DFT Methods to Study the Reaction Mechanism of Iridium‐Catalyzed Hydrogenation of Olefins: Which Functional Should be Chosen?

Abstract

To enable the selection of more accurate computational methods for the future theoretical exploration of the reaction mechanism of Ir-catalyzed olefin hydrogenation, we compared high-level ab initio coupled cluster and DFT calculations with a simplified model of Pfaltz's Ir/P,N-type catalyst for all four previously proposed Ir(I) /Ir(III) and Ir(III) /Ir(V) mechanisms. Through the systematic assessment of the DFT performances, the DFT empirical dispersion correction (DFT-D3) is found to be indispensable for improving the accuracy of relative energies between the Ir(I) /Ir(III) and Ir(III) /Ir(V) mechanisms. After including the DFT-D3 correction, the three best performing density functionals (DFs) are B2-PLYP, BP86, and TPSSh. In these recommended DFs, the computationally more expensive double-hybrid functional B2-PLYP-D3 has a balanced and outstanding performance for calculations of the reaction barriers, reaction energies, and energy gaps between different mechanisms, whereas the less costly BP86-D3 and TPSSh-D3 methods have outstanding, but relatively less uniform performances.

Importance of Lattice Constants in QM/MM Calculations on Metal–Organic Frameworks

“…Because the QMMM 2018 code uses Gaussian 1 6 to calculate the quantum mechanical subsystem, we verified that the full-quantum mechanical results computed using CP2K and Gaussian 1 6 programs are comparable. We note that, as compared to M06-L results, the PBE functional slightly underestimates the relative energies of the Scheme complexesa finding that agrees with earlier computational studies of various Ir organometallic complexes. − Using the Gaussian 1 6 program, we also verified that the Ir-containing complexes we studied prefer the singlet spin state. Details are provided in the Supporting Information.…”

Distinct Roles of Ag(I) and Cu(II) as Cocatalysts in Achieving Positional-Selective C–H Alkenylation of Isoxazoles: A Theoretical Investigation

“…The infeasible O-coordinated complex is given in Figure S1 in the Supporting Information. Subsequently, proximal arene C7–H bond activation with a base-assisted concerted metalation/deprotonation (CMD) mechanism through a six-membered ring transition state TS1 Rh would take place to afford the rhodacycle intermediate 2 Rh , requiring an activation barrier of 20.9 kcal/mol.…”

What Makes a Good (Computed) Energy Profile?

“…With the aim of evaluating how accurate is DFT for modeling organometallic reactions, Hopmann has assessed the accuracy of a number of functional for reproducing experimental Gibbs energies of activation of eleven iridium-mediated transformations which correspond to elementary steps usually found in iridium-catalyzed chemistry [68]. Chen et al have performed a similar study for iridiumcatalyzed hydrogenation of olefins [69] and Leitner et al for ruthenium-catalyzed hydrogenation of olefins [70]. The general conclusion of these studies is that DFT is capable of giving a meaningful description of the energy landscape of the reactions analyzed, provided that dispersion corrections are included.…”