title: The mechanism of a ligand-promoted C(sp3)-H activation and arylation reaction via palladium catalysis: theoretical demonstration of a Pd(II)/Pd(IV) redox manifold.
abstract: Density functional theory (DFT) computations (BP86 and M06-L) have been utilized to elucidate the detailed mechanism of a palladium-catalyzed reaction involving pyridine-type nitrogen-donor ligands that significantly expands the scope of C(sp(3))-H activation and arylation. The reaction begins with precatalyst initiation, followed by substrate binding to the Pd(II) center through an amidate auxiliary, which directs the ensuing bicarbonate-assisted C(sp(3))-H bond activation producing five-membered-ring cyclopalladate(II) intermediates. These Pd(II) complexes further undergo oxidative addition with iodobenzene to form Pd(IV) complexes, which proceed by reductive C-C elimination/coupling to give final products of arylation. The base-assisted C(sp(3))-H bond cleavage is found to be the rate-determining step, which involves hydrogen bond interactions. The mechanism unravels the intimate involvement of the added 2-picoline ligand in every phase of the reaction, explains the isolation of the cyclopalladate intermediates, agrees with the observed kinetic hydrogen isotope effect, and demonstrates the Pd(II)/Pd(IV) redox manifold.
authors.affiliation: School of Chemistry and Chemical Engineering, University of the Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Dang
authors.forename: Shuanglin
authors.initials: S
authors.lastname: Qu
authors.forename: John W
authors.initials: JW
authors.lastname: Nelson
authors.forename: Hai D
authors.initials: HD
authors.lastname: Pham
authors.forename: Zhi-Xiang
authors.initials: ZX
authors.lastname: Wang
authors.forename: Xiaotai
authors.initials: X
authors.lastname: Wang