Nitrenium Salts in Lewis Acid Catalysis

Mehta, Meera; Goicoechea, José M.

doi:10.1002/anie.201915547

Cited by 56 publications

(46 citation statements)

References 55 publications

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“…elegantly demonstrated that the naphthotriazinium cation can serve as a Lewis acid catalyst in several organic reactions (Scheme 1 c). [14] …”

Section: Methodsmentioning

confidence: 99%

“…Recently, Goicoechea et al elegantly demonstrated that the naphthotriazinium cation can serve as a Lewis acid catalyst in several organic reactions (Scheme 1 c). [14] Herein, we report on our synthesis of a new, Lewis acidic NHN cation, which is capable of cleaving Si À H bonds in silanes, when combined with a suitable Lewis base. To the best of our knowledge, it is the first example of a FLP consisting of a N-based Lewis acid, capable of cleaving an electrophilehydride (EÀH) type bond, which is relevant to numerous catalytic processes.…”

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confidence: 99%

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Frustrated Lewis Pairs Comprising Nitrogen Lewis Acids for Si–H Bond Activation

et al. 2020

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N‐heterocyclic nitrogen Lewis acids are a recent addition to the field of organic chemistry. Based on nitrenium cations, these acids where previously shown to generate Lewis adducts when combined with the appropriate Lewis bases. Herein, a triazinium‐based Lewis acid was combined with tBu3P to generate a frustrated Lewis pair (FLP) capable of cleaving, for the first time, Si−H bonds in silanes. Whereas low yields were initially encountered owing to insufficient Lewis acidity, a new nitrenium‐based Lewis acid was synthesized, and its superior Lewis acidity was experimentally and computationally confirmed. A FLP based on this acid cleaved the Si−H bond in PhSiH3, generating the triazane product in a quantitative yield. This unprecedented N−H triazane was fully characterized by multinuclear NMR techniques and single‐crystal X‐ray crystallography. A new class of compounds, N‐H triazanes display the potential capacity to participate in hydride transfer reactions.

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“…elegantly demonstrated that the naphthotriazinium cation can serve as a Lewis acid catalyst in several organic reactions (Scheme 1 c). [14] …”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Frustrated Lewis Pairs Comprising Nitrogen Lewis Acids for Si–H Bond Activation

et al. 2020

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“…Gandelman and co-workers have also expanded the range of triazolium salts, demonstrating access to aw ide variety of N-based Lewis acids. [24][25][26][27] More recently,M ehta and Goicoechia [28] as well as Gandelman [29] have exploited the Lewis acidity of triazinium salts for Lewis acid catalysis and FLP SiÀHa ctivation.…”

Section: Introductionmentioning

confidence: 99%

The Reactivity of Isomeric Nitrenium Lewis Acids with Phosphines, Carbenes, and Phosphide

Zhu

Zhou

et al. 2021

Chemistry A European J

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Alkylation of spiro[fluorene‐9,3’‐indazole] at N(1) and N(2) with tBuCl affords the nitrenium cations [C6H4N2(tBu)C(C12H8)][BF4], 1 and 2, respectively. Compound 1 converts to 2 over the temperature range 303–323 K with a free energy barrier of 28±5 kcal mol−1. Reaction of 1 with PMe3 afforded the N‐bound phosphine adduct [C6H4N(tBu)N(PMe3)C(C12H8)]BF4] 3. However, phosphines attack 2 at the para‐carbon atom of the aryl group with concurrent cleavage of N(2)−C(1) bond and proton migration to C(1) affording [(R3P)C6H3NN(tBu)CH(C12H8)][BF4] (R=Me 4, nBu 5). Analogous reactions of 1 and 2 with the carbene SIMes prompt attack at the para‐carbon with concurrent loss of H. affording the radical cation salts [(SIMes)C6H3N(tBu)NC(C12H8).][BF4] 6 and [(SIMes)C6H3NN(tBu)C(C12H8).][BF4] 7, whereas reaction of 2 with BAC gives the Lewis acid‐base adduct, [C6H4N(BAC)N(tBu)C(C12H8)][BF4] 8. Finally, reactions of 1 and 2 with KPPh2 result in electron transfer affording (PPh2)2 and the persistent radicals C6H4N(tBu)NC(C12H8). and C6H4NN(tBu)C(C12H8).. The detailed reaction mechanisms are also explored by extensive DFT calculations.

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“…25,26 Recently, group 14 and group 15 LAs were introduced in FLP chemistry including tetrylium [27][28][29][30][31][32][33] and phosphonium LAs. [34][35][36][37][38][39][40][41][42][43][44] Cationic tetrylium LAs were used with amines to effect H2 activation. Especially Stannyliums were demonstrated as promising FLP LAs due to their excellent moisture tolerance leading to efficient catalytic hydrogenation protocols with a wide range of substrate scope.…”

Section: Introductionmentioning

confidence: 99%

Investigating Tetrel based Neutral Frustrated Lewis Pairs for Hydrogen Activation

Sarkar

Das

Pati

2021

Preprint

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Tetrel Lewis acids are a prospective alternative to commonly employed neutral boranes in frustrated Lewis pair (FLP) chemistry. While cationic tetrylium Lewis acids, being isolobal and iso(valence)electronic, are a natural replacement to boranes, neutral tetrel Lewis acids allude as less trivial options due to the absence of a formally empty p orbital on the acceptor centre. Recently a series of intramolecular geminal FLPs (C2F5)3E-CH2-P(tBu)2 (E= Si, Ge, Sn) featuring neutral tetrel atoms as acceptor site, were reported for activation of small molecules including H2. In this work, through density functional theory computations, we elucidate the general mechanistic picture of H2 activation by this family of FLPs. Our findings reveal that the acceptor atom derives the required Lewis acidity utilizing the antibonding orbitals of its adjacent bonds with the individual contributions depending on the identity of the acceptor and the donor atoms. By varying the identity of the Lewis acid and Lewis base atoms and attached substituents, we unravel their interplay on the energetics of the H2 activation. We find that switching the donor site from P to N significantly affects the synchronous nature of the bond breaking/formations along the reaction pathway and as a result, N-bearing FLPs have a more favourable H2 activation profile than those with P. Our results are quantitatively discussed in detail within the framework of Activation Strain Model of reactivity along with the Energy Decomposition Analysis method. Finally, the reductive elimination decomposition route pertinent to the plausible extension of the H2 activation to catalytic hydrogenation by these FLPs is also examined.

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Nitrenium Salts in Lewis Acid Catalysis

Cited by 56 publications

References 55 publications

Frustrated Lewis Pairs Comprising Nitrogen Lewis Acids for Si–H Bond Activation

Frustrated Lewis Pairs Comprising Nitrogen Lewis Acids for Si–H Bond Activation

The Reactivity of Isomeric Nitrenium Lewis Acids with Phosphines, Carbenes, and Phosphide

Investigating Tetrel based Neutral Frustrated Lewis Pairs for Hydrogen Activation

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