scholarly journals H2 Evolution from H2O via O–H Oxidative Addition Across a 9,10-Diboraanthracene

2020 ◽  
Author(s):  
Jordan W. Taylor ◽  
William Harman
Keyword(s):  
Low Temperature ◽  
Lewis Acids ◽  
31P Nmr ◽  
Variable Temperature ◽  
Oxidative Addition ◽  
H2 Evolution ◽  
Chloride Exchange ◽  
11B Nmr

The boron-centered water reactivity of the boroauride complex ([Au(B2P2)][K(18-c-6)]; (B2P2, 9,10-bis(2-(diisopropylphosphino)- phenyl)-9,10-dihydroboranthrene) and its corresponding twoelectron oxidized complex, Au(B2P2)Cl, are presented. The tolerance of Au(B2P2)Cl towards H2O was demonstrated and subsequent hydroxide/chloride exchange was acheived in the presence of H2O and triethylamine to afford Au(B2P2)OH. Au(B2P2)]Cl and [Au(B2P2)]OH are poor Lewis acids as judged by the Gutmann-Becket method, with [Au(B2P2)]OH displaying facile hydroxide exchange between B atoms of the DBA ring as evidenced by variable temperature 31P NMR and low temperature 1H and 11B NMR. The reaction of the reduced boroauride complex [Au(B2P2)]– with 1 equivalent of H2O produces a hydride/hydroxide product, [Au(B2P2)(H)(OH)]–, that, upon addition of a second equivalent of H2O, rapidly evolves H2 to yield the dihydroxide compound, [Au(B2P2)(OH)2]–. [Au(B2P2)]Cl can be regenerated from [Au(B2P2)(OH)2]– via HCl·Et2O, providing a synthetic cycle for H2 evolution from H2O enabled by O–H oxidative addition at a diboraanthracene unit.

scholarly journals H2 Evolution from H2O via O–H Oxidative Addition Across a 9,10-Diboraanthracene

2020 ◽  
Author(s):  
Jordan W. Taylor ◽  
William Harman
Keyword(s):  
Low Temperature ◽  
Lewis Acids ◽  
31P Nmr ◽  
Variable Temperature ◽  
Oxidative Addition ◽  
H2 Evolution ◽  
Chloride Exchange ◽  
11B Nmr

The boron-centered water reactivity of the boroauride complex ([Au(B2P2)][K(18-c-6)]; (B2P2, 9,10-bis(2-(diisopropylphosphino)- phenyl)-9,10-dihydroboranthrene) and its corresponding twoelectron oxidized complex, Au(B2P2)Cl, are presented. The tolerance of Au(B2P2)Cl towards H2O was demonstrated and subsequent hydroxide/chloride exchange was acheived in the presence of H2O and triethylamine to afford Au(B2P2)OH. Au(B2P2)]Cl and [Au(B2P2)]OH are poor Lewis acids as judged by the Gutmann-Becket method, with [Au(B2P2)]OH displaying facile hydroxide exchange between B atoms of the DBA ring as evidenced by variable temperature 31P NMR and low temperature 1H and 11B NMR. The reaction of the reduced boroauride complex [Au(B2P2)]– with 1 equivalent of H2O produces a hydride/hydroxide product, [Au(B2P2)(H)(OH)]–, that, upon addition of a second equivalent of H2O, rapidly evolves H2 to yield the dihydroxide compound, [Au(B2P2)(OH)2]–. [Au(B2P2)]Cl can be regenerated from [Au(B2P2)(OH)2]– via HCl·Et2O, providing a synthetic cycle for H2 evolution from H2O enabled by O–H oxidative addition at a diboraanthracene unit.

Synthesis of 31P nmr spectroscopic study of [Ag(μ-R2PCH2PR2)3Ag]2+ (R = Me or Ph). Observation of an intramolecular "end-over-end" exchange of bridging R2PCH2PR2

1987 ◽  
Vol 65 (11) ◽  
pp. 2628-2633 ◽  
Author(s):  
Philip A. W. Dean ◽  
Jagadese J. Vittal ◽  
Radhey S. Srivastava
Keyword(s):  
Low Temperature ◽  
Good Yield ◽  
Nmr Spectra ◽  
31P Nmr ◽  
Variable Temperature ◽  
Exchange Process ◽  
Mixed Ligand ◽  
Enthalpy Of Activation ◽  
Intramolecular Exchange ◽  
New Compounds

Reaction of AgAsF6 with R2PCH2PR2 (R = Ph or Me) in a 2:3 ratio in MeNO2 or Me2CO produces the new compounds [Ag2(R2PCH2PR2)3](AsF6)2, which have been isolated in good yield. The analogous 107Ag-enriched compounds are produced using 107AgAsF6. The 2:3 compounds have interesting variable temperature 31P nmr spectra which have been studied in detail using the 107Ag-enriched compounds. The 31P nmr spectra of [107Ag2(Ph2PCH2PPh2)3](AsF6)2:[107Ag2(Me2PCH2PMe2)3](AsF6)2 mixtures at ambient probe temperature show the formation of the mixed ligand binuclear cations [107Ag2(Ph2PCH2PPh2)3−x(Me2PCH2PMe2)x]2+ (x = 1 or 2). By analogy, the two parent complexes also contain binuclear cations, and the limiting low temperature 31P nmr spectra of these can be interpreted in terms of the manxane structure, [107Ag(μ-R2PCH2PR2)3107Ag]2+. With increase in temperature, the 31P nmr spectra of the parents provide evidence for an intramolecular exchange process which is faster for R = Ph than for R = Me and which is shown to involve "end-over-end" exchange of bridging R2PCH2PR2. This type of exchange has not been observed previously for these ligands. With Me2CO as solvent, an approximate value of the enthalpy of activation for exchange is 59 kJ mol−1 for [107Ag((μ-Ph2PCH2PPh2)3107Ag]2+ and 50 kJ mol−1 for [107Ag(μ.-Me2PCH2PMe2)3107Ag]2+.

Low-Temperature Liquid-Phase Synthesis and Electrochemical Activity of α-Nickel Hydroxide with Flower-Like Micro-/Nano-Structure

2011 ◽  
Vol 347-353 ◽  
pp. 3379-3383
Author(s):  
Zhi Wei Li ◽  
Xu Xiang ◽  
Zong Min Tian
Keyword(s):  
Liquid Phase ◽  
Low Temperature ◽  
Ethylene Glycol ◽  
Nickel Hydroxide ◽  
Variable Temperature ◽  
Mixed Solvents ◽  
Reaction Medium ◽  
Electrochemical Activity ◽  
Nano Structure ◽  
Pure Phase

The synthesis of α-nickel hydroxide has been achieved via a facile liquid-phase precipitation approach, using the mixed solvents of ethylene glycol and water as reaction medium at low temperature. The XRD characterization indicates that pure phase α-Ni(OH)2can be obtained under variable temperature and pH value. The products present a flower-like micro-/nano-structure assembled with curved nanosheets. The nanosheets have the width of 100~500 nm and the thickness of 20~70 nm. The cavities are formed in the structure due to the interconnection of curved nanosheets. The solvents play a key role in the formation of Ni(OH)2with different forms. Pure phase α-Ni(OH)2can only be synthesized in the mixed solvents of ethylene glycol and water. Cyclic voltammetry was applied to test the electrochemical activity of the as-synthesized α-Ni(OH)2. The findings suggest that the α-Ni(OH)2with a micro-/nano-structure exhibits excellent electrochemical activity, which may be considered as a promising candidate of electrode material.

scholarly journals Experimental study on the compression characteristics of soft soil based on low temperature effect

2021 ◽  
Vol 9 (4B) ◽  
Author(s):  
Jian Zhang ◽  
◽  
Chunpeng Han ◽  
Jiayi Tian ◽  
Qingjie Dong ◽  
...  
Keyword(s):  
Low Temperature ◽  
Phase Change ◽  
Compression Test ◽  
Variable Temperature ◽  
Soft Soil ◽  
Test Methods ◽  
Variable Load ◽  
Compression Tests ◽  
Different Temperatures ◽  
Freezing Condition

Based on the characteristics of long annual freezing time and short suitable construction period of soft soil in cold region, this paper discusses the feasibility of foundation treatment of soft soil in freezing-thawing layer under freezing condition. The deformation characteristics of soft soil in freezing-thawing layer in Hulunbuir area in China are studied by using two compression test methods, namely, constant temperature and variable load (CTVL) test, variable temperature and variable load (VTVL) test. The compressibility indexes under different temperatures and consolidation pressures are obtained. The research shows that the freezing-thawing soft soil has large compressibility, the maximum strain of CTVL test is 19.89%, and the maximum compression of VTVL test can reach 18.16%. The results of CTVL compression tests show that when the soil temperature is in the range of severe phase change (-1.5℃-0℃), the temperature change has the greatest influence on the compression coefficient of soil. The result of VTVL compression test shows that some additional deformation occurs under the action of low temperature. The additional deformation is further increased when the soil is under high consolidation pressure and in the severe phase change (-1.5℃-0℃).

A 19F nuclear magnetic resonance and Raman spectroscopic investigation of the reaction of iodine oxide pentafluoride with the Lewis acids, antimony and arsenic pentafluoride

1978 ◽  
Vol 56 (17) ◽  
pp. 2253-2258 ◽  
Author(s):  
Morley Brownstein ◽  
Ronald J Gillespie ◽  
John P. Krasznai
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Raman Spectroscopy ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Oxygen Atom ◽  
Spectroscopic Investigation ◽  
Lewis Acids ◽  
Raman Spectroscopic ◽  
Nuclear Magnetic

The reactions of IOF5 with SbF5 and with AsF5 have been investigated at low temperature by 19F nmr and Raman spectroscopy. It was found that SbF5 forms labile 1:1 and 2:1 complexes whereas AsF5 forms only a 1:1 complex. The IOF5 is bound through its oxygen atom to the Lewis acids AsF5, SbF5, or (SbF5)2.

Article

1998 ◽  
Vol 76 (2) ◽  
pp. 213-220
Author(s):  
Mitchell D Refvik ◽  
Adrian L Schwan
Keyword(s):  
Low Temperature ◽  
Key Words ◽  
Variable Temperature ◽  
Cyanide Ion ◽  
Structural Assignment ◽  
Vt Nmr ◽  
Silylation Reaction

Lithium (E)-1-hexenesulfenate (5a) was treated with a number of TMS-X (TMS = trimethylsilyl) reagents to afford N,N-bis(trimethylsilyl)-(E)-1-hexenesulfenamide (7a) and (or) di((E)-1 hexenyl) disulfide (8), usually in low yield. The cleanest reactions, those from use of TMS-Cl (to afford 7a) and TMS-CN (which yields 8) were analyzed by variable temperature NMR. It was found that the low-temperature silylation reaction using TMS-Cl affords 7a and thiosulfinate 12 as initial products. Warming the mixture coerces the decomposition of 12. Treatment of 5a with TMS-CN also yields thiosulfinate 12 which is reduced to disulfide 8 as the temperature warms, possibly by action of cyanide ion. Evidence is presented that allows a confident structural assignment of the transient thiosulfinate 12, and mechanisms are suggested for the formation of 12. The study also led to the NMR observation of (E)-1-hexenesulfenate (5a).Key words: sulfenate, thiosulfinate, variable temperature NMR (VT NMR), silylation.

scholarly journals H/D Isotope Effects on 1H-NMR Chemical Shifts in Cyclic Heterodimers and Heterotrimers of Phosphinic and Phosphoric Acids

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1907 ◽  
Author(s):  
Valeriia V. Mulloyarova ◽  
Daria O. Ustimchuk ◽  
Aleksander Filarowski ◽  
Peter M. Tolstoy
Keyword(s):  
Chemical Shift ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
1H Nmr ◽  
31P Nmr ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Proton Chemical Shift ◽  
Steric Factors ◽  
Solvent Formation

Hydrogen-bonded heterocomplexes formed by POOH-containing acids (diphenylphosphoric 1, dimethylphosphoric 2, diphenylphosphinic 3, and dimethylphosphinic 4) are studied by the low-temperature (100 K) 1H-NMR and 31P-NMR using liquefied gases CDF3/CDF2Cl as a solvent. Formation of cyclic dimers and cyclic trimers consisting of molecules of two different acids is confirmed by the analysis of vicinal H/D isotope effects (changes in the bridging proton chemical shift, δH, after the deuteration of a neighboring H-bond). Acids 1 and 4 (or 1 and 3) form heterotrimers with very strong (short) H-bonds (δH ca. 17 ppm). While in the case of all heterotrimers the H-bonds are cyclically arranged head-to-tail, ···O=P–O–H···O=P–O–H···, and thus their cooperative coupling is expected, the signs of vicinal H/D isotope effects indicate an effective anticooperativity, presumably due to steric factors: when one of the H-bonds is elongated upon deuteration, the structure of the heterotrimer adjusts by shortening the neighboring hydrogen bonds. We also demonstrate the formation of cyclic tetramers: in the case of acids 1 and 4 the structure has alternating molecules of 1 and 4 in the cycle, while in case of acids 1 and 3 the cycle has two molecules of 1 followed by two molecules of 3.

Thermogravimetric, infrared and mass-spectroscopic analysis of the desorption of methanol, propan-1-ol, propan-2-ol and 2-methylpropan-2-ol from montmorillonite

Clay Minerals ◽  
1993 ◽  
Vol 28 (1) ◽  
pp. 123-137 ◽  
Author(s):  
C. Breen ◽  
J. J. Flynn ◽  
G. M. B. Parkes
Keyword(s):  
Thermogravimetric Analysis ◽  
Low Temperature ◽  
Ir Spectroscopy ◽  
Ir Spectra ◽  
Spectral Data ◽  
Spectroscopic Analysis ◽  
Variable Temperature ◽  
Trivalent Cation ◽  
Mass Spectral Data ◽  
Mass Spectral

AbstractThe desorption of methanol (MeOH), propan-1-ol (n-PrOH), propan-2-ol (i-PrOH) and 2-methylpropan-2-ol (t-BuOH) from Na+-, Ca2+-, Al3+-, Cr3+- and Fe3+-exchanged montmorillonite has been studied using variable temperature infrared (IR) spectroscopy and thermogravimetric analysis (TGA). Alcohol-saturated trivalent cation (M3+) exchanged samples exhibit maxima in the derivative thermograms at 20 and 110°C (MeOH), 30 and 160°C (n-PrOH), 20 and 110°C (i-PrOH) and 20, 55 and 80°C (t-BuOH). Alcohol-saturated Na+ and Ca2+-exchanged montmorillonite samples exhibit maxima at higher temperatures in the i-PrOH (20 and 140°C) and t-BuOH (30, 90 and 110°C) desorption profiles but at the same temperatures for MeOH and n-PrOH. Mass spectroscopic analysis of the vapours desorbed from the alcohol-treated samples show that the low-temperature maxima in the alcohol desorption from the M3+-exchanged clays are due to unchanged alcohol, whilst those occurring at 80°C (t-BuOH), 110°C (i-PrOH) and 160°C (n-PrOH) are due, in the main, to alkene produced from the intramolecular dehydration of the respective alcohol. Changes in the IR spectra of the adsorbed alcohols occur at temperatures which are in accord with the mass spectral data. No mass spectral evidence was found for the formation of dialkylethers via the competing intermolecular process but dimerisation and oligomerisation of t-BuOH were observed.

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