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Pyridine- and quinoline-derived mines as N,N‑bidentate directing groups in palladium versus platinum C−H bond activation reactions Torralvo Martín, Héctor Albert Mach, Joan Ariza Piquer, Xavier Font Bardia, Ma. Mercedes García Gómez, Jordi Granell Sanvicente, Jaime Ramón Martínez López, Manuel, 1957- Platí Compostos orgànics Nitrogen Platinum Organic compounds Nitrogen The C-H activation by Pd(II) and Pt(II) compounds of a wide range of imines related to 2-pyridinecarboxaldehyde, ArCH═NCH2(CH2)nPh (Ar = 2-pyridinyl, 2-picolinyl, 2-quinolinyl, n = 0, 1), which can be useful for bond functionalization assisted by bidentate directing groups, has been studied. The results indicate that the presence of two methyl groups at the α-carbon, relative to the imine nitrogen atom, facilitates the metalation. The heterocyclic fragment of the chelating ligand also shows a relevant influence on the full process, the cyclometalated compounds being more easily formed for the 2-picolinyl than for the 2-quinolinyl derivatives, while for the 2-pyridinyl derivatives the reaction is less favored. These effects have been found to be determinant for both palladium and platinum compounds. The preparative results can be explained by a steric enhancement of the metalation process, the reaction being strongly favored when bulky substituents are located in the proximity (α-carbon) of the coordinating nitrogen atoms (with both palladium and platinum). Furthermore, surprisingly the formation of six-membered platinacycles is especially favored. The kinetico-mechanistic studies of the C-H activation reaction, on some equivalent Pd(II) and Pt(II) coordination complexes of the family, have shown that the nature of the d8 metal center plays a determinant role in the reactivity observed. In this respect, the Pt(II) square-planar center has been found to be much more involved in the energetics of the reaction than the Pd(II) equivalent. The full process can be seen as a mechanistic continuum that goes from an electrophilic substitution (Pd(II) centers) to an oxidative addition/reductive elimination sequence (Pt(II) centers). The observation is directly associated with the fact that the Pt(II) center is prone to the existence of oxidatively added Pt(IV) hydrido complexes. 2021-01-26T09:11:13Z 2022-01-12T06:10:19Z 2021-01-12 2021-01-26T09:11:13Z info:eu-repo/semantics/article info:eu-repo/semantics/acceptedVersion 0276-7333 https://hdl.handle.net/2445/173399 706324 eng Versió postprint del document publicat a: https://doi.org/10.1021/acs.organomet.0c00703 Organometallics, 2021, vol. 40, p. 203-217 https://doi.org/10.1021/acs.organomet.0c00703 (c) American Chemical Society , 2021 info:eu-repo/semantics/openAccess 15 p. application/pdf American Chemical Society Articles publicats en revistes (Química Inorgànica i Orgànica)