Fluorinated 9-borafluorenes vs. conventional perfluoroaryl boranes — Comparative Lewis acidity

2005 ◽  
Vol 83 (12) ◽  
pp. 2098-2105 ◽  
Author(s):  
Preston A Chase ◽  
Patricio E Romero ◽  
Warren E Piers ◽  
Masood Parvez ◽  
Brian O Patrick
Keyword(s):  
Key Words ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Acid Strength ◽  
Lewis Base ◽  
Lewis Acidity ◽  
Electrochemical Studies ◽  
Steric Factors

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.

Empirical Lewis acid strengths for 135 cations bonded to oxygen

2017 ◽  
Vol 73 (5) ◽  
pp. 956-961 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Lewis Acid ◽  
Strong Correlation ◽  
Ionization Energy ◽  
Acid Strength ◽  
Lewis Base

New and updated Lewis acid strengths are listed for 135 cations bonded to oxygen for use with published Lewis base strengths. A strong correlation between Lewis acid strength and ionization energy is shown, and correlation with electronegativity is confirmed.

scholarly journals Unique reactivity of B in B[Ge9Y3]3 (Y = H, CH3, BO, CN): formation of a Lewis base

2019 ◽  
Vol 21 (42) ◽  
pp. 23301-23304
Author(s):  
G. Naaresh Reddy ◽  
Rakesh Parida ◽  
R. Inostroza-Rivera ◽  
Arindam Chakraborty ◽  
Puru Jena ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Base ◽  
Lewis Acidity ◽  
Boron Compounds ◽  
Zintl Ion ◽  
Acid Nature ◽  
Boron Center

Boron compounds usually exhibit Lewis acidity at the boron center due to the presence of vacant p-orbitals. But using Zintl-ion based groups (Ge9Y3, Y = H, CH3, BO, CN), we can alter Lewis acid nature of B to a Lewis base.

Halogeno-und Pseudohalogeno-tris(pentahaptocyclopentadienyl)uran(IV)- Komplexe als Lewis-Säuren: Darstellung und Struktur trigonal-bipyramidaler Uran-Organyle des Typs [(η5 -C5H5)3UXL] / Tris(pentahaptocyclopentadienyl)uranium(IV) Halides and Pseudohalides as Lewis-Acids: Preparation and Structure of Uranium Organyls [(η5 -C5H5)3UXL] with Trigonal-Bipyramidal Coordination

1978 ◽  
Vol 33 (12) ◽  
pp. 1393-1397 ◽  
Author(s):  
R. D. Fischer ◽  
E. Klähne ◽  
J. Kopf
Keyword(s):  
Structure Analysis ◽  
Lewis Acids ◽  
Lewis Base ◽  
Lewis Acidity ◽  
X Ray ◽  
Trigonal Bipyramidal Coordination ◽  
Trigonal Bipyramidal ◽  
Linear Alignment ◽  
Specific Reactions

Abstract The first two examples of a novel series of organo-actinide complexes, [Cp3UXL] (Cp = η5 -C5H5, X = halide or pseudohalide anion, L = uncharged Lewis base), are described. The X-ray structure analysis of the system with X = NCS and L = CH3CN confirms an almost linear alignment (H3)CCNUNCS along with the coplanarity of the three Cp ring normals. The remarkable Lewis acidity of certain Cp3UX-compounds appears to be essential for the formation of oligomeric species [Cp3UX]∞ as well as for specific reactions of monomeric CP3UX.

A Practical Method for Regioselective 5′-O-tert-Butyldimethylsilyl Deprotection of Persilylated Nucleosides by Methanolic Phosphomolybdic Acid

Synlett ◽  
2018 ◽  
Vol 29 (18) ◽  
pp. 2437-2443
Author(s):  
Shan-Shan Gong ◽  
Qi Sun ◽  
Hua-Shan Huang ◽  
Rui Kong ◽  
Xiu-An Zheng ◽  
...  
Keyword(s):  
Organic Solvent ◽  
Lewis Acid ◽  
31P Nmr ◽  
Practical Method ◽  
Phosphomolybdic Acid ◽  
Acid Strength ◽  
Lewis Acidity ◽  
Anion Cluster ◽  
Practical Synthesis

In nucleoside/nucleotide chemistry, the regioselective cleavage of 5′-O-TBS groups of persilylated nucleosides is a desired approach for structural functionalization at the 5′-position. However, efficient and practical methods for this purpose are still limited. In our research, we found that homogeneous methanolic phosphomolybdic acid (PMA) efficiently catalyzes the regioselective deprotection of 5′-O-TBS groups of a diversity of persilylated nucleoside substrates and can be applied in practical synthesis at scales of up to 15 g. 31P NMR results indicated that an anion cluster forms and the Lewis acidity of homogeneous PMA is organic-solvent dependent. The efficacy and pronounced regioselectivity of methanolic PMA occurs as a result of a lowering of the Lewis acid strength upon solvation of the molybdophosphate anions.

INFRARED SPECTRA OF COMPLEXES OF 4-PYRIDONES

1963 ◽  
Vol 41 (2) ◽  
pp. 515-521 ◽  
Author(s):  
Denys Cook
Keyword(s):  
Nitrogen Atom ◽  
Carbonyl Group ◽  
Lewis Acid ◽  
Infrared Spectra ◽  
Lewis Acids ◽  
Donor Site ◽  
Acid Strength ◽  
Ring Mode ◽  
Lower Frequencies

The infrared spectra of many complexes of Lewis acids with some 4-pyridones have been recorded. Large shifts to lower frequencies of about 100 cm−1 have been observed in a band near 1560 cm−1 as the Lewis acid strength increased. Much smaller shifts of about 5 to 10 cm−1 in a band near 1640 cm−1 were noted. The former band has therefore been designated as the carbonyl frequency, and the latter as a ring mode involving CC stretching.The donor site of 4-pyridones is therefore the carbonyl group, and not the nitrogen atom. Protonated 4-pyridones have similar spectra, and are consistent with O-, not N-protonation.

Tuning the reduction potentials of benzoquinone through the coordination to Lewis acids

2021 ◽  
Vol 23 (16) ◽  
pp. 9822-9831
Author(s):  
Brena L. Thompson ◽  
Zachariah M. Heiden
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Computational Study ◽  
Acid Strength ◽  
Reduction Potentials

This computational study investigates the nature of the interaction between benzoquinone and one and two Lewis acids by examining the influence of Lewis acid strength on the ability to alter the two reduction potentials of the coordinated benzoquinone molecule.

scholarly journals Amphoteric Lewis Acid/base Activity Enables an Unprecedented Pathway for Low-Energy C-O Cleavage in the Electrocatalytic Reduction of Carbon Dioxide

2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Density Functional ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Lewis Base ◽  
Nucleophilic Attack ◽  
Co Conversion ◽  
Energy Conserving ◽  
Ft Ir

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>

scholarly journals Hydrogen activation using a novel tribenzyltin Lewis acid

2017 ◽  
Vol 375 (2101) ◽  
pp. 20170008 ◽  
Author(s):  
Robert T. Cooper ◽  
Joshua S. Sapsford ◽  
Roland C. Turnell-Ritson ◽  
Dong-Hun Hyon ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Low Temperature ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Lewis Acidity ◽  
The Novel ◽  
Hydrogen Activation ◽  
Frustrated Lewis Pair

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’.

Sign in / Sign up

Export Citation Format

Share Document