title: Exploring the Oxidative-Addition Pathways of Phenyl Chloride in the Presence of PdIIAbnormal N-Heterocyclic Carbene Complexes: A DFT Study.
abstract: DFT calculations were performed to elucidate the oxidative addition mechanism of the dimeric palladium(II) abnormal N-heterocyclic carbene complex 2 in the presence of phenyl chloride and NaOMe base under the framework of a Suzuki-Miyaura cross-coupling reaction. Pre-catalyst 2 undergoes facile, NaOMe-assisted dissociation, which led to monomeric palladium(II) species 5, 6, and 7, each of them independently capable of initiating oxidative addition reactions with PhCl. Thereafter, three different mechanistic routes, path a, path b, and path c, which originate from the catalytic species 5, 7, and 6, were calculated at M06-L-D3(SMD)/LANL2TZ(f)(Pd)/6-311++G**//M06-L/LANL2DZ(Pd)/6-31+G* level of theory. All studied routes suggested the rather uncommon PdII/PdIVoxidative addition mechanism to be favourable under the ambient reaction conditions. Although the Pd0/PdIIroutes are generally facile, the final reductive elimination step from the catalytic complexes were energetically formidable. The PdII/PdIVactivation barriers were calculated to be 11.3, 9.0, 26.7 kcal mol-1(ΔΔ≠GLS-D3) more favourable than the PdII/Pd0reductive elimination routes for path a, path b, and path c, respectively. Out of all the studied pathways, path a was the most feasible as it comprised of a PdII/PdIVactivation barrier of 24.5 kcal mol-1(ΔGLS-D3). To further elucidate the origin of transition-state barriers, EDA calculations were performed for some key saddle points populating the energy profiles.
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur -, 741 246, India.
authors.forename: Totan
authors.initials: T
authors.lastname: Mondal
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur -, 741 246, India.
authors.forename: Sriman
authors.initials: S
authors.lastname: De
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur -, 741 246, India.
authors.forename: Bholanath
authors.initials: B
authors.lastname: Maity
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur -, 741 246, India. koley@iiserkol.ac.in.
authors.forename: Debasis
authors.initials: D
authors.lastname: Koley
keywords: abnormal NHCs; density functional calculations; mechanism; oxidative addition; palladium