Issue 19, 2019

Understanding the differences between iron and palladium in cross-coupling reactions

Abstract

We aim at developing design principles, based on quantum chemical analyses, for a novel type of iron-based catalysts that mimic the behavior of their well-known palladium analogs in the bond activation step of cross coupling reactions. To this end, we have systematically explored C–X bond activation via oxidative addition of CH3X substrates (X = H, Cl, CH3) to model catalysts mFe(CO)4q (q = 0, −2; m = singlet, triplet) and, for comparison, Pd(PH3)2 and Pd(CO)2, using relativistic density functional theory at the ZORA-OPBE/TZ2P level. We find that the neutral singlet iron catalyst 1Fe(CO)4 activates all three C–X bonds via barriers that are lower than those for Pd(PH3)2 and Pd(CO)2. This is a direct consequence of the capability of the iron complex to engage not only in π-backdonation, but also in comparably strong σ-donation. Interestingly, whereas the palladium complexes favor C–Cl activation, 1Fe(CO)4 shows a strong preference for activating the C–H bond, with a barrier as low as 10.4 kcal mol−1. Our results suggest a high potential for iron to feature in palladium-type cross-coupling reactions.

Graphical abstract: Understanding the differences between iron and palladium in cross-coupling reactions

Supplementary files

Article information

Article type
Paper
Submitted
15 Dec 2018
Accepted
22 Feb 2019
First published
25 Feb 2019
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2019,21, 9651-9664

Understanding the differences between iron and palladium in cross-coupling reactions

X. Sun, M. V. J. Rocha, T. A. Hamlin, J. Poater and F. M. Bickelhaupt, Phys. Chem. Chem. Phys., 2019, 21, 9651 DOI: 10.1039/C8CP07671E

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