Encumbering the intramolecular π donation by using a bridge: A strategy for designing metal-free compounds to hydrogen activation

Wang, Zhixiang; Lü, Gang; Li, Haixia; Zhao, Lili

doi:10.1007/s11434-010-0005-x

Cited by 38 publications

(26 citation statements)

References 49 publications

(86 reference statements)

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“…First, the effect of the frustration provided by the methylene linker becomes evident when comparing the H 2 activation process involving the parent species 4 a with that involving H 2 B–NH 2 (aminoborane). For the latter system, the computed barrier and reaction energies (49.3 and 14.6 kcal mol −1 , respectively) render the analogous H 2 activation unfeasible . Moreover, the effect of the C 6 F 5 substituent (‐B(C 6 F 5 ) 2 , 4 i ), the strong EWG typically used in experiments, is comparable, in terms of the computed energy values, to that provided by bromide (‐BBr 2 , 4 d ) and iodide (−BI 2 , 4 e ) substituents (Δ G ≠ =18.6, 22.5, and 20.4 kcal mol −1 ; Δ G R =−1.8, −2.1, −6.9 kcal mol −1 , for the processes involving 4 i , 4 d , and 4 e , respectively).…”

Section: Resultsmentioning

confidence: 89%

Deeper Insight into the Factors Controlling H₂ Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs

Yepes

Jaque

Fernández

2016

Chemistry A European J

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H activation mediated by geminal aminoborane-based frustrated Lewis pairs (FLPs; R N-CH -BR' ) has been computationally explored within the density functional theory framework. It is found that the activation barrier of this process as well as the geometry of the corresponding transition states strongly depend on the nature of the substituents directly attached either to the acidic or the basic centers of the FLPs. The physical factors controlling the whole activation path are quantitatively described in detail by means of the activation strain model of reactivity combined with the energy decomposition analysis method. This methodology suggests a highly orbital-controlled mechanism where the degree of charge transfer cooperativity between the most important donor-acceptor orbital interactions, namely LP(N)→σ*(H ) and σ(H )→p (B), along the reaction coordinate constitutes a suitable indicator of the reaction barrier.

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Section: Resultsmentioning

confidence: 89%

Deeper Insight into the Factors Controlling H₂ Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs

Yepes

Jaque

Fernández

2016

Chemistry A European J

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“…However, replacing dicoordinated boron species with the tricoordinated boron species made the FLP‐N 2 adduct thermodynamically unfavorable . But, such structural combination (NHC─X─BR 2 ) in previously proposed FLP design proved effective (both thermodynamically and kinetically) for dihydrogen activation . Recent synthesis and isolation of NHC‐borane based intramolecular FLPs, proved efficient for CO 2 activation, which encourages us to probe systematic and rational studies of such rarely explored frameworks for the extremely challenging N 2 molecule.…”

Section: Introductionmentioning

confidence: 99%

Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

Rouf

Dai

et al. 2020

Advcd Theory and Sims

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Molecular nitrogen (N2), an abundant component of the atmosphere, is appealing for industrial value‐added products. However, its intrinsic inertness limits its activation to mainly metallic species. Environmental concerns and harsh reaction conditions have resulted in a demand for alternate nonmetallic and nontoxic routes to activate and functionalize N2 at ambient conditions. Comprehensive density functional theory (DFT) calculations are performed on N2 activation by boron species, specifically for the experimentally more accessible tricoordinated boron compounds. Subsequently designed frustrated Lewis pairs (FLPs) combining screened N‐heterocyclic carbene with boron moieties can make N2 activation both kinetically and thermodynamically favorable, displaying high potential for metal‐free N2 activation. The significant thermodynamic stability of the products stabilized by aromaticity and low activation barriers could be a breakthrough for the development of FLP chemistry on metal‐free N2 activation.

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“…We previously calibrated the good performance of the functional8 in describing weak bonding interactions and applied it to understand the catalytic role of N‐heterocyclic carbenes in the metal‐free transformation of carbon dioxide into methanol 9. In our design of FLP‐based hydrogen‐activation molecules4a and hydrogenation catalysts,4b we found that the energetic results given by M05‐2X were in good agreement with those provided by CCSD(T)4a or MP2 calculations 4b. M05‐2X (as implemented in the Gaussian 03 program)10 was thus selected for use in all of the DFT calculations.…”

Section: Methodsmentioning

confidence: 99%

Designing Metal‐Free Catalysts by Mimicking Transition‐Metal Pincer Templates

Lü

Zhao

et al. 2011

Chemistry A European J

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Whereas nature often promotes reactions by utilizing cheap and abundant light transition metals (TMs; e.g., Fe, Mn, Ni, Cu, and Zn) in enzyme active sites, the majority of man-made catalysts are based on precious heavy TMs (e.g., Ru, Rh, Ir, Pd, and Pt), despite high costs, limited availability, and contamination problems. Development of cheap, green, and effective catalysts (without precious TMs or even TMs at all) is at the forefront of chemical research. The recent discovery of metal-free reversible hydrogen activation by Stephan and co-workers facilitates direct catalytic hydrogenation.[1] On the basis of the frustrated Lewis pair (FLP) principle, [1,2,3] we designed metal-free hydrogenation catalysts computationally.[4] The metal-free catalyst 1 [4b, c] and the well-known metal-ligand bifunctional hydrogenation catalyst 2 [5] have related electronic and geometric structural features (Scheme 1). Indeed, increasing experimental evidence demonstrates the resemblance between the reactivity of TM-free compounds and TM complexes.[6] Herein, we computationally explore the design of metal-free catalysts by directly mimicking TM catalysts.The M05-2X DFT functional [7] was specifically developed to target nonbonding interactions. We previously calibrated the good performance of the functional [8] in describing weak bonding interactions and applied it to understand the catalytic role of N-heterocyclic carbenes in the metal-free transformation of carbon dioxide into methanol.[9] In our design of FLP-based hydrogen-activation molecules [4a] and hydrogenation catalysts, [4b] we found that the energetic results given by M05-2X were in good agreement with those provided by CCSD(T) [4a] or MP2 calculations.[4b] M05-2X (as implemented in the Gaussian 03 program) [10] was thus selected for use in all of the DFT calculations. All of the geometries were optimized and characterized as minima or transition states (TSs) at the M05-2X/6-31GA C H T U N G T R E N N U N G (d,p) level. The energies were then refined by using M05-2X/6-311 p) wave functions of the TSs were confirmed to be stable, which indicates the reliability of our single-referencebased calculations. The harmonic frequencies at the same level were employed for zero-point energy corrections and thermal and entropy corrections at 298.15 K and 1 atm. Bulky solvation effects were simulated by using the IEFPCM model [11] with benzene as a representative solvent. The corresponding free energies are discussed below, unless otherwise specified. For clarity, we use Lewis structure drawings to depict the electronic structures of molecules in the main text. The optimized geometries and their Cartesian coordinates are provided in the Supporting Information.We selected a new type of pincer catalyst (3 in Scheme 2) recently developed by Milstein and co-workers [12] as a template to derive TM-free analogues. Such TM pincer catalysts have intriguing electronic structures [13] (see below) and exhibit high s-bond activation reactivity (e.g., involving H À H, [12a, b] C À H, [12b]...

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Encumbering the intramolecular π donation by using a bridge: A strategy for designing metal-free compounds to hydrogen activation

Cited by 38 publications

References 49 publications

Deeper Insight into the Factors Controlling H₂ Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs

Deeper Insight into the Factors Controlling H₂ Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs

Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

Designing Metal‐Free Catalysts by Mimicking Transition‐Metal Pincer Templates

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Encumbering the intramolecular π donation by using a bridge: A strategy for designing metal-free compounds to hydrogen activation

Cited by 38 publications

References 49 publications

Deeper Insight into the Factors Controlling H2 Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs

Deeper Insight into the Factors Controlling H2 Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs

Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

Designing Metal‐Free Catalysts by Mimicking Transition‐Metal Pincer Templates

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Deeper Insight into the Factors Controlling H₂ Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs

Deeper Insight into the Factors Controlling H₂ Activation by Geminal Aminoborane‐Based Frustrated Lewis Pairs