title: 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.
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
authors.forename: Yihua
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China. chenh@iccas.ac.cn.
authors.forename: Hui
authors.initials: H
authors.lastname: Chen
keywords: ab initio calculations; density functional theory calculations; homogeneous catalysis; hydrogenation; iridium