scholarly journals Recent Advances in Water-Tolerance in Frustrated Lewis Pair Chemistry

Synthesis ◽  
2018 ◽  
Vol 50 (09) ◽  
pp. 1783-1795 ◽  
Author(s):  
Michael Ingleson ◽  
Valerio Fasano

A water-tolerant frustrated Lewis pair (FLP) combines a sterically encumbered Lewis acid and Lewis base that in synergy are able to activate small molecules even in the presence of water. The main challenge introduced by water comes from its reversible coordination to the Lewis acid which causes a marked increase in the Brønsted acidity of water. Indeed, the oxophilic Lewis acids typically used in FLP chemistry form water adducts whose acidity can be comparable to that of strong Brønsted acids such as HCl, thus they can protonate the Lewis base component of the FLP. Irreversible proton transfer quenches the reactivity of both the Lewis acid and the Lewis base, precluding small molecule activation. This short review discusses the efforts to overcome water-intolerance in FLP systems, a topic that in less than five years has seen significant progress.1 Introduction2 Water-Tolerance (or Alcohol-Tolerance) in Carbonyl Reductions3 Water-Tolerance with Stronger Bases4 Water-Tolerant Non-Boron-Based Lewis Acids in FLP Chemistry5 Conclusions

Synthesis ◽  
2018 ◽  
Vol 50 (20) ◽  
pp. 4019-4036 ◽  
Author(s):  
Roberto Sanz ◽  
Raquel Hernández-Ruiz

Molybdenum(VI) dichloride dioxide (MoO2Cl2), and its addition complexes [MoO2Cl2(L)n; L = neutral ligand], are commercially or easily available and inexpensive transition-metal complexes based on a non-noble metal that can be applied as catalysts for various organic transformations. This short review aims to present the most significant breakthroughs in this field.1 Introduction2 Preparation and Reactivity of MoO2Cl2(L)n Complexes2.1 Synthesis and Structure2.2 Reactivity of Dichlorodioxomolybdenum(VI) Complexes3 Redox Processes Catalyzed by MoO2Cl2(L)n Complexes3.1 Deoxygenation Reactions Using Phosphorus Compounds3.2 Deoxygenation and Hydrosilylation Reactions Using Silanes3.3 Reduction Reactions Using Hydrogen3.4 Deoxygenation Reactions with Boranes and Thiols3.5 Reduction Reactions with Glycols3.6 Oxidation Reactions4 Ambiphilic Reactivity of MoO2Cl2 4.1 Amphoteric Lewis Acid–Lewis Base Catalyzed Reactions4.2 Lewis Acid Type Catalyzed Reactions5 Conclusion and Perspective


Tetrahedron ◽  
2019 ◽  
Vol 75 (5) ◽  
pp. 571-579 ◽  
Author(s):  
Jennifer Möricke ◽  
Florian Rehwinkel ◽  
Tobias Danelzik ◽  
Constantin G. Daniliuc ◽  
Birgit Wibbeling ◽  
...  

2014 ◽  
Vol 5 (3) ◽  
pp. 1082-1090 ◽  
Author(s):  
Gang Lu ◽  
Peng Zhang ◽  
Dongqing Sun ◽  
Lei Wang ◽  
Kebin Zhou ◽  
...  

Au (111) surface can serve as a Lewis acid to couple with a Lewis base (e.g. imine or nitrile) to form the Au-coupled FLP (frustrated Lewis pair, left) which can cleave H2, further achieving hydrogenation of small imines and nitriles.


2005 ◽  
Vol 83 (12) ◽  
pp. 2098-2105 ◽  
Author(s):  
Preston A Chase ◽  
Patricio E Romero ◽  
Warren E Piers ◽  
Masood Parvez ◽  
Brian O Patrick

Perfluorinated 9-phenyl-9-borafluorene, 1, is an antiaromatic analog of the well-known tris(pentafluorophenyl)borane. Spectroscopic, structural, and electrochemical studies have been performed on 1 and its Lewis base adducts with MeCN, THF, and PMe3 with a view to assessing its comparative Lewis acid strength relative to B(C6F5)3. For the sterically undemanding Lewis base MeCN, 1 and B(C6F5)3 have comparable LA strengths, while for more sterically prominent THF, 1 is clearly the stronger Lewis acid (LA) based on competition experiments. We conclude that steric factors, rather than antiaromaticity, are the most important determinants in the LA strength differences between 1 and B(C6F5)3.Key words: boranes, Lewis acids, fluorinated compounds, heterocycles.


2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  

Molecular electrocatalysts for CO<sub>2</sub>-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO<sub>2</sub> reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO<sub>2</sub> to form [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup>, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup>, by intramolecular cyclization of a linear [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup> species that is formed from [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup> and a second equivalent of CO<sub>2</sub>. [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup> is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex <b>Ru</b><sup>2+</sup>. The calculated activation barrier for C-O bond cleavage in [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>-1,c</sup> is dramatically decreased to 10.5 kcal mol<sup>-1</sup> from 60 kcal mol<sup>-1</sup>, the latter required for C-O bond cleavage in the linear intermediate [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup>. The intermediates are characterized experimentally by FT-IR and <sup>13</sup>C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).<br>


Author(s):  
Robert T. Cooper ◽  
Joshua S. Sapsford ◽  
Roland C. Turnell-Ritson ◽  
Dong-Hun Hyon ◽  
Andrew J. P. White ◽  
...  

Over the last decade there has been an explosion in the reactivity and applications of frustrated Lewis pair (FLP) chemistry. Despite this, the Lewis acids (LAs) in these transformations are often boranes, with heavier p -block elements receiving surprisingly little attention. The novel LA Bn 3 SnOTf ( 1 ) has been synthesized from simple, inexpensive starting materials and has been spectroscopically and structurally characterized. Subtle modulation of the electronics at the tin centre has led to an increase in its Lewis acidity in comparison with previously reported R 3 SnOTf LAs, and has facilitated low temperature hydrogen activation and imine hydrogenation. Deactivation pathways of the R 3 Sn + LA core have also been investigated. This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.


Synlett ◽  
2020 ◽  
Vol 31 (06) ◽  
pp. 535-546
Author(s):  
Sergio Rossi ◽  
Tiziana Benincori ◽  
Laura Maria Raimondi ◽  
Maurizio Benaglia

This account summarizes the development of new biheteroaromatic chiral bisphosphine oxides. 3,3′-Bithiophene-based phosphine oxides (BITIOPOs) have been successfully used as organocatalysts to promote Lewis base catalyzed, Lewis acid mediated stereoselective transformations. These highly electron-rich compounds, in combination with trichorosilyl derivatives (allyltrichlorosilane and silicon tetrachloride), generate hypervalent silicon species that act as chiral Lewis acids in highly diastereo- and enantioselective organic reactions. Several relevant examples related to these applications are discussed in detail.1 Introduction2 The BITIOPO Family3 Enantioselective Opening of Epoxides4 Enantioselective Allylation of Aldehydes5 Stereoselective Direct (Double) Aldol-Type Reaction with Ketones6 Stereoselective Direct Aldol-Type Reaction with Ester Derivatives7 Conclusions


2016 ◽  
Vol 52 (64) ◽  
pp. 9949-9952 ◽  
Author(s):  
Leif A. Körte ◽  
Sebastian Blomeyer ◽  
Shari Heidemeyer ◽  
Andreas Mix ◽  
Beate Neumann ◽  
...  

The doubly Lewis-acid functionalised aniline PhN[(CH2)3B(C6F5)2]2 features two competing boron functions in fast exchange for binding to the central Lewis base. In contrast to the mono acid-functionalised PhMeN[(CH2)3B(C6F5)2], it is an active frustrated Lewis pair.


2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  

Molecular electrocatalysts for CO<sub>2</sub>-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO<sub>2</sub> reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO<sub>2</sub> to form [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup>, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup>, by intramolecular cyclization of a linear [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup> species that is formed from [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup> and a second equivalent of CO<sub>2</sub>. [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup> is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex <b>Ru</b><sup>2+</sup>. The calculated activation barrier for C-O bond cleavage in [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>-1,c</sup> is dramatically decreased to 10.5 kcal mol<sup>-1</sup> from 60 kcal mol<sup>-1</sup>, the latter required for C-O bond cleavage in the linear intermediate [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup>. The intermediates are characterized experimentally by FT-IR and <sup>13</sup>C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).<br>


RSC Advances ◽  
2018 ◽  
Vol 8 (46) ◽  
pp. 26271-26276 ◽  
Author(s):  
Yiheng Wang ◽  
Zhen Hua Li ◽  
Huadong Wang

An oxygen-linked germinal frustrated Lewis pair was synthesized and its reactivities against a series of small molecules were investigated.


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