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+.

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 and Variable Temperature 1H and 31P NMR Study of Phosphorus Ylides derived from reaction of NH-acids, triarylphosphine and acetylenic esters

2007 ◽  
Vol 2007 (6) ◽  
pp. 353-355 ◽  
Author(s):  
Seyyed Javad Sabounchei ◽  
Hassan Nemattalab
Keyword(s):  
Mass Spectroscopy ◽  
Nmr Spectra ◽  
31P Nmr ◽  
Variable Temperature ◽  
Phosphorus Ylides ◽  
Acetylenic Esters ◽  
Dialkyl Acetylenedicarboxylates ◽  
Nmr Study ◽  
One Step ◽  
C Nmr

A one-step synthesis of sterically congested phosphorus ylides in moderate to good yields by the reaction of dialkyl acetylenedicarboxylates, NH-acids and triarylphosphines are reported. Characterisation of the obtained compounds was performed by IR, 1H, 31P, 13C NMR, elemental analysis and mass spectroscopy. NMR spectra showed that some of these compounds (in CDCl3 as solvent) contained two rotamers with unequal populations that equilibrate rapidly at higher temperatures.

scholarly journals Atropisomerism of a Podophyllotoxin Derivative: Experimental and Computational Study

2018 ◽  
Vol 13 (6) ◽  
pp. 1934578X1801300
Author(s):  
Shi-Wen Zhou ◽  
Fei Jiang ◽  
Yang Yu ◽  
Xiu-Yong Huang ◽  
Yong-Heng Wang ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Nmr Spectra ◽  
Computational Study ◽  
Variable Temperature ◽  
Exchange Process ◽  
Single Bond ◽  
H Nmr ◽  
Dysosma Versipellis ◽  
Dynamic Exchange ◽  
C Nmr

Diphyllin-7′- O-β-D-glucoside, a podophyllotoxin derivative, was isolated from the roots of Dysosma versipellis. The 1H and 13C NMR spectra acquired at 300 K exhibited doubling of signals, suggesting the existence of two rotamers in solution. Variable-temperature 1H NMR experiments indicated a dynamic exchange process between the two rotamers. DFT calculations verified nearly equal energies for the two rotamers about the single bond C7′-O7.

A 31P nmr spectroscopic study of complexation of tin(II) and lead(II) by some phosphines, phosphine oxides, and related ligands, with the 31P nuclear magnetic resonance spectra of two tetratertiary phosphine tetraoxides and the analogous tetra-sulfides and -selenides

1981 ◽  
Vol 59 (1) ◽  
pp. 50-61 ◽  
Author(s):  
Philip A. W. Dean ◽  
Donald D. Phillips ◽  
Lijana Polensek
Keyword(s):  
Nmr Spectra ◽  
31P Nmr ◽  
Coupling Constants ◽  
Phosphine Oxides ◽  
Polydentate Ligands ◽  
Intramolecular Exchange ◽  
Nuclear Magnetic Resonance Spectra ◽  
Reduced Temperature

31P nmr has been used to show that, in MeNO2, M(SbF6)2 (M = Sn or Pb) forms 1:1 complexes with Ph2P(CH2)2PPh2, PhP[(CH2)2PPh2]2, MeC(CH2PPh2)3, [Formula: see text][Formula: see text]P[(CH2)2PPh2]3, and Ph2P[(CH2)2PPh]2(CH2)2PPh2. The phosphonium ligands are formed in situ. Spectra characteristics of slow inter- and intramolecular exchange were obtained in all cases except, perhaps, those involving the last two ligands, which may be involved in rapid intramolecular exchange. For the first five ligands, the maximum denticity is achieved and unambiguous one-bond M(II)—31P (M = 117/119Sn or 207Pb) coupling constants are reported and discussed. In the presence of M(SbF6)2 (M = Sn or Pb). PPh3 is protonated in MeNO2, while in acetone Sn(SbF6)2 forms a 1:1 complex with PPh3 which appears to be solvent-inserted, [Sn—O—CMe2PPh3]2+.Reduced temperature 31P nmr spectroscopy has allowed the detection of 1:2 and 1:3 (M:L) complexes of OPPh3, and 1:1 complexes of Ph2P(O)(CH2)2P(O)Ph2, PhP(O)[(CH2)2P(O)Ph2]2, and (O)P[(CH2)2P(O)Ph2]3, with both tin(II) and lead(II). The 1:1 complexes with polydentate ligands are isolable; nmr shows that the maximum denticity occurs except with the last ligand which behaves in a tridentate manner. Several two-bond M—O—P coupling constants have been obtained. Also, the changes which complexation produces in the P—P couplings are compared with changes produced in the analogous phosphine complexes.The synthesis and characterization of Ph2P(E)[(CH2)2P(E)Ph]2(CH2)2P(E)Ph2 (E = S or Se) and (Se)P[(CH2)2P(Se)Ph2]3 are reported. The 31P nmr spectra of these compounds are compared with those of the parent tetraphosphines and other members of the corresponding tetraoxide–tetrachalcogenide series.

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.

Rotationsbarriere der Endgruppen bei Poly- methinoxonolen verschiedener Kettenlänge / Rotation Barrier of the End Groups of Polymethine Oxonols with Different Chain Lengths

1976 ◽  
Vol 31 (8) ◽  
pp. 1017-1018 ◽  
Author(s):  
H. Oehling ◽  
F. Baer
Keyword(s):  
Nmr Spectra ◽  
Rotation Barrier ◽  
Free Enthalpy ◽  
Temperature Dependent ◽  
Restricted Rotation ◽  
H Nmr ◽  
Enthalpy Of Activation ◽  
End Groups ◽  
Electron Contribution ◽  
Chain Lengths

Abstract Polymethine oxonols show temperature dependent 1H-NMR-spectra because of restricted rotation of the end groups. The dependence of the value of the corresponding free enthalpy of activation AGt on the length of the poly-methine chain can be explained by the change of the π-electron contribution to ⊿G≠.

scholarly journals Direct Amidation to Access 3-Amido-1,8-Naphthalimides Including Fluorescent Scriptaid Analogues as HDAC Inhibitors

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1505
Author(s):  
Kyle N. Hearn ◽  
Trent D. Ashton ◽  
Rameshwor Acharya ◽  
Zikai Feng ◽  
Nuri Gueven ◽  
...  
Keyword(s):  
Optical Properties ◽  
Histone Deacetylase ◽  
Good Yield ◽  
Hdac Inhibitors ◽  
Selective Inhibitor ◽  
Imaging Studies ◽  
Highly Active ◽  
Theranostic Applications ◽  
New Compounds ◽  
Direct Amidation

Methodology to access fluorescent 3-amido-1,8-naphthalimides using direct Buchwald–Hartwig amidation is described. The protocol was successfully used to couple a number of substrates (including an alkylamide, an arylamide, a lactam and a carbamate) to 3-bromo-1,8-naphthalimide in good yield. To further exemplify the approach, a set of scriptaid analogues with amide substituents at the 3-position were prepared. The new compounds were more potent than scriptaid at a number of histone deacetylase (HDAC) isoforms including HDAC6. Activity was further confirmed in a whole cell tubulin deacetylation assay where the inhibitors were more active than the established HDAC6 selective inhibitor Tubastatin. The optical properties of these new, highly active, compounds make them amenable to cellular imaging studies and theranostic applications.

ChemInform Abstract: Comparison of Variable-Temperature 1H NMR Spectra of Five-Coordinate High-Spin (S = 5/2) Iron(III) Porphyrins and Chlorins

ChemInform ◽  
1988 ◽  
Vol 19 (36) ◽  
Author(s):  
M. J. PAWLIK ◽  
P. K. MILLER ◽  
E. P. JUN. SULLIVAN ◽  
M. A. LEVSTIK ◽  
D. A. ALMOND ◽  
...  
Keyword(s):  
1H Nmr ◽  
High Spin ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
1H Nmr Spectra

Dihydroxy-4′,5 tétraméthoxy-2′,3,7,8 flavone, et hydroxy-5 pentaméthoxy-2′,3,4′,7,8 flavone, deux nouveaux composés naturels isolés de Notholaenaaffinis (Ptéridophytes)

1979 ◽  
Vol 57 (14) ◽  
pp. 1901-1902 ◽  
Author(s):  
Maurice Jay ◽  
Jean Favre-Bonvin ◽  
Eckhard Wollenweber
Keyword(s):  
Natural Products ◽  
Nmr Spectra ◽  
New Compounds

The structures 4′,5-dihydroxy-2′,3,7,8-tetramethoxyflavone and 5-hydroxy-2′,3,4′,7,8-penta-methoxyflavone have been attributed to two new compounds isolated from a farinose exudate of Notholaenaaffinis; this result is derived from uv, ms, and nmr spectra of the natural products and their derivatives.

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