摘要:

AbstractThe application of two‐dimensional chemical exchange NMR spectroscopy to the elucidation of ligand‐exchange mechanisms in inorganic complexes is addressed. Specific examples involving inter‐ and intra‐molecular phosphine exchange in platinum and mercury complexes are given, and the generality of the technique is di

ISSN:0749-1581    

DOI:10.1002/mrc.1260271202

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract29Si and13C chemical shifts in substituted alkenyl‐ and alkynyl‐trimethylsilanes have been recorded and assigned. The13C NMR study of R‐alkynyltrimethylsilanes gave new evidence for pπ‐dπ bonding or an equivalent interaction between the bonded carbon and silicon atoms. In addition, the29Si and13C NMR spectra of XC6H4SiMe3[X =p‐CH3,p‐CH3O,m‐CH3O, H] were recorded, assigned and compared with those of the above‐me

ISSN:0749-1581    

DOI:10.1002/mrc.1260271203

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractA broad study of the59Co NMR of cobalt(III) porphyrin complexes with axial amine ligands in a variety of solvents is reported. The data are presented in tabular form, as are the numerical correlations of chemical shift, δ, and line width, ω1/2, using the Kamlet‐Taft equation. The dependence of δ and ω1/2on ligand substituents is discussed. Solvent data, including mixed solvent results, indicate that general factors such as acidity, basicity, polarity and hydrogen‐bonding capability are important, as are the specific nature of the functional groups on the ligands and the

ISSN:0749-1581    

DOI:10.1002/mrc.1260271204

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe13C NMR spectrum of 10,10‐diphenyl‐9‐phenanthrone was assigned unambiguously using 2D13C,1H shift correlated NMR spectra, optimized either for one‐bond or long‐range13C1H couplings, and 2D RELAY NMR spectra. This information allowed the structures of a number of substituted 10,10‐diphenyl‐9‐phenanthrones to be deduced from their13C NMR spectra. The results provide an insight into the mechanism of the reaction of 9‐fluorenone with chlorodi

ISSN:0749-1581    

DOI:10.1002/mrc.1260271205

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractMeasurements ofT1ρwere performed for well characterized systems in which the number and population of exchange sites are known. These systems include the chair‐to‐chair isomerization of cyclohexane‐d11, a two‐site exchange model with equal population, and thecis‐transisomerization of methyl nitrite, a general two‐site exchange model. The kinetic parameters obtained byT1ρmeasurements were compared with other published results, and the predicted and observed chemical shift difference between the two sites at low temperature were more rigorously compared. These comparisons showed that measurements ofT1ρin solution provide a convenient probe of the molecular dynamics in solution on the microsec

ISSN:0749-1581    

DOI:10.1002/mrc.1260271206

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe1H NMR spectrum (CD2Cl2) of the mesylate analogue of phendimetrazine bitartarate, a central nervous system stimulant and an anorexic drug, showed two isomers (ratio ≈︁ 17:1) differing in the stereochemistry of the N+HCH3moiety. A similar diastereomeric ratio was also noted in13C{1H} NMR spectra recorded in either CD2Cl2or in acidic D2O (pD ≈︁ 1). For the major species in CD2Cl2solution, four antiperiplanar vicinal1H1H coupling constants indicated a chair‐conformation 2,3‐trans‐1,4‐oxazine ring with equatorially oriented 2‐phenyl, 3‐methyl andN‐methyl substituents. The minor species also has the same chair conformation with equatorially oriented 2‐phenyl and 3‐methyl substituents, since the coupling constant for the minor species vicinal OCH(Ph)CH(Me)N methine protons was also antiperiplanar in magnitude. AxialN‐methyl stereochemistry was assigned to the minor species, since chemical shifts of the ring carbonsgauchetoN‐methyl (and of theN‐methyl carbon atom itself) were shifted characteristically upfield relative to absorbances for the corresponding carbons in the major [equatorialN‐methyl] species. TheR‐factor method was used to estimate an OC6C5N dihedral angle of 56.0(7)° for the major equatorialN‐methyl species in CD2Cl2solution. CP‐MAS13C NMR chemical shifts for solid‐state phendimetrazine bitartarate are the same as those for the solution‐state equatorialN‐methyl diastereomer. The oxydimethyleneaminomethyl fragment in the equatorialN‐methyl phendimetrazine chair conformation was used as a model for the corresponding fragment in the eight‐membered ring of nefopam. Comparison of OCH2CH2N+H(equatorial CH3)— and OCH2CH2N+Hvicinal coupling constants in the two rings suggests dynamic weighted averaging for th

ISSN:0749-1581    

DOI:10.1002/mrc.1260271207

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract1H and133Cs NMR self‐diffusion measurements were performed by means of the pulsed gradient spin‐echo method (PGSE) to evaluate the complex formation constants of Cs and 18‐crown‐6 and those of Cs and some ethylene glycols in D2O. The calculated complex formation constants were checked as far as possible by using similar calculations based on relaxation data. Chemical shift measurements do not allow the evaluation of complex formation constants in these systems. A cross‐check was introduced to verify the calculations based on the diffusion data. Similar investigations were performed on Na, K, Cs complexes andN‐phenylaza‐15‐crown‐5 in methanol. In this case, analysis of the diffusion data and as the relaxation rate and chemical shift data led to complex formation constants for 1:1 complexes, which is in contrast to a previous report suggesting the formation

ISSN:0749-1581    

DOI:10.1002/mrc.1260271208

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe assignments of the13C NMR signals of 2‐(bromomethyl)naphthalene (1) were derived by comparison of its spectrum with those of the α,α‐D2and 1‐D derivatives, by determination of relative spin‐lattice relaxation rates and by inspection of the13C,1H spin coupling patterns. Literature assignments of 1 and of 2‐(bromomethyl)‐6‐methylnaphthalene are corrected. The procedure by which these assignments has been obtained is critically evaluated. Very good additivity of substituent effects on chemical shifts is observed in the13C NMR spectra of 2,6‐ and 2,7‐bis(brom

ISSN:0749-1581    

DOI:10.1002/mrc.1260271209

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractSingle crystals of 4‐phenyl‐1,2,3,5‐dithiadiazolium trithiatriazinide, prepared by the reduction of S5N5+AlCl4−in SO2with, contain a trace paramagnetic impurity which is shown by EPR spectroscopy to be the dithiadiazolyl free radical. The g and14N hyperfine tensors of the radical were deduced from measurements made throughout three mutually orthogonal planes of crystallographically aligned specimens: g = (2.0011, 2.0075, 2.0197);14N(2) = (37.1, 11.3, 3.4 MHz.). Within experimental error, the two nitrogen hyperfine interaction tensors are collinear and have their maximum principal value aligned parallel togminand perpendicular to the plane of the host cation. The results are interpreted in terms of a planar π‐radical which substitutes for the planar host cation, and which has considerable unpaired spin density in N(2px) atomic orbitals directed perpendicular to the heteroc

ISSN:0749-1581    

DOI:10.1002/mrc.1260271210

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract13C NMR spectra of several isopimarane and 8‐epi‐isopimarane diterpenoids without double bonds have been recorded. The most significant effects caused by the change in the stereochemistry of the B/C rings junction are discus

ISSN:0749-1581    

DOI:10.1002/mrc.1260271211

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY