Mechanistic Insight into the Hydrogen Activation by Frustrated Lewis Pairs
The combination of a Lewis acid (LA) and a Lewis base (LB) in such a way that they are prevented from forming a classical LA–LB adduct by means of steric hindrance or thermal hindrance is called a Frustrated Lewis Pair (FLP). FLPs have been shown to funct
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Mechanistic Insight into the Hydrogen Activation by Frustrated Lewis Pairs Mojgan Heshmat, Lei Liu, and Bernd Ensing
Abstract The combination of a Lewis acid (LA) and a Lewis base (LB) in such a way that they are prevented from forming a classical LA–LB adduct by means of steric hindrance or thermal hindrance is called a Frustrated Lewis Pair (FLP). FLPs have been shown to function as metal-free catalysts for small molecule activation and conversion. In this chapter, we review theoretical results from combined quantum mechanical calculations and first-principles (DFT) molecular dynamics/metadynamics simulations with the aim of understanding the mechanistic aspects of FLP reactivity. Our results are contextualized with the recently published work from other researchers. The mechanisms of H2 activation by both inter- and intramolecular FLPs are examined and the impact of water on FLP reactivity is discussed. Furthermore, the possibility of alternative mechanisms of H2 activation by activated carbonyl carbon is presented. Carbonyl carbon is activated (polarized) by complexation of the C = O group to a Lewis/Brønsted acid or formation of an Hbond with an H-bond donor in solution. Finally, an overview of applications of Lewis pair-functionalized metal–organic frameworks (MOFs) for H2 activation is given. Keywords Frustrated Lewis pairs · H2 activation · Homogeneous catalysis · Heterogeneous catalysis · DFT calculations · Ab initio molecular dynamics simulations
M. Heshmat · B. Ensing (B) Van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, 1098 XH Amsterdam, The Netherlands e-mail: [email protected] M. Heshmat CAT Catalytic Center, ITMC, RWTH Aachen University, Worringerweg 2, 52074 Aachen, Germany L. Liu (B) Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China e-mail: [email protected]; [email protected] © Springer Nature Switzerland AG 2021 J. Chris Slootweg and A. R. Jupp (eds.), Frustrated Lewis Pairs, Molecular Catalysis 2, https://doi.org/10.1007/978-3-030-58888-5_5
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Abbreviations AIMD BCF BDI Cy DABCO DFT Dipp EDA FES HOMO FMO FLP EF model ET model LA LB LUMO Me Mes MD MO MOF NMR PES Ph THF TS VdW
Ab Initio Molecular Dynamics Tris(pentafluorophenyl)borane β-Diketiminato Cyclohexyl 1,4-diazabicyclo[2.2.2]octane Density Functional Theory 2,6-Diisopropylphenyl = C6 H3 iPr2 Energy Decomposition Analysis Free Energy Surface Highest Occupied Molecular Orbital Frontier Molecular Orbital Frustrated Lewis Pair Electric Field model Electron Transfer model Lewis Acid Lewis Base Lowest Unoccupied Molecular Orbital Methyl Mesityl (2,4,6-trimethylphenyl) Molecular Dynamics Molecular Orbital Metal Organic Framework Nuclear Magnetic Resonance Potential Energy Surface Phenyl Tetrahydrofuran Transition State Van der Waals
5.1 Introduction Molecular hydrogen is an essential component in various chemical processes. For example, (i) H2 is the energy carrier in the foreseen sustainable hydrogen economy concept, and (ii) in organic synthesis, H2 is used
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