Dynamical Mechanism May Avoid High-Oxidation State Ir(V)–H Intermediate and Coordination Complex in Alkane and Arene C–H Activation by Cationic Ir(III) Phosphine

Abstract

Organometallic reaction mechanisms are assumed to be appropriately described by minimum energy pathways mapped out by density functional theory calculations. For the two-step oxidative addition/reductive elimination mechanism for C-H activation of methane and benzene by cationic Cp*(PMe)Ir(CH), we report quasiclassical direct dynamics simulations that demonstrate the Ir-H intermediate is bypassed in a significant amount of productive trajectories initiated from vibrationally averaged velocity distributions of oxidative addition transition states. This organometallic dynamical mechanism is akin to the σ-bond metathesis pathway but occurs on the oxidative addition/reductive elimination energy surface and blurs the line between two- and one-step mechanisms. Quasiclassical trajectories also reveal that the momentum of crossing the reductive elimination structure always induces complete alkane and arene dissociation from the Ir metal center, skipping weak C-H σ and π coordination complexes. This suggests that these weak coordination complexes after reductive elimination are not necessarily on the reaction pathway and likely result from a solvent cage.

Base-Promoted, Remote C–H Activation at a Cationic (η5-C5Me5)Ir(III) Center Involving Reversible C–C Bond Formation of Bound C5Me5

“…Transition metal mediated C–H bond activation is a very important transformation with great potential for the functionalization of hydrocarbons. Decisive mechanistic advances have been made with the investigation of electrophilic C–H bond activation at (η 5 -C 5 Me 5 )Ir(III) centers, 11 revealing, among other details, the influence of coligands, in particular their ability to act as a base to accept the generated proton. 12 Here, we targeted the synthesis of cationic (η 5 -C 5 Me 5 )Ir(III) complexes of the terphenyl phosphines 13 PMe 2 Ar Xyl 2 and PMe 2 Ar Dipp 2 (Scheme 1).…”

Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination During Au- and Pd-Catalyzed Diol Cyclization

“…27,28,29,30,31,32,33,34,35 Recently, we discovered dynamic effects in a few stoichiometric organometallic reactions. For example, in the C-H activation between methane and [Cp*(PMe3)Ir III (CH3)] + , 36 as well as the -hydrogen transfer for [Cp*Rh III (Et)(ethylene)] + , 37 despite a fully characterized intermediate on the DFT-potential energy landscape, direct dynamics simulations revealed that the intermediate is either sometimes or always skipped due to dynamical coupling of multiple reaction steps through dynamic matching or the lack of IVR. We also discovered dynamic effects, specifically dynamical pathway branching, in the reaction between Tp(NO)(PR3)W and benzene 38 as well as Cp(PMe3)2Re and ethylene.…”

Recent advancement in homogeneous functionalizations of methane

“…Mindiola课题组 [30,31] [33,34] . 此外, 他们发现 铜催化剂形成的卡宾物种也具有活化甲烷的潜力 [35] , 尽管反应的收率只有4%, 但却为发展更经济的催化体 系提供了一种新的方向.…”