J(77Se,1H) and J(77Se,13C) couplings of seleno‐carbohydrates obtained by 77Se satellite 1D 13C spectroscopy and 77Se selective HR‐HMBC spectroscopy

Seleno‐carbohydrates are those in which the oxygen of the glycosidic bond or the hydroxyl group is artificially replaced with selenium. This substitution changes ¹H and ¹³C chemical shifts and produces spin coupling constants involving ⁷⁷Se. Coupling constants, such as ^2‐3J(⁷⁷Se, ¹H), are likely to be useful for conformational analyses of glycans because such couplings are never observed in natural glycans. Several papers have discussed the relationship between ^2‐3J(⁷⁷Se, ¹H) and conformation; however, only few reports describe ^1‐3J(⁷⁷Se, ¹³C), which could also be useful. Here, we obtain ⁷⁷Se coupling constants of seleno‐carbohydrates from ⁷⁷Se‐selective HR‐HMBC and ⁷⁷Se satellites in 1D ¹³C spectra and examine their conformations using the Newman projection scheme.     

Full four‐component relativistic calculations of the one‐bond 77Se–13C spin‐spin coupling constants in the series of selenium heterocycles and their parent open‐chain selenides

Four‐component relativistic calculations of ⁷⁷Se–¹³C spin–spin coupling constants have been performed in the series of selenium heterocycles and their parent open‐chain selenides. It has been found that relativistic effects play an essential role in the selenium–carbon coupling mechanism and could result in a contribution of as much as 15–25% of the total values of the one‐bond selenium–carbon spin‐spin coupling constants. In the overall contribution of the relativistic effects to the total values of ¹J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spin‐orbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic second‐order polarization propagator approach (CC2) with the four‐component relativistic density functional theory scheme is recommended as a versatile tool for the calculation of ¹J(Se,C). Solvent effects in the values of ¹J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.2–78.4) are next to negligible decreasing negative ¹J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of ⁷⁷Se–¹³C spin‐spin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.1–0.2‐Hz loss of accuracy. Copyright © 2014 John Wiley & Sons, Ltd.     

Die metall-kohlenstoff-bindung in carben- und carbin-komplexen. aussagen der 183W13C-kopplungen

The nuclear spin coupling constants¹J(¹⁸³W¹³C) and in some cases ²J(¹⁸³W¹³C) and ³J(¹⁸³W¹³C) are determined for 10 tungsten carbene and 9 tungsten carbyne complexes. ¹J is of analytical importance, being characteristically greater for WC than for WC bonds. This is due to different hybridisation at the carbon atom, and provides information about bond angles and polarities of WC and WCR units.Substituents R and R' in (CO)₅WCRR' and X(CO)₄WCR as well as the halogens X lead to minor changes in ¹J. These changes are comparable to those of ¹J(¹³C¹H) in correspondingly substituted methanes. Unexpectedly ¹J in_ creases with X = Cl, Br, I. ²J(¹⁸³W¹³C) though being much smaller than ¹J reflects different hydridisation at the β carbon atom.     

1H, 13C and 77Se NMR spectra of substituted selenoanisoles

The ¹H, ¹³C and ⁷⁷Se chemical shifts and the ¹J[C(Me)H(Me)], ^1.2J(SeC) and ²J(SeH) coupling constants in 14 para- or meta-substituted selenoanisoles, R? C₆H₄? Se? CH₃, have been measured and the dependence of these parameters on the electronic effects of the substituent R is discussed. A significant (up to 6 ppm) deviation from additivity of the substituent influence on the shielding of the ¹³C ring carbons has been found.     

Structure of sulfur-stabilized carbanions. A 13C NMR study of some α-lithio-sulfoxides and sulfones

¹³C chemical shifts and ¹J(¹³CH) coupling constants provide information on the structures of some α-lithio-sulfoxides and sulfones.     

Open‐chain unsaturated selanyl sulfides: stereochemical structure and stereochemical behavior of their 77Se–1H spin–spin coupling constants

Stereochemical structure of nine Z‐2‐(vinylsulfanyl)ethenylselanyl organyl sulfides has been investigated by means of experimental measurements and second‐order polarization propagator approach calculations of their ¹H–¹H, ¹³C–¹H, and ⁷⁷Se–¹H spin–spin coupling constants together with a theoretical conformational analysis performed at the MP2/6‐311G** level. All nine compounds were shown to adopt the preferable skewed s‐cis conformation of their terminal vinylsulfanyl group, whereas the favorable rotational conformations with respect to the internal rotations around the C–S and C–Se bonds of the internal ethenyl group are both skewed s‐trans. Stereochemical trends of ⁷⁷Se–¹H spin–spin coupling constants originating in the geometry of their coupling pathways and the selenium lone pair effect were rationalized in terms of the natural J‐coupling analysis within the framework of the natural bond orbital approach. Copyright © 2012 John Wiley & Sons, Ltd.     

A proton and carbon-13 nuclear magnetic resonance study of neopentylmercury compounds

Substituent effects on ¹⁹⁹Hg¹H and ¹⁹⁹Hg¹³C spinspin coupling constants have been studied for neopentylmercury derivatives, (CH₃)₃CCH₂HgR(or X), where R is covalently bonded Me, Et, t-Bu, neopentyl, and vinyl, and X is easily ionizable CN, Br, Cl, OCOCH₃, and ONO₂. Linear relationships exist between the methylene J(¹³CH) and ²J(HgH), ⁴J(HgC) and ²J(HgC) and ³J(HgC); but deviations from linearity occur for the chloride, bromide, acetate, and nitrate in the relationships between ²J(HgH) and ⁴J(HgH), ²J(HGH) and ²J(HGC). These deviations are discussed in terms of hyperconjugative p_πd_π bonding between the methylene CH bonds and mercury.     

Pulsed fourier transform NMR of substituted aryltrimethyltin derivatives : IV. Proton and carbon-13 NMR data for ortho-, 2,6-, and poly-substituted aryltrimethyltins

Proton and carbon-13 NMR data recorded in the Fourier transform mode are reported for ten ortho-substituted, six 2,6-disubstituted, and six miscellaneous polysubstituted aryltrimethyltin compounds. Although ¦¹J(¹³C¹H)¦ and ¦²J(¹¹⁹SnC¹H)¦ coupling constants are rather insensitive to substituent variation, tin methyl proton chemical shifts reflect the increasing inductive effects as methyl-, chloro-, fluoro-, and trifluoromethyl-groups are brought into juxtaposition with the trimethyltin moiety. Resonances in the natural-abundance carbon-13 NMR spectra for the tin derivatives are assigned on the basis of additivity relationships, proton undecoupled spectra, and relative magnitudes of ¦J(¹¹⁹Sn¹³C)¦ and ¦J(¹³C¹⁹F)¦ coupling constants. Mutually deshielding γ-, δ-, and ?-effects in the carbon-13 chemical shifts of substituent carbons are rationalized in terms of steric crowding between the trimethyltin group and neighboring substituents. Deshieldings in ring carbons formally para- to conjugating substituents are discussed in terms of the steric inhibition of resonance model. Previous conclusions concerning lack of significant higher coordination at tin in aryltin derivatives bearing substituents with lone pair electrons are corroborated in this work.     

Aromatic lead(IV) compounds : VIII. 13C FT-NMR spectroscopy of compounds Arn Pb(CH3)4−n (n = 0–4)

¹³C chemical shifts and ²⁰⁷Pb¹³C coupling constants are reported for some arylmethyllead compounds. The value of J(²⁰⁷Pb¹³C) is shown to depend on the number and the nature of the aryl groups.     

Deuterium-isotopieeffekte auf die 13C-chemischen verschiebungen und kohlenstoff-deuterium kopplungskonstanten in deuterierten verbindungen

The isotope effects on the ¹³C NMR chemical shifts and coupling constants (¹³C¹H and ¹³C¹H) have been determined by pulse Fourier transform ¹³C NMR investigation at 22·63 MHz for more than 30 common deuterated and protonated solvents. The observed isotope effects correlate with hybridization and electron withdrawal at the coupling carbon within the series of comparable compounds. In agreement with MO-theoretical calculations a linear correlation between the J_CD values of CD_x groups and the J_CH values of the corresponding CH_x groups was found. The experimentally determined J_CD values show an average deviation from the calculated line J_CD = (γ_D/γ_H)J_CH = 0·154 ×J_CH on the order of± 1 Hz.     

A 13C, 15N and 77Se NMR Study of Some Diseleno Sulfonamides

¹³C, ¹⁵N and ⁷⁷Se NMR data are reported for ten title compounds. Some linear correlations of selenium, nitrogen and carbon chemical shifts values are described. A number of one- and two- bond ⁷⁷Se-¹³C coupling constants values are also given.     

Carbon-13 fourier transform NMR studies of organotin compounds : III. Carbon-13 chemical shifts and tin-119—carbon-13 spin—spin coupling constants in acyclic,monocyclic and bicyclic organostannanes

Carbon-13 NMR parameters for 33 organotin compounds with a variety of structurul features were investigated in order to obtain information about the relationship between their structure and ¹³C NMR parameters. It was found that the substitution of a proton by a trialkyltin group generally produces an upfield shift for the directly bonded carbon. The γ-nuclei usually resonate at lower fields except where there is appreciable steric strain while the β-carbons undergo relatively constant shifts of approximately 3.5 to 4.5 ppm to lower fields. The magnitude of direct bond coupling Jz-sfnc;¹J(¹¹⁹Sn¹³C)z-sfnc; is influenced by the hybridization of the tin and the directly attached carbon atoms. In rigid organitins, the vicinal coupling constants show a Karplus type variation. In aliphatic organotins, the values of the vicinal¹¹⁹Sn¹³C coupling indicates a flexible molecular framework with a clear cut preference for certain conformations.     

Pulsed fourier transform NMR of substituted aryltrimethyltin derivatives : III. Proton data at 100 MHz and the derived Hammett σ-constant of the trimethyltin group

Proton NMR data at 100 MHz are reported for thirteen para- and meta-substituted phenyltrimethyltin compounds, XC₆H₄Sn(CH₃)₃, where X = para-N(CH₃)₂, para-OCH₃, para-OC₂H₅, para-CH₃, meta-CH₃, -H, para-F, meta-OCH₃, para-Cl, para-Br, meta-F, meta-Cl and para-Sn(CH₃)₃. Correlation coefficients with Hammett σ-constants of greater than 0.95 are obtained with the methyltin proton chemical shifts and coupling constants to carbon [¹J(¹³C¹H)] and tin [²J(SnC¹H)]. Solvent effects and other extraneous factors invalidate comparisons of ? values in terms of the relative attenuation of the transmission of substituent effects through homologous carbon, silicon, germanium and tin systems, but coupling constant data reflect a diminution of ca. one tenthfold per bond in the order ?[C(1)Sn] > ? [SnC] > ? [CH]. Satisfactory correlations (r > 0.95) are obtained in this series of closely-related compounds among the conventionally recorded two-bond, ²J(SnC¹H) and the constituent, one-bond ¹J (Sn¹³C) and J(¹³C¹H) coupling constants, but the correlation coefficient for the comparison between the two one-bond couplings, ¹J(Sn¹³C) and ¹J(¹³C¹H) is lower (r = 0.872). Changes in the couplings at the methyltin carbon bond tin-119 atoms are interpreted in terms of isovalent hybridization; a model based upon effective nuclear charges is tested with respect to both NMR coupling constants and ¹¹⁹Sn Mössbauer Isomer shifts at tin and is invalidated. Proton and carbon-13 NMR, chemical shift and coupling constant data are used to derive a Hammett σ-constant for the para-trimethyltin group of ?0.14, and the significance of this value is discussed.     

Long-range nuclear spin-spin coupling between 11B and 13C, 29Si or 119Sn: a promising tool for structural assignment

The influence of unresolved long-range nuclear spin-spin coupling [ⁿJ(¹¹BX) (n > 1; X = ¹³C, ²⁹Si or ¹¹⁹Sn)] on X resonances has been studied for aminoboranes (1 and 2), haloboration (2 and 4), hydroboration (5) and organoboration products of alkynes (6 and 7). The differential broadening of X resonances in the X NMR spectra arising from ⁿJ(¹¹BX) (most obvious for X= ¹¹⁹Sn) shows a qualitatively useful pattern of various coupling pathways. |²J(¹³CN-¹¹B)| in 1 and 2 appears to be sensitive to the nature of the trans-ligand and to the ring rize. In many alkenylboranes (3, 4, 5b and d, 6 and 7) the magnitude of the coupling constants across the CC double bond follows the trend |²J(¹¹BX)| ∼ |³J(¹¹BX)|_cis < |³J(¹¹BX)|_trans. An increasing number of electropositive substituents at the CC double bond causes an increase in the magnitude of |³J(¹¹BX)|_cis,trans. If there are only organyl groups of hydrogen attached to the CC double bond, as in the hydroboration products of alkynes (5a and c) |ⁿJ(¹³C-¹¹B)| appears to be too small with respect to [T_Q(¹¹B)]⁻¹, and the differential broadening was neglibible under the experimental conditions used.     

Temperature dependences of J(C,H) and J(C,D) in 13CH4 and some of its deuterated isotopomers

The nuclear spin—spin coupling constants J(C,H) and J(C,D) have been measured over the temperature range 200–370 K for the methane isotopomers ¹³CH₄, ¹³CH₃D, ¹³CHD₃ and ¹³CD₄. The coupling constants increase with increasing temperature for any one isotopomer and decrease with increasing secondary deuterium substitution at any one temperature. The results are entirely attributable to intramolecular effects and the data have been fitted by a weighted least-squares regression analysis to a spin—spin coupling surface thereby yielding a value for ¹J_e(C,H), the coupling constant at equilibrium geometry, and values for the bond length derivatives of the coupling. We find that ¹J_e(C,H) = 120.78 (±0.05) Hz which is about 4.5 Hz smaller than the observed value in ¹³CH₄ gas at room temperature. Results are also reported for J(H,D) in ¹³CH₃D and ¹³CHD₃ for which no temperature dependence was detected.     

13C, 15N and 29Si nuclear magnetic resonance studies of some aminosilanes and aminodisilanes

¹³C, ¹⁵N (at natural abundance) and ²⁹Si NMR data (chemical shifts and coupling constants) are reported for aminosilanes R₂R′SiNHR¹ (1), bis(silyl)amines Me₂R′SiNHSiMe₃ (2), 1,2-bis(amino)-ethanes (3), bis(amino)silanes RR′Si(NHR¹)₂ (4), 1,2-bis(amino)tetramethyldisilanes (5) and 1,1,2,2-tetrakis(amino)dimethyldisilanes (6). The δ¹⁵N values depend more on the nature of the substituents R¹(H, alkyl, aryl) at the nitrogen atom (in the same way as for other amines) than on different substituents at the silicon atom. A linear correlation between ¹J(²⁹Si¹⁵N) and ¹J(²⁹Si¹³C) is proposed for silanes in which the SiN unit is replaced by the SiCH unit. This correlation comprises all ¹J(²⁹Si¹⁵N) values for aminosilanes R_4-nSi(N)n (n = 1–4) and—most likely—also for aminodisilanes, and it predicts ¹J(²⁹Si¹⁵N)>0 if the corresponding value |¹J(²⁹Si¹³C)|>25 Hz. For the first time a two-bond coupling across Si, ²J(²⁹Si ¹⁵N) = 6.9 Hz, has been observed for 6a. In the case of 6b (R¹ = ^sBu) all resonances for the diastereomers are resolved in the ¹⁵N and ²⁹Si NMR spectra in contrast to the ¹H and ¹³C NMR spectra.     

σ,π-conjugation and 199Hg shielding constants in benzyl derivatives of mercury

The ¹⁹⁹Hg chemical shifts in a number of benzylmercuric chlorides containing methyl substituents in various positions of the benzene nucleus are studied by the heteronuclear ¹H-{¹⁹⁹Hg} double resonance technique. Meta- and para-methyl substituents are shown to have no pronounced action on the shielding whereas ortho-methyl groups each shift the signal by 30 ppm downfield. The observed effect is due to an increase in the population of conformers with the CHg bond lying out of the aromatic cycle plane. The departure from planarity favours conjugation between the electrons of the CHg bond and the π-electronic system of the ring. The J(¹H¹⁹⁹Hg) and J(¹³C¹⁹⁹Hg) coupling constant values obtained in this work confirm the latter conclusion.     

Carbon-13 n.m.r. of the 8-phosphabicyclo[3.2.1]octane system

¹³C Chemical shifts and ¹³C? ³¹P nuclear spin coupling constants have been determined for 26 8-phosphabicyclo[3.2.1]octane derivatives, namely phosphines, phosphine oxides, phosphine sulphides and one phosphonium salt. The influence of the phosphorus configuration on δ and ²J(PC) values was examined and other factors influencing the ²J(PC) coupling constant are discussed.     

13C nuclear magnetic resonance spectra of arylthallium(III) bis(trifluoroacetates)

¹³C chemical shifts and ¹³C? ²⁰⁵Tl spin–spin coupling constants are reported for phenylthallium(III) bis(trifluoroacetate) and some of its mono- and dimethyl derivatives. The signs of ⁿJ(¹³C, ²⁰⁵Tl) relative to ⁿ⁺¹J(¹H, ²⁰⁵Tl) are determined by offresonance decoupling of protons.     

NMR studies of bridged ring systems: XIX—13C?1H spin coupling and 13C chemical shift of the bridge methylene in benzonorbornene and benzonorbornadiene

Data on ¹³C chemical shifts and ¹³C? ¹H spin coupling constants of norbornane ( 1 ), norbornene ( 2 ), norbornadiene ( 3 ), benzonorbornene ( 4 ) and benzonorbornadiene ( 6 ) are reported. The non-equivalence in J(¹³C? H) values determined from the two bridge methylene proton signals in 2,2,3,3-tetradeuteriobenzonorbornene ( 5 ) and 6 is briefly discussed. The extraordinary deshielding of the bridge methylene carbon in 6 has been noted.