2-Amino-4-aryl-1-arylideneaminoimidazoles and Acylation Products: A Multinuclear (<Superscript>1</Superscript>H, <Superscript>13</Superscript>C, <Superscript>15</Superscript>N) NMR Study

Summary. The structure of 2-amino-4-aryl-1-arylideneaminoimidazoles in DMSO-d₆ solution was investigated by means of NMR spectroscopic methods (¹H, ¹³C, ¹⁵N). From these data the (E)-configuration at the excocyclic C=N bond and a strong preference for the conformer with the imidazole H-5 and the N=CH proton being spatially close (s-trans regarding the N–N bond) can be concluded. Reaction of the title compounds with acetic anhydride leads to mono and diacylation at the 2-amino group, whereas treatment with pivalic anhydride exclusively affords the corresponding monoacyl product. The mono- and diacylation products exhibit similar configurational and conformational properties as the parent compounds.     

Trioxaphosphocanes-1,3,6,2, etude par R.M.N. (13C, 1H, 31P et stereochimie

The stereochemistry of several 2-R-1,3,6,2-trioxaphosphocanes (R = Cl, OCH₃, CH₃, N(CH₃)₃ has been investigated by ¹H, ¹³C and ³¹P n m r spectroscopy.     

Structure and intramolecular mobility of N-(thio)phosphoryl(thio)amides: XV. Study of structure and intramolecular dynamics of N3-phenyl-N1-(diisopropoxythiophosphoryl)thiosemicarbazide in CD2Cl2 solution by 1H, 13C and 31P NMR spectroscopy

Structure and intramolecular transformations of N³-phenyl-N¹-(diisopropoxythiophosphoryl)-thiosemicarbazide in CD₂Cl₂ were studied by one- and two-dimensional ¹H, ¹³C and ³¹P NMR spectroscopy. The combined analysis of the data of NMR spectroscopy and calculation simulation confirmed a high lability of the studied compounds resulting in the formation of various conformational and tautomeric forms in solutions. The preference of Z,E-conformation of the amide form with cis- and trans-location of two N-H groups and the C=S group relatively to the two C-N bonds was revealed.     

Spiroborates derived from catecholborane and ephedrine type aminoalcohols - model compounds for the study of intramolecular N→B coordination by dynamic 1H-, 11B- and 13C-NMR.

A convenient synthesis of the title compounds is reported. These serve as models to study intramolecular N→B coordination by means of dynamic NMR spectroscopy (¹H, ¹¹B, ¹³C). Steric interactions between substituents at the boroxazolidine ring (C(5)Ph, C(4)Me, NMe) determine the stability of the N→B bond and the nitrogen configuration.     

Vibrational spectra and structural features of carbene analogs ElII(OCH2CH2NMe2)2 and ClElIIOCH2CH2NMe2 (ElII = Ge, Sn, Pb)

Vibrational spectra of compounds of divalent Group 14 elements El^II(OCH₂CH₂NMe₂)₂ with El^II = Ge (1), Sn (2), Pb (3) and ClEl^IIOCH₂CH₂NMe₂ with El^II = Ge (4) and Sn (5) were measured for the first time and analyzed within the framework of DFT calclations. Monomeric compounds 1 and 2 whose molecules are stabilized only through intramolecular coordination were confirmed to be isostructural. Unlike 1 and 2, plumbylene 3 is a polymer in both solution and the crystalline state; the latter was confirmed by X-ray diffraction analysis. The ν^s _C-N stretching frequency in the CH₂NMe₂ fragment was shown to decrease by 80–100 cm⁻¹ owing to the formation of the coordination bond El←N. To elucidate the mechanism of a dynamic flip-flop process suggested earlier based on the broadening of some signals in the NMR spectra of compounds 1 and 4, the Raman spectra of solutions of compounds 1 and 2 in THF and Py were obtained. These experiments revealed no equilibrium with participation of a stable form with one coordination bond El←N cleaved along with the starting molecule. This is consistent with the results of the corresponding quantum chemical calculations of thermo-dynamic parameters. A somewhat different, more probable mechanism of the dynamic process was proposed, which involves an overturn of the CH₂NMe₂ fragment with cleavage of the El←N bond in the transition state only.     

1H NMR spectra of 1-alkyl-1,2,3,4-tetrahydro-2-oxo-3-azocine-carboxylic acid derivatives and their analogues

¹H NMR spectra of 1-alkyl-1,2,3,4-tetrahydro-2-oxo-3-azocinecarboxylates and -carbonitriles indicated that the geminal protons at the 1-α-position were located in noneqnivalent magnetic environments. The difference in the chemical shifts amounted to as much as 0.73 ppm in the case of methyl 1-ethyl-1,2,3,4-tetrahydro-2-oxo-3-azocinecarboxylate at 26°, and the free energy of activation for the coalescence was estimated to be larger than 23 $\text{kcal}\text{mol}$. The same type of nonequivalence and coalescence phenomena were also observed even with dimethyl protons at the 1-γ-position of 1-isobutyl-1,2,3,4-tetrahydro-2-oxo-3-azocinecarboxylate (ΔG^≠_c = 19 $\text{kcal}\text{mol}$). The situation was hardly affected by the reduction of the CC double bonds. The nonequivalence was not observed, however, if the substituent at the 3-position was absent. Therefore, these novel ¹H NMR spectra of 1-alkyl protons in the title compounds were concluded to be due to strong coupling between the restricted rotation around N(1)—C(α) bond and inversion of the 2-oxoazocine ring which required high energy of activation.     

Substituent Effects on 13C NMR and 1H NMR Chemical Shifts of CH=N in Multi-substituted Benzylideneanilines

Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs (abbreviated XBAYs) were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the ¹H NMR chemical shifts (^δH(CH=N)) and ¹³C NMR chemical shifts (^δC(CH=N)) of the CH=N bridging group from di-substituted to multi-substituted XBAYs was made based on a total of 182 samples of XBAYs, together with the NMR data of other 129 samples of di-substituted XBAYs quoted from literatures. The results show that the substituent specific cross-interaction effect parameter \begin{document} $\left(\Delta\left(\displaystyle\sum\sigma\right)^2\right)$ \end{document} plays an important role in quantifying the ^δC(CH=N) values of XBAYs, but it is negligible for quantifying the ^δH(CH=N) values; the other substituent parameters also present different influences on the ^δC(CH=N) and ^δH(CH=N). On the whole, the contributions of X and Y to the ^δC(CH=N) of XBAYs are balanced, but the ^δH(CH=N) values of XBAYs mainly rely on the contributions of X.     

NMR study (1H, 13C and 29Si) of the methylallylsilanes

¹H, ¹³C and ²⁹Si NMR data for the compounds (CH₃)_xSi(CH₂CHCH₂)_4-x are reported. The ¹H resonances from the π system are indicative of the electron-supplying inductive effect (+I) of the (CH₃SiCH₂, moiety but the corresponding ¹³C_π chemical shifts seem to be influenced by a sterically induced polarization of the C-H bonds. The ¹³C_All, ¹³C_Me and ²⁹Si chemical shift data reveal an important neighbour anisotropy contribution originating from the π system. Ultraviolet study of the compounds mentioned above gives indication of a σ—π conjugation in accordance with PES and ab initio results [1—5]. The trend observed in the various coupling constants is too small to be Interpreted.     

13C- und 199Sn-NMR untersuchungen an alkinylstannanen

Chemical shifts δ(¹³C), δ(¹¹⁹Sn) and coupling constants J(¹¹⁹Sn¹³C) for alkynylstannanes of the type R_4-nSn(CCR′)_n (n = 1–4) are reported. The values of ¹J(¹¹⁹Sn¹³C) and ²J(¹¹⁹SnC¹³C) depend upon the nature of the substituent R′. ¹J(¹¹⁹Sn¹³C) in Sn(CCCH₃)₄ is 1168 Hz, much larger than a value predicted in the literature of ca. 700 Hz. The comparison of δ(¹¹⁹Sn) for (CH₃)₂Sn(CCR′)₂ and 1,1,4,4-tetramethyl-1-stannacyclohexadi-2,5-ene suggests that the δ(¹¹⁹Sn) of alkynylstannanes are determined only to a small extent by the diamagnetic anisotropic effect of the CC-triple bond.     

The 1,3B 1— 1A 1 systems of the nitrite anion in a NaHCO 2 host crystal

The lower energy electronic transitions of the NO ^?₂ anion in a NaHCO ₂ host crystal at 4 K are reported and analyzea. The ¹B ₁— ¹A ₁ system, whose origin is at 25 649 cm ^?1, is seen in absorption and fluorescence accompanied by a long progression in the symmetric bending mode (ν′ ₂ = 626, ν″ = 820 cm ^?1). The implied change in the ONO bond angle is 9 ± 3 ⁰. The ³B ₁ → ¹A ₁ phosphorescence is quite weak with an extrapolated origin at 18 059 cm ^?1. The ¹B ₁ ← ¹A ₁ absorption linewidths, the lower-resolution fluorescence photoexcitation spectrum, and the relative phosphorescence and fluorescence intensities suggest the involvement of an intermediate state in populating the triplet manifold after excitation of the ¹B ₁ state.     

Sorption and desorption of 125I-, 137Cs+, 85Sr2+ and 152,154Eu3+ on disturbed soils under dynamic flow and static batch conditions

Sorption of radionuclides on homogenized soils (under 2.5 mm grain size) from synthetic groundwater of 8·10⁻³M ionic strength and pH 8.5 has been studied under dynamic (flow) and static (batch) conditions. The corresponding water-soluble compounds, as carriers in the 10⁻⁶ mol/dm³ concentration, were added into the SGW prior to the experiments. Soil samples were taken from several locations around the environment of the High Level Waste Storage Facility at Nuclear Research Institute Řež plc in 5–100 cm depth. The dynamic experiments were carried out in columns made of PP+PE injection syringes of 17.8 cm length and 2.1 cm in diameter. A multi-head peristaltic pump was used for pumping the water upward through the columns at a seepage velocity of about 0.06 cm/min in average. The radioactive nuclides were added into the water stream individually in a form of a short pulse in 0.1 cm³ of demineralized water. Dynamic desorption experiments were performed with the same experimental arrangement using a mixture of 10⁻²N H₂SO₄ and 10⁻²N HNO₃ in a volume ratio of 2: 1. Retardation, distribution and hydrodynamic dispersion coefficients during transport of radionuclides were determined by the evaluation of the integral form of a simple advection-dispersion equation, used for fitting experimental data and modeling the theoretical sorption breakthrough and desorption displacement curves. The static experiments were realized in 100 cm³ plastic bottles stirring 5 g of soil samples with SGW occasionally in a soil to SGW ratio of 1: 10 (m/V). Kinetic parameters including equilibrium sorption activity, activity transfer rate constants and sorption half-times were also determined. The results of dynamic experiments were compared with static sorption experiments.     

Migratory-insertion reactions involving the thiocarbonyl ligand. dihapto-thioacyl complexes from the rearrangement of arylthiocarbonyl complexes of osmium(II). Structure of Os(η2-CSR)(η1-O2CCF3)(CO)(PPh3)2

Reaction of HgR₂ with OsHCl(CS)(PPh₃)₃ yields red, five-coordinate, OsRCl-(CS)(PPh₃)₂ (R = p-tolyl). From this have been derived the compounds OsRX(CS)(PPh₃)₂ with X = Br, I, S₂CNEt₂, O₂CMe, O₂CCF₃. These compounds add an additional ligand, MeCN, CO or CNR to form colourless, six coordinate arylthiocarbonyl complexes, which undergo migratory-insertion reactions to form red, dihapto-thioacyl complexes. The crystal structure of a representative example, Os(η²-CSR)(η¹-O₂CCF₃)(CO)PPh₃)₂ has been determined. The red equant crystals are orthorhombic, space group P2₁2₁2₁, a 11.584(1), b 19.184(2), c 18.90(1) Å, V 4199 ų, Z  4. The structure was solved by conventional heavy-atom methods and refined by full-matrix least-squares employing anisotropic thermal parameters for all non-hydrogen atoms except the carbon atoms of the triphenylphosphines. The final R factor is 0.057 for 2868 observed reflections.The coordination geometry in the monomeric complex is that of an octahedron distorted by the constraints of the ligands. The triphenyl phosphine ligands are mutually trans; the equatorial plane contains carbonyl, monohapto-trifluoroacetate, and dihapto-thioacyl ligands. Bond distances and angles are OsP 2.405, 2.407(4) Å; POsP 173.9(1)°; OsCO 1.83(2) Å; Os-O (trifluoroacetate) 2.206(11) Å; OsC (thioacyl) 1.91(2); OsS 2.513(6); CS 1.72 Å. The CS bond length implies a reduction in bond order from 2.0 to approx. 1.5 upon coordination to the metal.The η²-thioacyl ligand in Os(η²-CSR)Cl(CNR)(PPh³)₂ is methylated with methyl triflate and further reaction with LiCl produces the thiocarbene complex OsCl₂(C[SMe]R)(CNR)(PPh₃)₂.     

29Si and 13C NMR spectra of permethylpolysilanes

²⁹Si, ¹³C and ¹H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe₂)_nMe where n = 1 to 6, for the cyclic permethylpolysilanes (Me₂Si)_n where n = 5 to 8, and for a few related compounds. For linear polysilanes the ²⁹Si and ¹³C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the ²⁹Si and ¹³C resonances, whereas more remote silicon atoms lead to downfield shifts. The ²⁹Si chemical shifts of the polysilane chains are linearly related to the ¹³C shifts of the carbon atoms attached to the silicon. The ²⁹Si and ¹³C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled ²⁹Si NMR spectra are reported for Me₃SiSiMe₃ and for (Me₂Si)_n, n = 5 to 7.     

NMR investigation of bis(2,3-alkanedione dioximato)-bis(pyridine)cobalt(III) iodide complexes: 1H and 13C NMR spectra and 13C spin-lattice relaxation time measurements

The complexes of trans-[Co(III)(R,CH₃-dioxH)₂(py)₂]I2 (R = CH₃, C₂H₅, n-C₃H₇ and n-C₄H₉) were investigated in solution by ¹H and ¹³C NMR spectra and ¹³C spin-lattice relaxation time measurements. The ¹H and ¹³C-resonances of the R = C₂H₅, n-C₃H₇ and n-C₄H₉) groups were shifted to higher field than those of the free ligands by the complexation; it was attributable to the ring current shielding due to the axial pyridine ligands of the complexes. ¹³C spin-lattice relaxation times were interpreted as due to movement of the axial pyridine ligands as if they twist around the CoN (pyridine nitrogen) bond axis and the above R groups were moving segmentally. These segmental movements allowed the R groups to approach closely toward the axial pyridine ring plane to experience the ring current shielding.     

Synthesis and 1H, 13C and 15N NMR characterisation of substituted Pyrazolo[4,3-c]quinolines and related compounds

A wide range of novel and known alkyl substituted pyrazolo[4,3-c]quinolines and related compounds were synthesized. Some of these compounds can undergo tautomerism and differences have been noted in the structural assignments already published. For each of these compounds, a complete assignment was made using ¹H, ¹³C and ¹⁵N one- and two-dimensional NMR measurements, including NOESY, COSY, ¹H-¹³C HSQC and ¹H-¹³C HMBC. ¹H-¹⁵N HMBC NMR has proved crucial in determining the relevant tautomeric and protonated state of the compounds.     

Some diels—alder reactions of η1-bonded cyclopentadienylmetal compounds

Bis(cyclopentadienyl)mercury readily undergoes Diels—Alder reactions with RCCR (R = CO₂Me or CF₃), CF₃CFCFCF₃, CF₃CFCF₂, (CF₃)₂CC(CN)₂, C₂(CN)₄ and Ph$\text{NCONNC}$O to give stable adducts characterised by¹H, ¹⁹F and ¹³C NMR, spectroscopy. Similar reactions of CF₃CCCF₃ and CF₃CFCFCF₃ with the cyclopentadiene derivatives Me₃MC₅H₅ and (Me₃M)₂C₅H₄ (M = Si, Sn) are also described.     

13C-19F couplings and 19F NMR shifts of cycloalkyl,bicycloalkyl and steroid monofluoro compounds1

The stereospecifity of ¹³C-¹⁹F couplings is investigated with 20 alicyclic compounds. One bond couplings, ranging from 168 to 214 Hz, can be represented as a function of the corresponding ¹³C-H coupling constants. For comparison ¹³C-¹H couplings are determined for norboraane and adamantane and indicate considerable s character at the bridgehead C-H bond of the latter compound. One bond and geminal couplings (ranging from 18 to 24 Hz) are found to depend not significantly on the steric environment. With vicinal couplings a strong dependence is established on torsional angles, which is fitted to a Karplus function. Typical values for CCCF trans arrangements are around 10 Hz, for gauche angles less than 1.5 Hz. Vicinal couplings are substantially altered by electronegative substituents and by hybridization changes of participating carbon atoms. The ³J values observed with cycloalkylfluorides are interpreted on the basis of model geometries for the corresponding hydrocarbons. The influence of solvent and temperature changes is restricted to one bond couplings. ¹⁹F shifts in cyclohexane derivatives are constantly at higher field for axial fluorine (by ~20 ppm), but otherwise there is no significant relation to the orientation of neighbouring bonds, nor to ¹³C shifts of the Cα-F carbon atoms or to the corresponding one bond couplings.     

π‐Excess Aromatic σ2P Ligands: Formation of a Heterocyclic 1,2‐Diphosphine by the Addition of tBuLi and Subsequent Inverse Addition of the Product at the P=C Bonds of Two Molecules of 1‐Neopentyl‐1,3‐benzazaphosphole

The reactivity of tBuLi (pentane) toward the N‐neopentyl‐substituted π‐excess P=CH–N heterocycle 1 depends on the solvent (tetrahydrofuran, diethyl ether, hexane, and toluene) and reaction conditions. Trapping of the resulting organolithium compounds with CO₂/ClSiMe₃, ClSiMe₃, or EtI led to various products indicating CH lithiation ( 1a , b ), normal addition of tBuLi at the P=C bond (E/Z ‐2a , b ), inverse addition of the primary addition product 2_Li at the P=C bond of a second molecule 1 , affording 3‐tert‐butyl‐2,2’‐bis(1,3‐benzazaphospholines) 3 , or inverse addition of tBuLi ( 4b,c ). The formation of 3 demonstrates a novel route to asymmetric heterocyclic 1,2‐diphosphine ligands. The structure elucidation of the new compounds is based on their ³¹P and ¹³C NMR data with conclusive chemical shifts and P–C coupling constants, that of the isolated PH‐functionalized diphosphine 3 on crystal structure analysis.     

The application of 13C and 1H NMR spectroscopy to the investigation of the dinitrogen fixation process in the system (η-C5H5)2TiCl2-Mg

The N₂ reduction reaction in the system (η-C₅H₅)₂TiCl₂-Mg in tetrahydrofuran was examined. The ¹³C and ¹H NMR results as well as the chemical properties of the products formed revealed that the reaction yielded a mixture of compounds in which the titanium atom was bonded both to the μ-(η⁵: η⁵-fulvalene) ligand and to the cyclopentadienyl ligands. In this system dinitrogen undergoes reduction to N^3?, which then forms M₃N bridges (M = Ti, Mg). The nitride nitrogen may readily be oxidized to imide nitride N^?1, which may react further, e.g. with carbon monoxide to produce isocyanates, or, with excess oxidizing agent N₂. THF in this system undergoes polymerisation. In addition, a ?OC₄H₉ alkoxy group is formed which makes the substitution of the cyclopentadienyl group bonded to the titanium atoms possible.     

Spectres de vibration des molecules BCl2CO et BX2NCS (X = Cl,Br, I), champs de forces et modes normaux

Experimental data on the vibrational spectra of BX₂¹⁴NCS (X = Cl, Br or I), BCl₂¹⁵NCS, BBr₂¹⁵NCS, and BCl₂NCO are reported. Analysis of the results shows that the boron atom is bonded to the nitrogen atom, and the BN, CN, CS and CO bonds are colinear. Force fields are calculated and found to reproduce the experimental frequencies and the ¹⁰B-¹¹B and ₁₄N-₁₅N isotopic effects. High values are obtained for the force constant of the B-N stretching vibration (about 6.5 mdyn Å^?1) and it is shown that, owing to electron transfer from nitrogen to boron, the B-N bond is intermediate between a single and a double bond. The force constant νBX is marginally greater than that for the corresponding BX₂SH compounds. The C-N bond is weaker than in the NCS ion, whereas the CS bond is stronger.Calculation of the normal modes and the potential energy distribution shows that for the BCl₂NCO molecule, the B, N, C, and O atoms are almost equally involved in all the modes of A, symmetry, especially those at 2270, 1525 and 1022 cm^?1. On the other hand, for BX₂NCS compounds, the potential energy is relatively localised on one coordinate. Consequently, the group vibration approximation is justified in this case.