119Sn NMR Spectroscopy of Some Iron-Tin Compounds – First Measurements of One-Bond Coupling Constants 1J(119Sn57Fe), Geminal Coupling Constants 2J(119SnFe119Sn) and the Dependence of 119Sn Chemical Shifts on the Nature of the Sn–Fe Bond

1992 ◽  
Vol 47 (12) ◽  
pp. 1749-1753 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Berthold Distler ◽  
Max Herberhold
Keyword(s):  
Chemical Shifts ◽  
Coupling Constants ◽  
Large Magnitude ◽  
Tin Compounds ◽  
119Sn Nmr ◽  
Tin Complexes ◽  
Geminal Coupling ◽  
Efficient Coupling ◽  
Cyclic Compounds ◽  
First Time

Carbonyliron tin complexes CpFe(CO)2–SnMe3 (1), cis-(CO)4Fe(SnMe3)2 (2), cis-(CO)4Fe(SnMe2Cl)2 (3), [R2SnFe(CO)4]2 (4a, R = Me; 4b, R = Bu), {Me2Sn[Fe(CO)4]2}2Sn (5), Me2Sn[Fe(CO)4]2Sn[Fe(CO)4]2 (6) and Sn[Fe(CO)4]4 (7) were studied by 119Sn NMR. It proved possible for the first time to observe coupling constants 1J(119Sn57Fe) in the range of 36 to 64 Hz. The large magnitude of geminal coupling constants |2J(119SnFe119Sn)| (1400 to 1800 Hz) in the cyclic compounds 4 to 6 indicates the presence of tin-tin interactions as an efficient coupling pathway. Extreme deshielding of 119Sn nuclei in the complexes 6 (δ119Sn + 953) and 7 (δ119Sn + 1532) is associated with three-centre FeSnFe bonds in these compounds.

Eine 15N-NMR-untersuchung einiger trimethylstannylhydrazine / A15N-NMR study of some trimethylstannylhydrazines

1989 ◽  
Vol 44 (6) ◽  
pp. 653-658 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Theo Gasparis-Ebeling ◽  
Heinrich Nöth
Keyword(s):  
Nmr Spectroscopy ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Relative Magnitude ◽  
Coupling Constants ◽  
15N Nmr ◽  
Nmr Study ◽  
Geminal Coupling ◽  
In Cis ◽  
First Time

The trimethylstannylhydrazines (Me3Sn)2N-NMe2 (1), Me3Sn(Me)N-N(Me)SnMe3 (2), (Me3Sn)2N-N(Me)SnMe3 (3), and (M e3Sn)2N-N(Ph)SnMe3 (4) have been studied by δ15N NMR at natural abundance. A correlation between δ15N of hydrazines and δI5N of corresponding am ines (replacement of one N-atom by the CH-unit) is proposed in order to estimate δI5N values and to support the non-trivial assignment of 15N resonances of hydrazines. Geminal coupling constants 2J(119SnN 15N) have been observed for the first time. Their relative magnitude is related to the probability of the N-Sn bond being in cis-position with respect to the orientation of the lone electron pair at the 15N nucleus in the 119Sn-N-15N fragment. Treatment of 4 with phenylacetylene causes non-selective cleavage of the Sn-N bonds, leading to the trim ethylstannylhydrazines 5 and 6 which have been characterized by 119Sn and 15N NMR spectroscopy in solution

13C and 119Sn NMR spectra of diphenyl- and dibenzyltin(IV) compounds and their complexes

1990 ◽  
Vol 55 (5) ◽  
pp. 1193-1207 ◽  
Author(s):  
Jaroslav Holeček ◽  
Antonín Lyčka ◽  
Karel Handlíř ◽  
Milan Nádvorník
Keyword(s):  
Internal Structure ◽  
Coordination Sphere ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spectral Parameters ◽  
The Real ◽  
119Sn Nmr ◽  
C Nmr

13C and 119Sn NMR spectra of diphenyl- and dibenzyltin(IV) compounds have been studied in solutions of coordinating and non-coordinating solvents. Regions of values of the δ(119Sn) chemical shifts have been determined which characterize individual types of coordination of the central tin atom. The values of 13C NMR spectral parameters, the δ(13C) chemical shifts and nJ(119Sn, 13C) coupling constants, have been used to describe the real shapes of coordination sphere of the central tin atom and to discuss the internal structure of the organic substituents and of the nature of their bonding linkage to the tin atom.

Lupin alkaloids 6. Stereochemistry of bis-quinolizidine alkaloids with γ-oxo-α,β-enamine system

1994 ◽  
Vol 72 (1) ◽  
pp. 193-199 ◽  
Author(s):  
Tadeusz Brukwicki ◽  
Waleria Wysocka ◽  
Barbara Nowak-Wydra
Keyword(s):  
Conformational Changes ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Coupling Constants ◽  
Hydroxyl Group ◽  
Coupling Constant ◽  
H Nmr ◽  
Time Signals ◽  
Low Sensitivity ◽  
First Time

1H nmr, 1H,1H and 1H,13C COSY, and 2D J-resolved spectra of multiflorine (1) and 13α-hydroxymultiflorine (2) in CDCl3 were taken. Some erroneously determined chemical shifts in 1 were corrected and for the first time signals in 2 were assigned. Most of the coupling constants in 1 and 2 were established. A coupling constant of H7–H17β and chemical shifts for H17β, C14, and C8 were used to define the conformational equilibrium of boat or chair forms in the C rings, in 1 and 2 in solution. The results obtained confirm the previous findings based on chemical shifts of C12: ca. 75 and 70% of the "boat" conformer in 1 and 2, respectively, at room temperature. Of all the criteria used, the H7–H17β coupling constant seems to be least sensitive to the influence of substituents at rings A and D. From the Haasnoot equation, torsion angles of HCCH in regions of molecular geometry featuring low sensitivity to conformational changes were calculated. The hydroxyl group at position 13α has a slight influence on the geometry of ring D.

Substituent effects on geminal proton–proton coupling constants

1970 ◽  
Vol 48 (13) ◽  
pp. 2134-2138 ◽  
Author(s):  
Y. L. Chow ◽  
S. Black ◽  
J. E. Blier ◽  
M. M. Tracey
Keyword(s):  
Carbon Tetrachloride ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Proton Proton ◽  
Proton Coupling ◽  
Geminal Proton ◽  
Geminal Coupling ◽  
Hammett Σ Constants

The geminal coupling constants between the non-equivalent benzylic protons of a series of para- and meta-substituted N-benzyl-2-methylpiperidines were shown to be proportional to the Hammett σ constants of the substituents with ρ −1.38 in carbon tetrachloride, −1.21 in benzene, and nearly 0 in 1 N DCl solutions. The ρ values were compared with those of other series and were discussed in terms of the possible conformations involved. The chemical shifts of the benzylic protons of the piperidine derivatives did not give a good correlation with the Hammett σ constants in these solvents.

Synthese und Multikern-NMR-Spektroskopie einiger vier-und fünfgliedriger Zinn—Stickstoff-Heterocyclen / Synthesis and Multinuclear NMR Spectroscopy of Some Four-and Five-Membered Tin —Nitrogen Heterocycles

1988 ◽  
Vol 43 (6) ◽  
pp. 707-714 ◽  
Author(s):  
Carin Stader ◽  
Bernd Wrackmeyer ◽  
Dieter Schlosser
Keyword(s):  
Nmr Spectroscopy ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Chemical Shifts ◽  
Nitrogen Heterocycles ◽  
Spiro Compounds ◽  
Coupling Constants ◽  
Ring Size ◽  
Multinuclear Nmr Spectroscopy ◽  
Cyclic Compounds

Tin-nitrogen heterocycles [1,3,2,4λ2-diazasila- (1), -λ4-stannetidines (2), spiro-compounds (3, 4), 1,3,2λ4,4λ4-diazadistannetidines (5), 1,3,4,5,2λ2-diazadisila- (6) and -λ4-stannolidines (7)] have been characterized by 13C, 15N, 29Si and 119Sn NMR spectroscopy [chemical shifts δX and coupling constants nJ(119Sn-X) (n = 1, 2, 3; X = 13C, 15N, 29Si, 119Sn]. The influence of the ring size becomes apparent in particular by comparison of the various coupling constants. In the compounds 1 and 6 the presence of a two-coordinate tin atom is reflected by the extremely low shielding of the 119Sn nuclei and also by the reduced shielding of the 29Si nucleus. The comparison with δ(29Si) data for corresponding non-cyclic compounds indicates that the latter effect may be traced to intra-annular interactions in 1 and 6 which involve the lone electron pair at the tin atom.

15N Nucelar Magnetic Resonance Study of Two-Coordinate Phosphorus Cations - Sign-Determination of Coupling Constants – Application of Two-Dimensional (2D) Heteronuclear Shift Correlations

1992 ◽  
Vol 47 (5) ◽  
pp. 662-667 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Jürgen Schiller
Keyword(s):  
Chemical Shifts ◽  
Double Resonance ◽  
Lone Pair ◽  
Coupling Constants ◽  
Phosphorus Compounds ◽  
Positive Sign ◽  
Nuclear Shielding ◽  
First Time ◽  
N Natural Abundance

Cyclic and non-cyclic bis(amino)phosphenium cations (1 to 4) together with their precursors (bis(amino)phosphorus chlorides 5 to 8) and some other bis(amino)phosphorus compounds (9 to 14) have been studied by 13C, 15N (natural abundance), 29Si and 31P NMR spectroscopy. 15N chemical shifts and coupling constants 1J(31P15N) of phosphenium cations have been determined for the first time. NMR data of 1 to 4 are compared with those of a bis(amino)carbene and various bis(amino)stannylenes. In the phosphenium cations 1 to 4 the 15N nuclear shielding is considerably reduced (ca. 70 to 100 ppm as compared with 5 to 14) and there is a crude linear relationship between δ15N and δ31P values. Changes in the δ15N values of 1 to 4 do not reflect P-N (pp)π interactions. A positive sign has been determined for the coupling constants 1J(31Ρ15Ν) [reduced coupling constants 1K(31P15N) < O] for the phosphenium cations and for all other P(III)-N compounds studied. This was achieved by applying various one- and twodimensional heteronuclear double resonance techniques. The experiments also gave signs of the coupling constants 2J(31PN13C), 2J(31PN29Si), 3J(31PNC13C), 3J(31PNSi13C), 4J(31PNCC1H) and 4J(31PNSiC1H). Negative contributions to 1K(31P15N), arising from the lone pair of electrons at phosphorus, are more noticeable in the case of the phosphenium cations.

Distannylchalkogenide: 119Sn-NMR-Untersuchungen und die Kristall- und Molekülstrukturen von Bis(tri-tert-butylstannyl)oxid und Bis(tribenzylstannyl)sulfid / Distannylchalcogenides: 119Sn NMR Studies and the Crystal and Molecular Structures of Bis(tri-tert-butylstannyl)oxide and Bis(tribenzylstannyl)sulfide

1987 ◽  
Vol 42 (4) ◽  
pp. 387-394 ◽  
Author(s):  
Susanna Kerschl ◽  
Bernd Wrackmeyer ◽  
Detlef Männig ◽  
Heinrich Nöth ◽  
Rudolf Staudigl
Keyword(s):  
Bond Angle ◽  
Linear Structure ◽  
Molecular Structures ◽  
Coupling Constants ◽  
X Ray Diffraction ◽  
Nmr Studies ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
119Sn Nmr ◽  
Geminal Coupling

Bis(triorganylstannyl)chalcogenides (O, S, Se) have been studied by 119Sn NMR in solution. In most cases the magnitude of the geminal coupling constants 2J(SnSn) are indicative of a bent arrangement SnXSn (X = O, S, Se). The exception is bis(tri-tert-butylstannyl)oxide for which the linear structure S n - O - S n as determined by X-ray diffraction in the solid state is preserved in solution. The trend of the coupling constants 2J(SnSn) depending on X and on the bond angle SnXSn suggests that 2J(SnOSn) > 0 and 2J(SnSSn), 2J(SnSeSn) <0. The X-ray diffraction study of bis(tribenzylstannyl)sulfide shows a bent arrangement (∢SnSSn 105.52(14)°) in contrast to the corresponding oxide.

Magnetic non-equivalence of fluorine atoms of a trifluoromethyl group

1982 ◽  
Vol 60 (19) ◽  
pp. 2451-2455 ◽  
Author(s):  
Mohsin A. Khan ◽  
Donald F. Tavares ◽  
Arvi Rauk
Keyword(s):  
Methoxy Group ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Trifluoromethyl Group ◽  
Single Bond ◽  
Hindered Rotation ◽  
Geminal Coupling ◽  
Coupling Pattern ◽  
Derivatives Of

The three fluorine atoms of N,N-dialkyl amide and chloride derivatives of 2-methoxy-2-phenyl-3,3,3-trifluoropropanoic acid are magnetically nonequivalent below –60 °C and exhibit a clear ABC coupling pattern from which chemical shifts and geminal coupling constants are readily derived. The chemical shifts span a range of about 10 ppm and the geminal coupling constants average about 110 Hz. A five bond coupling of about 5 Hz is observed between the hydrogens of the methoxy group and one of the nonequivalent fluorine atoms of the trifluoromethyl group. Barriers to the hindered rotation about the single bond to the trifluoromethyl group are in the range 36–46 kJ/mol.

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