intermediate that takes place with a deficiency of ligand.
authors.affiliation: Roger Adams Laboratory, Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States.
authors.forename: Andy A
authors.identifier: 0000-0001-6336-5566
authors.initials: AA
authors.lastname: Thomas
authors.affiliation: Roger Adams Laboratory, Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States.
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.affiliation: Roger Adams Laboratory, Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Zahrt
authors.affiliation: Roger Adams Laboratory, Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States.
authors.forename: Scott E
authors.identifier: 0000-0002-1099-9765
authors.initials: SE
authors.lastname: Denmark
mesh_terms: D001897:Boronic Acids / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D001897:Boronic Acids; D009942:Organometallic Compounds; D010165:Palladium