The series Os4(µx-η2-C2Ph2)(CO)14–n (n = 0, 1, 2; x = n + 2) — Models for site-specific surface catalysts

2006 ◽  
Vol 84 (2) ◽  
pp. 176-186 ◽  
Author(s):  
John P Canal ◽  
Michael C Jennings ◽  
Glenn PA Yap ◽  
Roland K Pomeroy
Keyword(s):  
Specific Surface ◽  
Slow Rotation ◽  
Nmr Spectrum ◽  
Site Specific ◽  
H Nmr ◽  
Metal Atoms ◽  
Surface Catalysis ◽  
The Common ◽  
Exchange Surface ◽  
C Nmr

The cluster Os4(µ-η2-C2Ph2)(CO)14 (1) has been prepared from the reaction of Os4(CO)14 and C2Ph2 in CH2Cl2 at 25 °C. Other minor products include the known clusters Os3(µ3-η2-C2Ph2)(CO)10 and Os3(µ-η4-C4Ph4)(CO)9. The structure of 1 reveals an approximately planar C2Os4 skeleton with a dimetallacyclobutene ring (C—C = 1.32(4) Å) and a flat butterfly Os4 unit (Os—Os range = 2.859(2)–2.916(2) Å). The 13C{1H} NMR spectrum of 1 indicates the carbonyl ligands are rigid at room temperature. Stirring 1 in CH2Cl2 for 2 days (ambient temperature) afforded Os4(µ3-η2-C2Ph2)(CO)13 (2). The Os atoms in 2 also have an almost flat butterfly arrangement (Os—Os range = 2.7392(7)–2.8947(6) Å) with the alkyne ligand located over one of the Os3 triangles. The 13C NMR data for 2 are consistent with rapid rotation on the NMR timescale of the hinge Os(CO)3 units at 21 °C, but slow rotation at –50 °C. Heating 2 at 40 °C gave Os4(µ4-η2-C2Ph2)(CO)12 (3) after 2 days. Cluster 3 has the common butterfly arrangement of Os atoms with the C2Ph2 bound to all four metal atoms (Os—Os range = 2.7457(5)–2.8742(5) Å). The 13C{1H} NMR spectra of 3 at 21 and 90 °C indicate there is rapid CO exchange of the carbonyls of the two types of Os(CO)3 units, but not between the units. The spectrum at –90 °C indicates one of the rotations (presumed to be that involving the carbonyls of the wingtip Os(CO)3 units) is slowed on the NMR timescale. Compounds 1–3 form a unique series of clusters that have an alkyne ligand bound to two, three, and four metal atoms. Compound 1 is a model for a corner, compound 2 for a planar surface, and compound 3 a step site, in site-specific surface catalysts.Key words: osmium cluster, diphenylacetylene, dimetallacyclobutene, carbonyl exchange, surface catalysis.

21,22-Disubstituted 18α,19βH-Ursane Derivatives with Oxabicyclooctane System in Ring E

1993 ◽  
Vol 58 (1) ◽  
pp. 173-190 ◽  
Author(s):  
Eva Klinotová ◽  
Jiří Klinot ◽  
Václav Křeček ◽  
Miloš Buděšínský ◽  
Bohumil Máca
Keyword(s):  
Spectral Data ◽  
Spin Systems ◽  
Coupling Constants ◽  
Complete Analysis ◽  
Nmr Spectrum ◽  
Proton Proton ◽  
H Nmr ◽  
Proton Coupling ◽  
C Nmr

Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.

scholarly journals 1-Norbornyl cation may be in equilibrium with 2-norbornyl cation

2019 ◽  
Vol 45 ◽  
pp. 146867831986131
Author(s):  
Andrew Mamantov
Keyword(s):  
Nmr Spectrum ◽  
Future Studies ◽  
H Nmr ◽  
C Nmr

New 1H and 13C NMR 400 MHZ spectra of the 2-Nb cation under stable ion conditions, for example, in SbF5/SO2F2/SO2ClF, −80 oC, show besides the usual 1H NMR resonances at δ 4.93, 2.82, 1.85, the never before seen singlet, δ 9.63, and doublet, δ 2.97 (J2,6 = 16.6 Hz), ratio 1.00 : 1.07, proposed to be due to resonance-stabilized bridgehead 1-Nb cationic enantiomers in equilibrium with 2-Nb cation. The corresponding 13C proton-coupled NMR spectrum, −80 oC, has a C3,5,7 triplet, δ 30.45, J(CH) = 139.14 Hz, and C4 doublet, δ 37.7, J(CH) = 154.54 Hz. The C1,2,6 absorption, δ 91.04 is relatively broad, whereas previously, at −70 oC, it was a pentuplet. The 13C proton-decoupled spectrum at −80 oC shows the C4 doublet and C3,5,7 triplet collapsed to a singlet, but the C1,2,6 resonance is still broad. Analyses support the slowing exchange between resonance stabilized enantiomeric 2-cations at ≤ –159 oC. Some future studies are proposed.

Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate: crystal structure of polymeric (1,3-diazinane-2-thione)thiocyanato silver(I)

2015 ◽  
Vol 70 (8) ◽  
pp. 541-546 ◽  
Author(s):  
Muhammad Nawaz Tahir ◽  
Anvarhusein A. Isab ◽  
Fozia Afzal ◽  
Kashif Raza ◽  
Shah Muhammad ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Nmr Spectrum ◽  
Coordination Environment ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Ir And Nmr Spectroscopy ◽  
A Chain ◽  
Distorted Tetrahedral Coordination ◽  
C Nmr

AbstractSilver(I) complexes of thioureas and thiocyanate, [(Tu)AgSCN], [(Metu)AgSCN], [(Dmtu)AgSCN], [(Tmtu)(AgSCN)1.5], [(Imt)AgSCN], and [(Diaz)AgSCN] (where Tu = thiourea, Metu = N-methylthiourea, Dmtu = N,N′-dimethylthiourea, Tmtu = N,N,N′,N′-tetramethylthiourea, Imt = 1,3-imidazolidine-2-thione, and Diaz = 1,3-diazinane-2-thione), have been prepared and characterized by elemental analysis, IR and NMR spectroscopy, and thermal analysis. The crystal structure of one of them, [(Diaz)Ag(SCN)] (1), was determined by X-ray crystallography. The crystal structure of 1 shows that the complex exists in the form of a chain-like polymer comprising [Ag(μ2-Diaz)(μ2-SCN)] units. The silver atoms are bridged by μ2-thione sulfur atoms of Diaz and μ2-thiocyanate sulfur atoms. Thereby each silver atom adopts a distorted tetrahedral coordination environment comprising four sulfur atoms, two from thione and two from thiocyanate ligands. An upfield shift in the >C=S resonance of thiones in 13C NMR and a downfield shift in the N–H resonance in 1H NMR are consistent with the sulfur coordination to silver(I). The appearance of a band around 2100 cm–1 in the IR and a resonance around 125 ppm in the 13C NMR spectrum indicates the binding of thiocyanate to silver(I).

scholarly journals Total assignment of the1H and13C NMR spectra of piperovatine

1998 ◽  
Vol 14 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Willy Rendón ◽  
Galia Chávez ◽  
Myriam Meléndez-Rodríguez ◽  
Pedro Joseph-Nathan
Keyword(s):  
Chemical Shift ◽  
Chemical Shift Correlation ◽  
Nmr Spectrum ◽  
Quaternary Carbon Atom ◽  
H Nmr ◽  
Simulation Based ◽  
Complete Assignment ◽  
Nmr Methods ◽  
Unambiguous Assignment ◽  
C Nmr

Total and unambiguous assignment of the1H NMR spectrum of piperovatine [6‒(4‒methoxyphenyl)‒N‒(2‒methylpropyl)‒2,4‒hexadienamide] was carried out using conventional 1D NMR methods and spectral spin–spin simulation. Based on these data, the complete assignment of the13C NMR chemical shift values was made by a13C/1H chemical shift correlation diagram and conventional considerations for the quaternary carbon atom.

On Ruhemann's Purple

1980 ◽  
Vol 58 (3) ◽  
pp. 201-205 ◽  
Author(s):  
Donald C. Wigfield ◽  
Gerald W. Buchanan ◽  
Stephen M. Croteau
Keyword(s):  
Spectral Data ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Uv Visible ◽  
Ruhemann’S Purple ◽  
C Nmr

The 1H nmr spectrum previously reported for Ruhemann's Purple is shown to be inconsistent with the accepted structure of this material. The discrepancy with the reported 1H nmr spectrum is shown to be due to the presence of a major impurity, identified as hydrindantin. Spectra (1H nmr, 3C nmr, ir, uv–visible) of Ruhemann's Purple, its protonated analogue DYDA, and other ninhydrin relatives are reported, and structural conclusions are based on these spectral data.

scholarly journals Synthesis of Novel 3,7-Diazabicyclo[3.3.1]nonane Derivatives

2013 ◽  
Vol 16 (1) ◽  
pp. 85
Author(s):  
A.Ye. Malmakova ◽  
K.D. Praliyev ◽  
J.T. Welch ◽  
T.K. Iskakova ◽  
S.S. Ibraeva
Keyword(s):  
Spectral Characteristics ◽  
Triethylene Glycol ◽  
Chair Conformation ◽  
Primary Amines ◽  
Reaction Products ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Eluent Benzene ◽  
Bicyclic Ketones ◽  
C Nmr

<p>A series of 3-(3-ethoxypropyl)-7-heterocyclylalkyl-3,7-diazabicyclo[3.3.l]nonan-9-ones have been prepared by Mannich cyclocondensation of 1-(3-ethoxypropyl)-4-oxopiperidine with paraformaldehyde and primary amines followed by Wolff-Kischner reduction of the obtained bispidinones. The starting 1-(3-ethoxypropyl)-4-oxopiperidine was synthesized by Dickmann condensation of 3-ethoxypropylamine with ethylacrylate. The 3,7-diazabicyclo[3.3.1]nonanones were obtained in acceptable yields by condensation of 1-(3-ethoxypropyl)piperidin-4-one with primary amines: 1-(3-aminopropyl)imidazole or 1-(2-aminoethyl) piperazine and formaldehyde in the presence of acetic acid in methanol medium. Reduction of the obtained bispidinones with hydrazine hydrate was carried out in the presence of KOH in triethylene glycol at 160-170 °C for 5 hours. The syntheses were performed under the atmosphere of N<sub>2</sub>. As the reaction products are viscous oils, the column chromatography (on III activity aluminum oxide, eluent – benzene: dioxane 5:1) was used for purification of novel bicyclic ketones and bicyclic nonanes. The completion of the reactions was monitored by TLC. Methods of <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy were used to determine the structures of the substances synthesized. The prior studies have demonstrated that variation on the substituents at nitrogen atoms in 3- and 7-positions of bispidine cycle could result in the increase of biological activity and effect on compound spectral characteristics. Spatial structures of bispidinones and related bispidines were determined on the basis of the data of the <sup>13</sup>C and <sup>1</sup>H NMR spectra. A doublet of doublets of equatorial protons at C<sub>2.4 </sub>and C<sub>6.8</sub> with large geminal constants of 10.5-11 Hz and vicinal constants of 3.0-6.0 Hz in <sup>1</sup>H NMR spectrum revealed that those 3,7-diazabicyclo[3.3.1]nonane derivatives have a “chair-chair” conformation of both piperidine rings.</p>

Effects of substitution on nitrogen on barriers to rotation of cyclic amides. Part I. Investigation of the rotational barier in 4-benzoyl-1-thia-4-azacyclohex-2-ene by 1H dynamic nuclear magnetic resonance spectroscopy

1977 ◽  
Vol 55 (6) ◽  
pp. 949-957 ◽  
Author(s):  
T. Bruce Grindley ◽  
B. Mario Pinto ◽  
Walter A. Szarek
Keyword(s):  
Variable Temperature ◽  
Activation Parameters ◽  
Resonance Spectroscopy ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Chemical Shift Data ◽  
Dynamic Nuclear Magnetic Resonance ◽  
Shift Data ◽  
C Nmr

The rotational barrier in 4-benzoyl-1-thia-4-azacyclohex-2-ene has been investigated by total line-shape analysis of variable temperature 1H nmr spectra in acetonitrile-d3. Separate treatment of the vinyl and methylene signals yielded sets of values for activation parameters which were in excellent agreement. Assignment of the major and minor rotational isomers was made from chemical-shift data derived from the 13C nmr spectrum at 243 K in acetonitrile-d3.

Simultaneous Detection of Optical Isomers and the Separation of Overlapping Resonances in a 1H NMR Spectrum of (+/-)-2,2-Dimethyl-1-Phenyl-1-Propanol Using an NMR Shift Reagent

1989 ◽  
Vol 43 (7) ◽  
pp. 1168-1172 ◽  
Author(s):  
Ashok L. Cholli ◽  
Miu-Ling Lau
Keyword(s):  
High Resolution ◽  
Model Compound ◽  
Enantiomer Separation ◽  
Simultaneous Detection ◽  
Shift Reagent ◽  
Optically Active ◽  
Optical Isomers ◽  
Nmr Spectrum ◽  
H Nmr ◽  
C Nmr

The enantiomer separation and the spectral simplification of overlapped resonances in a high-resolution 1H NMR spectrum of a model compound have been successfully accomplished with the use of paramagnetic shift reagent. Both 1H and 13C NMR have been applied to determine the composition of a mixture containing optically active enantiomers of (+/-)-2,2-dimethyl-1-phenyl-1-propanol.

Accelerated hydrolysis of boronic acid in a modified poly(amidoamine) dendrimer: identification of a factor leading to the production of an impurity in boronic acid containing poly(amidoamine) dendrimers

2017 ◽  
Vol 95 (9) ◽  
pp. 984-990 ◽  
Author(s):  
Ching-Hua Tsai ◽  
Yu-Wen Fang ◽  
Hui-Ting Chen ◽  
Chai-Lin Kao
Keyword(s):  
Boronic Acid ◽  
Hydrolysis Product ◽  
Pamam Dendrimer ◽  
Primary Amines ◽  
Alizarin Red ◽  
Nmr Spectrum ◽  
H Nmr ◽  
Icp Ms ◽  
Hydrolysis Of ◽  
C Nmr

The preparation of boronic acid containing dendrimers is still a difficult task in dendrimer chemistry. In this investigation, an unanticipated hydrolysis product (4) was identified during the preparation of (G:2)-PAMAM-dendri-(4-phenyl boronic acid)14 (3) by acquiring its 1H NMR, 13C NMR, and UV–vis absorption spectra and IR spectra and comparing them with those of 4-hydroxylbenzoic acid (5). Furthermore, an Alizarin Red S staining analysis, ICP-MS, and 11B NMR spectrum indicated the lack of boronic acid in 4. Finally, treatment of 3 with hydrogen peroxide gave a product that was determined to be identical to dendrimer 4. By analyzing the formation of 4 under various conditions, the presence of numerous primary amines in a PAMAM dendrimer did accelerate the hydrolysis of peripheral boronic acid. This investigation revealed an apparent intrinsic problem that needs to be overcome during the preparation of boronic acid containing dendrimers and related boronic acid containing macromolecules.

The challenge of detecting modifications on proteins

2020 ◽  
Vol 64 (1) ◽  
pp. 135-153 ◽  
Author(s):  
Lauren Elizabeth Smith ◽  
Adelina Rogowska-Wrzesinska
Keyword(s):  
Mass Spectrometry ◽  
Protein Function ◽  
Chemical Properties ◽  
Lysine Acetylation ◽  
Mass Determination ◽  
Post Translational Modifications ◽  
Site Specific ◽  
The Common

Abstract Post-translational modifications (PTMs) are integral to the regulation of protein function, characterising their role in this process is vital to understanding how cells work in both healthy and diseased states. Mass spectrometry (MS) facilitates the mass determination and sequencing of peptides, and thereby also the detection of site-specific PTMs. However, numerous challenges in this field continue to persist. The diverse chemical properties, low abundance, labile nature and instability of many PTMs, in combination with the more practical issues of compatibility with MS and bioinformatics challenges, contribute to the arduous nature of their analysis. In this review, we present an overview of the established MS-based approaches for analysing PTMs and the common complications associated with their investigation, including examples of specific challenges focusing on phosphorylation, lysine acetylation and redox modifications.

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