scholarly journals The preferred conformation of erythro- and threo-1,2-difluorocyclododecanes

2012 ◽  
Vol 8 ◽  
pp. 1271-1278 ◽  
Author(s):  
Yi Wang ◽  
Peer Kirsch ◽  
Tomas Lebl ◽  
Alexandra M Z Slawin ◽  
David O'Hagan
Keyword(s):  
Nmr Spectroscopy ◽  
Structural Analysis ◽  
Conformational Analysis ◽  
Computational Studies ◽  
X Ray ◽  
H Nmr

Cyclododecane adopts a square-like structure with corner and edge CH2 groups. In this study erythro- and threo-1,2-difluorocyclododecanes were prepared to explore whether the two vicinal C–F bonds, with different relative configurations, preferably locate at corner/edge or edge/edge locations. Conformational analysis comparing the diastereoisomers was explored by using a combination of 19F{1H} NMR spectroscopy, computational studies and, in the case of the threo isomer, X-ray structural analysis. In the lowest energy conformers for both diastereoisomers the vicinal C–F bonds are located corner/edge, rather than edge/edge. These structures avoid placing a C–F bond endo into the ring, and appear to benefit from C–CHF–C angle widening, which relaxes 1,4-H,H transannular interactions.

Chemistry of zwitterionic penta-coordinate silicon compounds of the (ammoniomethyl)bis[glycolato(2–)-O1,O2]silicate type in aqueous and nonaqueous solution

2003 ◽  
Vol 81 (11) ◽  
pp. 1315-1325 ◽  
Author(s):  
Reinhold Tacke ◽  
Rüdiger Bertermann ◽  
Andreas Biller ◽  
Christian Burschka ◽  
Martin Penka
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Computational Chemistry ◽  
Experimental Investigations ◽  
Computational Studies ◽  
X Ray Diffraction ◽  
Model Species ◽  
Silicon Compounds ◽  
X Ray ◽  
H Nmr

The zwitterionic spirocyclic λ5Si-silicates bis[glycolato(2–)-O1,O2][(trimethylammonio)methyl]silicate ([OCH2C(O)O]2SiCH2NMe3, 3) and bis[2-methyllactato(2–)-O1,O2][(trimethylammonio)methyl]silicate ([OCMe2C(O)O]2SiCH2NMe3, 4) were synthesized by treatment of the zwitterionic λ5Si-silicate F4SiCH2NMe3 with 2 mol. equiv. of Me3SiOCR2C(O)OSiMe3 (R = H, Me) (formation of 4 mol. equiv. of Me3SiF). Compounds 3 (isolated as 3•2/3MeCN after drying in vacuo) and 4 were studied by solution 1H, 13C, and 29Si NMR spectroscopy and by solid-state VACP/MAS 13C, 15N, and 29Si NMR experiments, and the solvates 3•MeCN and 4•2MeCN were structurally characterized by single-crystal X-ray diffraction. These experimental investigations were complemented by computational studies of the zwitterions 3 and 4 and the anionic model species bis[2-methyllactato(2–)-O1,O2]hydridosilicate(1–) ([OCMe2C(O)O]2SiH–, 8). Compounds 3•2/3MeCN and 4 and their already known derivatives [OCH2C(O)O]2SiCH2NMe2H (1) and [OCMe2C(O)O]2SiCH2NMe2H (2) were studied for their dynamic behavior (Λ/Δ-enantiomerization) in solution by VT 1H NMR spectroscopy. In addition, compounds 1, 2, 3•2/3MeCN, and 4 were studied in CD3OD and D2O with 1H, 13C, and 29Si NMR experiments.Key words: penta-coordinate silicon, zwitterionic λ5Si-silicates, Λ/Δ-enantiomerism, NMR spectroscopy, computational chemistry.

Reactivity of Sodium Hexaethyl-2,4-dicarba-nido-hexaborate(1-)

1999 ◽  
Vol 64 (6) ◽  
pp. 977-985 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Hans-Jörg Schanz ◽  
Wolfgang Milius ◽  
Catherine McCammon
Keyword(s):  
Mössbauer Spectroscopy ◽  
Nmr Spectroscopy ◽  
Structural Analysis ◽  
Hydrogen Atom ◽  
Mossbauer Spectroscopy ◽  
Sandwich Complex ◽  
X Ray ◽  
Bromo Derivative ◽  
Boron Tribromide ◽  
C Nmr

Sodium hexaethyl-2,4-dicarba-nido-hexaborate(1-) (6), available from hexaethyl-2,4-dicarba- nido-hexaborane(8) (4) by deprotonation, reacts with deuterated methanol, CD3OD, to give back 4 without H/D exchange of the B-H-B hydrogen atom. The reaction of 6 with diethylboron chloride, Et2BCl, affords hexaethyl-2,4-dicarba-closo-hexaborane(6) (7), the first example of a peralkylated carborane of this type. In contrast, the reaction of 6 with boron tribromide, BBr3, leads mainly to 2,3,4,5,6,7-hexaethyl-2,4-dicarba-closo-heptaborane(7) (8), together with the corresponding 1-bromo derivative (9) and the closo-carborane 7 as side products. The reaction of two equivalents of 6 with FeCl2 gives the air-stable sandwich complex bis[hexaethyl-2,4-dicarba-nido-hexaborate(1-)]iron 10 which was characterised by X-ray structural analysis. All products were characterised by 1H, 11B and 13C NMR spectroscopy, and 57Fe Mössbauer spectroscopy was used to study 10.

scholarly journals Tautomerisation in 1-(4-Methylphenylazo)naphthalen-2-ol and 2-(4-Methylphenylazo)-4-methylphenol: A Crystallographic and 13C{1H}NMR Study

1999 ◽  
Vol 23 (3) ◽  
pp. 178-179
Author(s):  
Wendy I. Cross ◽  
Kevin R. Flower ◽  
Robin G. Pritchard
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Resonant Frequency ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Nmr Study ◽  
Acetic Acid Esters ◽  
Acid Esters ◽  
Equivalent Carbon

The acetic acid esters of 1-(4-methylphenylazo)naphthalen-2-ol 1 and 2-(4-methylphenylazo)-4-methylphenol 3 are prepared and characterised by single crystal X-ray diffraction studies and 13C{1H}NMR spectroscopy; the position of the C(2)13C resonance for the ester is used to predict the position of resonant frequency of the equivalent carbon in the parent alcohols and hence, calculate the position of the azo-hydrazone equilibrium in these compounds.

[Zn(phen)2(CX3COO)]+, X = H orCl; Influence of X on the Coordination Mode of the Carboxylate Group (phen = 1,10-Phenanthroline)

2005 ◽  
Vol 60 (10) ◽  
pp. 1049-1053 ◽  
Author(s):  
Zeanab Talaei ◽  
Ali Morsali ◽  
Ali R. Mahjoub
Keyword(s):  
Nmr Spectroscopy ◽  
Elemental Analysis ◽  
Coordination Mode ◽  
Bidentate Ligand ◽  
Carboxylate Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Coordinate Geometry ◽  
C Nmr

Two new ZnII(phen)2 complexes with trichloroacetate and acetate anions, [Zn(phen)2(CCl3COO)- (H2O)](ClO4) and [Zn(phen)2(CH3COO)](ClO4), have been synthesized and characterized by elemental analysis, IR, 1H NMR, 13C NMR spectroscopy. The single crystal X-ray data of these compounds show the Zn atoms to have six-coordinate geometry. From IR spectra and X-ray crystallography it is established that the coordination of the COO− group is different for trichloroacetate and acetate. The former acts as a monodentate whereas the latter acts as a bidentate ligand.

Estimating the energy of intramolecular bifurcated (three-centered) hydrogen bond by X-ray, IR and 1 H NMR spectroscopy, and QTAIM calculations

2018 ◽  
Vol 1163 ◽  
pp. 185-196 ◽  
Author(s):  
Andrei V. Afonin ◽  
Irina V. Sterkhova ◽  
Alexander V. Vashchenko ◽  
Mark V. Sigalov
Keyword(s):  
Hydrogen Bond ◽  
Nmr Spectroscopy ◽  
X Ray ◽  
H Nmr

scholarly journals Synthesis, Structure, and Properties of a Dinuclear Cu(II) Coordination Polymer Based on Quinoxaline and 3,3-Thiodipropionic Acid Ligands

2021 ◽  
Author(s):  
Adedibu Clement Tella ◽  
Samson Owalude ◽  
Vincent Adimula ◽  
Adetola Oladipo ◽  
Victoria Olayemi ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Nitrogen Atom ◽  
Coordination Polymer ◽  
Elemental Analysis ◽  
Catalytic Reduction ◽  
Copper Acetate ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr

Abstract The coordination polymer [Cu2(TDPH)4(QNX)].DMF, (QNX = Quinoxaline; TDPH = 3,3-thiodipropionic acid), has been prepared by reaction of copper acetate, TDPH, and quinoxaline. The compound was characterized by elemental analysis, FTIR spectroscopy, and single-crystal X-ray diffraction. The crystal is monoclinic with a P21/n space group and dimensions of a = 12.889(3) Å, b = 14.983(4) Å, c = 14.091(3) Å, α = 90 °, β = 90.200(11) °, γ = 90 °, V = 2721.18 (2) Å3, Z = 4. The ligands are hexagonally coordinated to the Cu(II) centre in the form of Cu2O4N with one nitrogen atom from the quinoxaline ligand, and four oxygen atoms from four TDPH molecules in a monodentate fashion. The Cu-Cu bond length was 2.642(1) and 2.629(1) Å for the Cu1----Cu1 and Cu2----Cu2 bonds. The QNX ligand bridged the two copper atoms. The catalytic reduction of 4-nitrophenol to 4-aminophenol using NaBH4 in the presence of [Cu2(TDPH)4(QNX)].DMF, as catalyst was completed within 11 minutes. The 4-aminophenol product was confirmed using 1H NMR spectroscopy.

Investigation of the disorder of dibromo- and dichloromethane in their tri-ortho-thymotide clathrates using X-ray diffraction and solid-state 2H NMR spectroscopy

2011 ◽  
Vol 89 (7) ◽  
pp. 854-862
Author(s):  
Glenn A. Facey ◽  
Ilia Korobkov
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Guest Molecule ◽  
Type B ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Twofold Axis ◽  
H Nmr ◽  
Heavy Atoms

The tri-ortho-thymotide (TOT) clathrates of dibromo- and dichloromethane were characterized by single crystal X-ray diffraction at 200 K and solid-state 2H NMR spectroscopy as a function of temperature. The host structure was found to be typical of other cage-type TOT clathrates. The X-ray results showed a substantial amount of disorder among the guest molecules. In both clathrates, multiple guest molecule positions could be modeled. The heavy atoms of all the guest molecule positions lie approximately in the same plane, with some out-of-plane distortion. The guest molecules were of two different types in positions symmetric about the crystallographic twofold rotation axis: type A guests, with carbon atoms well removed from the crystallographic twofold axis, and type B guests, with carbon atoms very close to the twofold axis. The 2H NMR spectra for the guests confirmed that the disorder was dynamic. The experimental results could be accounted for by the presence of three simultaneous types of molecular motion, all fast with respect to the 2H quadrupolar interaction: (i) twofold molecular flips about the molecular C2 symmetry axis, (ii) exchange between the type A and type B sites in a single plane, and (iii) a two-site libration of the plane containing the heavy atoms of the A and B guest sites with a temperature-dependent amplitude.

Sila-Pharmaka, 26. Mitt. [1]. Darstellung und Eigenschaften potentiell curarewirksamer Silicium-Verbindungen, III / Sila-Pharmaca, 26th Communication [1]. Preparation and Properties of Silicon Compounds with Potential Curare-Like Activity, III

1982 ◽  
Vol 37 (11) ◽  
pp. 1461-1471 ◽  
Author(s):  
Reinhold Tacke ◽  
Haryanto Linoh ◽  
Moayad T. Attar-Bashi ◽  
William S. Sheldrick ◽  
Ludger Ernst ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Neuromuscular Blocking ◽  
Neuromuscular Blocking Agents ◽  
X Ray Diffraction ◽  
Silicon Compounds ◽  
X Ray ◽  
Structure Activity Relationships ◽  
H Nmr ◽  
Structure Activity

The potentially curare-like silicon compounds 8a-8f wore synthesized and investigated with respect to their structure-activity relationships. The conformations of the com­pounds in the solid state and in solution were studied by X-ray diffraction analysis (8a-8e) and 1H NMR spectroscopy (8a-8f), respectively. The muscle relaxing properties of 8a-8f were investigated on the mouse. The observed structure-activity relationships are not in accordance with the classical “14 Å model” for neuromuscular blocking agents.

Rhodium(I)-Komplexe mit 2,5-Difurfurylpyrrol-Liganden / Rhodium(I) Complexes with 2,5-Difurfurylpyrrole Ligands

1988 ◽  
Vol 43 (12) ◽  
pp. 1598-1610 ◽  
Author(s):  
Ekkehard Lindner ◽  
Horst W. Schneider ◽  
Riad Fawzi ◽  
Ulrich Englert ◽  
Wolfgang Hiller
Keyword(s):  
Carbon Monoxide ◽  
Structural Analysis ◽  
Rhodium Complex ◽  
Monoclinic Space Group ◽  
Rhodium Complexes ◽  
Reaction Sequence ◽  
Sodium Salts ◽  
Proton Abstraction ◽  
X Ray ◽  
H Nmr

Abstract The 2.5-difurfurylpyrrole-O.N.O ligands 3a, b [R = CO2C2H5 (a). COCH, (b)] are obtained by reaction of the furanes l a , b with the 2,5-bis(chloromethyl)pyrrole 2 in the presence of SnCl4. Proton abstraction from 3a, b with NaH affords the sodium salts 4a-Na and 4b-Na. Exchange of the chlorine bridges in [μ-ClRh(Diol)]2 (5,5') (Diol = cyclooctadiene, norbornadiene) results in the formation of the 14-electron complexes (Diol)Rh(O.N.O) (6a,6'a). Addition of PPh3, yields the four-coordinated rhodium complexes (Diol)Rh(O.N.O)(PPh3) (7a,7'a). These compounds are also available in a reverse reaction sequence from 5,5', PPh3, and 4a-Na. The mononuclear rhodium complexes RhCl(Diol)(PPh3) (8,8') are isolated as intermediates. In 7a, 7'a the olefinic ligands are replaced by carbon monoxide to give the dicarbonyl rhodium complex (OC)2Rh(O.N.O)(PPh3) (9a) being detectable only in solution. The same result is achieved upon addition of CO to the compound (OC)Rh(O.N.O)(PPh,) (11a) which results bv the reaction of [μ-ClRh(CO)(PPh3)]2 (10) with 4a-Na. Oxidative addition of CH3I or H2 to 6a, 6 a, 7a, 7'a or 11a was not observed. 1H and 31P{1H} NMR investigations indicate that depending on the temperature the O.N.O ligand in the 14-electron rhodium complex 11a acts as tri- (11a-A), bi- (11a-B) and monodentate (IIa-C) ligands. respectively. 11a also reacts with PPh, to form the /ram-bis(phosphane)rhodium complex (PPh3)2Rh(CO)(O.N.O) (12a). 12a and the analogous complexes 12b and trans-(PMe3)2Rh(CO)(O,N.O) (14a) are obtained by action of ClRh(CO)L2 (13) (L = PPh3. PMe3) on 4a-Na and 4b-Na, respectively. The methylene bridges in the O.N.O ligand 3a are not oxidized, neither in the non-complexed (3a) nor in the complexed (12a) state. According to an X-ray structural analysis 14a crystallizes in the monoclinic space group P21/n with Z = 4. In 6a, 6'a, 7a, 7'a, 9a, 11a, 12a, b, and 14a the O.N.O ligand is always nitrogen bonded

Sign in / Sign up

Export Citation Format

Share Document