C–H bond activation via concerted metalation–deprotonation at a palladium(iii) center† † Electronic supplementary information (ESI) available. CCDC 2129670–2129674. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d3sc00034f

ABSTRACT: Herein we report the direct observation of C–H bond activation at an isolated mononuclear Pd(iii) center. The oxidation of the Pd(ii) complex (MeN4)PdII(neophyl)Cl (neophyl = –CH2C(CH3)2Ph; MeN4 = N,N′-dimethyl-2,11-diaza[3.3](2,6)pyridinophane) using the mild oxidant ferrocenium hexafluorophosphate (FcPF6) yields the stable Pd(iii) complex [(MeN4)PdIII(neophyl)Cl]PF6. Upon the addition of an acetate source, [(MeN4)PdIII(neophyl)Cl]PF6 undergoes Csp2–H bond activation to yield the cyclometalated product [(MeN4)PdIII(cycloneophyl)]PF6. This metalacycle can be independently prepared, allowing for a complete characterization of both the starting and final Pd(iii) complexes. The C–H activation step can be monitored directly by EPR and UV-Vis spectroscopies, and kinetic isotope effect (KIE) studies suggest that either a pre-association step such as an agostic interaction may be rate limiting, or that the C–H activation is partially rate-limiting in conjunction with ligand rearrangement. Density functional theory calculations support that the reaction proceeds through a κ3 ligand coordination and that the flexible ligand structure is important for this transformation. Overall, this study represents the first example of discrete C–H bond activation occurring at a Pd(iii) center through a concerted metalation–deprotonation mechanism, akin to that observed for Pd(ii) and Pd(iv) centers. Herein we report the direct observation of C–H bond activation at an isolated mononuclear Pd(iii) center.

SUBMITTER: Bouley B 

PROVIDER: S-EPMC10074423 | biostudies-literature | 2023 Mar

REPOSITORIES: biostudies-literature