Nuclear Quadrupole Resonance and Stereochemistry I. α – Chloro ethers

³⁵Cl nuclear quadrupole resonance spectra of cyclic α-chloro ethers of known configuration are presented. The resonance frequencies of chlorine atoms in equatorial positions are in every case some 2.5 MHz higher than those of corresponding chlorine atoms in axial positions. Similar results are obtained for open-chain trichloromethyl ethers and the effect is sufficiently well-defined to distinguish between configurational isomers and establish their conformation. These results may be rationalised in terms of a model in which the lone-pair electrons on the oxygen atom hyperconjugate with the electrons of the C? Cl bond.     

Quantum chemical calculations and35Cl NQR study of the molecular structure of trichloroacetyl halides and trichloroacetaldehyde

An optimal geometry of CCl₃C(O) X molecules (X=H, F, Cl, Br, and I) is determined by the MNDO quantum chemical method. According to the results of calculations, the molecules in the free state have an eclipsed conformation with a syn-peri-planar position of the oxygen atom and one of the chlorine atoms of the trichloromethyl group. However, as follows from the³⁵Cl NQR spectra at different temperatures, in the crystal state of CCl₃C(O)X this conformation is distorted under the influence of intermolecular interactions due to the torsional rotation of the CCl₃ group around the C-C bond. Indicatory potentialities of the NQR method with respect to the structural features that are due to crystallographic effects are discussed. Perm State University. Translated fromZhurnal Strukturmoi Khimii, Vol. 37, No. 3, pp. 494–500, May-June, 1996.     

Specific Interactions and the Nature of the Chemical Nonequivalence of Chlorine Atoms in the ECl<Subscript>3</Subscript> Group (E = C,P) of Trichlorophosphonium Ylides and Isomeric Dichloro(trichloromethyl)phosphine

The nature of the asymmetry of the ECl₃ group (E = C, P) in dichloro(trichloromethyl)phosphine and trichlorophosphonium methylide and dichloromethylide was studied by nonempirical and MNDO-PM3 calculations and ³⁵Cl NQR spectroscopy. The chemical nonequivalence of chlorine atoms in the CCl₃ group of dichloro(trichloromethyl)phosphine is caused by steric interaction with the PCl₂ fragment. In the PCl₃ group of trichlorophosphonium methylide and dichloromethylide, this nonequivalence arises from specific interactions with the lone electron pair of the ylide carbon atom, whose p-character is about 94% on the RHF/6–311⁺⁺G(3df,3pd) level. The alteration of the type of interaction predicts inversion of the ³⁵Cl NQR signals of the PCl₃ group in trichlorophosphonium ylide and dichloromethylide in relation to those of the CCl₃ group in the experimental spectrum of dichloro(trichloromethyl)phosphine. The MNDO-PM3 method characterizes dichloro- and diphenylmethylides as unstabilized structurally stable ylides.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1148–1153.Original Russian Text Copyright © 2005 by Romanenko.     

35Cl NQR spectra, structure, and mutual influence of substituents in the series of chlorine-containing organic compounds of pentavalent phosphorus

Regularities of transmission of the effect of equatorial and axial substituents were established for a number of chlorine-containing organic compounds of pentatalent phosphorus using³⁵Cl NQR spectra. The field constants of³⁵Cl NQR frequencies of the chlorine atoms participating in the P−Cl bond were estimated for a series of tetrahedral phosphorus ions. The³⁵Cl NQR frequencies of chlorine atoms in tetracoordinated ions of pentavalent phosphorus and in analogous isoelectronic silicon compounds are related by a linear dependence. Deceased Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 915–922, May, 1999.     

29Si and 13C NMR spectra of chloro- and fluoro-substituted linear permethylpolysilanes

²⁹Si and ¹³C NMR spectra are reported for the three halopolysilane series Me(SiMe₂)_nCl, Cl(SiMe₂)_nCl and F(SiMe₂)_nF, where n = 2 to 6. Except for the dihalodisilanes (XSiMe₂)₂, data for all of the compounds fit linear relationships based on substituent constants for chlorine or fluorine atoms in the α, β and γ positions. The effects of halogen substitution on ²⁹Si and ¹³C chemical shifts are rapidly attenuated along the polysilane chain, becoming negligible four atoms away from the halogen. The NMR data provide no evidence for long-range electronic transmission from chlorine or fluorine in halopermethylpolysilanes of the type suggested by other workers [1].     

Recoil chlorine reactions with ethylene

The reactions of recoil³⁸Cl atoms produced through the³⁷Cl(n,)³⁸Cl process in the CF₃Cl–C₂H₄ gas phase are described in this work. The CF₃Cl is a chlorine source as well as moderator. Scavengers, such as O₂ and H₂S, were added to the system to discriminate the reactions induced by energetic and/or thermal chlorine atoms. The radioactive³⁸Cl-labeled products were separated using gas-chromatogarphic technique followed by an external proportional counter for quantitative determination of the product yeids. The mechanisms of the chemical reactions are predicted to account for the formation of these organic compounds.     

Stabilization of H3 + in the high pressure crystalline structure of HnCl (n = 2–7)

The particle-swarm optimization method has been used to predict the stable high pressure structures up to 300 GPa of hydrogen-rich group 17 chlorine (H_nCl, n = 2–7) compounds. In comparison to the group 1 and 2 hydrides, the structural modification associated with increasing pressure and hydrogen concentration is much less dramatic. The polymeric HCl chains already present in the low temperature phase under ambient pressure persist in all the high pressure structures. No transfer of electrons from the chlorine atoms into the interstitial sites is found. This indicates the chemical bonding at high pressure in group 17 elements is fundamentally different from the alkali and alkaline elements. It is found that almost perfectly triangular H₃ ⁺ ions can be stabilized in the crystalline structure of H₅Cl.     

Substituent chemical shifts of the organotin moiety in compounds of the type RSnMenCl3 − n (n = 0 to 3; R = n-alkyl)

The ¹³C and ¹¹⁹Sn NMR spectra of 33 organotin compounds of the type RSnMe_nCl_{3 ? n} and related types are discussed. The substituent effects of the groups SnMe₃, SnMe₂Cl, SnMeCl₂ and SnCl₃ (and of some related groups) on the carbon chemical shifts in the alkyl group R have been determined; the SnMe₃ group causes a small upfield shift of the carbon attached to it, while the other groups cause downfield shifts. The shifts show a monotonic change on replacing methyl groups in Me₃Sn by chlorine atoms. The effects on carbons further removed from the tin atom are discussed. Variation in R causes little change in ⁿJ(Sn? C) or δ(¹¹⁹Sn).     

A study of the transfer of the electronic influence of substituents in o-carboranes by nuclear quadrupole resonance

The ³⁵Cl NQR spectra of 2-substituted 1-chloromethyl-o-carboranes and of 1-chloromethyl-9,12-dihalogeno-o-carboranes have been investigated. The anomalous influence of two halogen atoms present in positions 9 and 12 of the carborane nucleus on the electron density of the chlorine atom in the CH₂Cl group is explained by the combined action of their –I and +M effects, and also by the effect of p d conjugation. The comparatively high ³⁵Cl NQR frequency for o-ClCH₂CB₁₀H₁₀CH is due to the large –I effect of the carboranyl group. The induction constants of a number of groups attached to the carborane ring have been evaluated. In the molecules of the 2-substituted 1-chloromethyl-o-carboranes spatial interaction between X and Cl clearly appears. The substituents X in compounds of this series can be divided into three types according to their electronic influence: 1) electron-donating substituents, 2) substituents containing a mobile hydrogen atom (capable of forming a hydrogen bond), and 3) substituents possessing an unshared pair of electrons capable of passing into the vacant 3d orbital of a chlorine atom.     

35Cl, 93Nb, 181Ta,and 121Sb NQR in Cl5MV · OPCl3 (MV = Nb,Ta, Sb,or P) Complexes

The behavior of ³⁵Cl NQR spectra in Cl₅M · OPCl₃ complexes is affected by the nature of the metal center and the distortion of its surrounding geometry. In all cases considered, the ³⁵Cl NQR frequencies in the OPCl₃ fragment shift toward higher frequencies upon complex formation, whereas the frequencies of axial chlorine atoms in the Cl₅M group in the phosphorus and antimony complexes lie below those for the equatorial atoms, and in the niobium and tantalum complexes, the frequencies of the axial atoms are higher than those of the equatorial ones.     

Chlorido[N,N′‐dibenzyl‐N′′‐(trichloroacetyl)phosphoramidato‐κ2O,O′](1,10‐phenanthroline‐κ2N,N′)copper(II)

In the title complex, [Cu(C₁₆H₁₆Cl₃N₃O₂P)Cl(C₁₂H₈N₂)], the Cu^II cation presents a square‐pyramidal environment, where the CuO₂N₂ base is formed by two O atoms from carbonyl and phosphoryl groups, and by two N atoms from a 1,10‐phenanthroline molecule. A coordinated Cl atom occupies the apex. N—H...Cl hydrogen bonds link the molecules into one‐dimensional chains. The trichloromethyl group is rotationally disordered over two positions, with occupancies of 0.747 (7) and 0.253 (7).     

Crystal structure of the dichlorobis(1-allyltetrazole-N4)copper(II) complex [Cu(1-CH2=CHCH2−N4CH)2Cl4/2]∞∞

The crystal structure of the dichlorobis(1-allyltetrazole-N⁴)copper(II) complex was determined by X-ray diffraction analysis. The crystals are monoclinic, a=14.233(3), b=6.755(1), c=7.273(1) Å, β=104.63(3)°, V_cell=676.6(2), ų, space group P2₁/c, Z=4, d_calc=1.741g/cm³, d_msd=1.69 g/cm³, CAD-4, λMoK_α radiation, R_F=0.0377 for 520 F_hkl>4σ(F_hkl) and 0.0560 for all 872 independent reflections. The structure is layered; the coordination polyhedron of copper is a square bipyramid, in which the equatorial positions are occupied by two chlorine atoms (Cu?Cl 2.27(2)–2.31(2) Å) and two N⁴ atoms of planar tetrazole ligands, whereas the axial positions are occupied by two chlorine atoms of the neighboring molecules of the complex (Cu?Cl 2.97(2)–3.01(2) Å). The sublattice of chlorine atoms is disordered in such a way that the [CuCl_4/2]_∞∞ layer is a superposition of two variants with weights 61(3) and 39(3)% and with similar geometrical characteristics: the equatorial chlorine atoms in variant A are replaced by the axial atoms in variant B and vice versa. The tetrazole ligand has the same position in both variants. In general, the crystal is a polytype with random alternation of A and B type blocks. It is shown that the compound is isostructural to the complex with 1-ethyltetrazole [Cu(ettz)₂Cl₂], in which only variant B is realized.     

Synthesis and x-ray crystal structure of the TiMgCl5(OOCCH2Cl) · (ClCH2COOC2H5)3 Adduct

The synthesis of the TiMgCl₅(OOCCH₂Cl) · (ClCH₂COOC₂H₅)₃ adduct, obtained by reacting TiCl₄ with a solution of MgCl₂ in dry ClCH₂COOC₂H₅, is reported together with its molecular and crystal structure as determined by x-ray diffraction. The structure was solved by direct and Fourier methods and refined by least-squares techniques to R = 0.057 for 1318 independent observed reflections. Crystals are monoclinic, space-group P2₁/c, with 4 formula units in a unit-cell of dimensions a = 10.480(4), b = 19.641(9), c = 16.597(6) Å, β = 120.21(5)°. The titanium(IV) atom is octahedrally coordinated by five chlorine atoms and an oxygen atom of a OOCCH₂Cl residue. The magnesium atom is similarly coordinated by two chlorine atoms, the carbonyl oxygen atoms of three ClCH₂COOC₂H₅ molecules and an oxygen atom of the OOCCH₂Cl residue. The two octahedra share an edge by a double chlorine bridge between the magnesium and the titanium atoms and are also connected by the COO group of the OOCCH₂Cl residue. Changes in the configurations and dimensions with respect to the free acceptor and donor molecules are discussed.     

The Mass Spectral Studies of Halogenated Vinyl Methanesulfonates

The mass spectra of saturated sulfonate esters^1,2) have been reported recently. No study has been made on the vinylic methanesulfonates. In order to understand their breakdown patterns, several chloro- and fluoro-containing vinyl methanesulfonates have been made³⁾ and their mass spectra studied. The chlorine compounds are chosen because the natural abundance of isotope ³⁵Cl and ³⁷Cl can serve as a internal tag. The vinyl methanesulfonates containing electronegative fluorine are used as a comparison to the chloro-compounds because of their similar electronegativities.     

Crystal structure determination of complexes of monomethylammonium chloride and mercury(II) chloride: CH3NH3HgCl3, (CH3NH3)2HgCl4, and CH3NH3Hg2Cl5

The crystal structures have been determined of CH₃NH₃HgCl₃, (CH₃NH₃)₂HgCl₄, and CH₃NH₃Hg₂Cl₅. In (CH₃NH₃)₂HgCl₄ the Hg^II atom is tetrahedrally coordinated by four Cl atoms with Hg? Cl bond lengths of 2.464 to 2.478 Å. In the other two compounds the Hg^II atom is involved in two short covalent Hg? Cl bonds, forming a pseudo HgCl₂ molecule and two much longer bridging Hg? Cl bonds. The methylammonium groups are connected by hydrogen bonds to the chlorine atoms. The nature of the hydrogen bonding scheme probably causes disorder of the methylammonium groups.     

Atmospheric reactions of chloroethenes with the OH radical

The kinetics and products of the homogeneous gas-phase reactions of the OH radical with the chloroethenes were investigated at 298 ± 2 K and atmospheric pressure. Using a relative rate technique and ethane as a scavenger for the chlorine atoms produced in these OH radical reactions, rate constants (in units of 10^?12 cm³ molecule^?1s^?1) of 8.11 ± 0.24, 2.38 ± 0.14, and 1.80 ± 0.03 were obtained for 1,1-dichloroethene, cis-1, 2-dichloroethene and trans-1,2-dichloroethene, respectively. Under these conditions, the major products observed by long pathlength FT-IR absorption spectroscopy were HCHO and HC(O)Cl from vinyl chloride; HC(O)Cl from cis- and trans-1,2-dichloroethene; HCHO and COCl₂ from 1,1-dichloroethene; HC(O)Cl and COCl₂ from trichloroethene; and COCl₂ from tetrachloroethene. In the absence of a Cl atom scavenger, significant yields of the chloroacetyl chlorides, CH_xCl_3?xC(O)Cl, were observed from 1,1-dichloro-, trichloro- and tetrachloroethene, indicating that these products resulted from reactions involving chlorine atoms. The yields of all of these products are reported and the mechanisms of these gas-phase reactions discussed. In addition, OH radical reaction rate constants were redetermined, in the presence of a Cl atom scavenger, for cis- and trans-1,3-dichloropropene and 3-chloro-2-chloromethyl-1-propene, being (in units of 10^?12 cm³ molecule^?1 s^?1) 8.45 ± 0.41, 14.4 ± 0.8, and 33.5 ± 3.0, respectively.     

Assessment of the intramolecular C–H⋯X (X=F,Cl, Br) hydrogen bonding of 1,4-diphenyl-1,2,3-triazoles

The intramolecular six-membered C–H?X (X=F, Cl, Br) hydrogen bonding motif of halogen-substituted 1,4-diphenyl-1,2,3-triazole compounds has been assessed. Twelve triazole derivatives have been designed and prepared, which bear fluorine, chlorine or bromine atoms on the ortho- and/or para-positions of the benzene rings. ¹H NMR, X-ray crystallography, and DFT calculation investigations revealed that the ortho-fluorine, chlorine, and bromine atoms of the benzene ring on the C-4 of the triazole unit all can form six-membered C–H?X hydrogen bonding. In contrast, only fluorine forms similar, relatively stable intramolecular hydrogen bonding on the N-1 side of the triazole unit.     

High-field solid-state <Superscript>35</Superscript>Cl NMR in selenium(IV) and tellurium(IV) hexachlorides

We report solid-state ³⁵Cl NMR spectra in three hexachlorides, (NH₄)₂SeCl₆, (NH₄)₂TeCl₆ and Rb₂TeCl₆. The C_Q(³⁵Cl) quadrupole coupling constants in the three compounds were found to be 41.4±0.1 MHz, 30.3±0.1 MHz and 30.3±0.1 MHz, respectively, some of the largest C_Q(³⁵Cl) quadrupole coupling constants ever measured in polycrystalline powdered solids directly via ³⁵Cl NMR spectroscopy. The ³⁵Cl EFG tensors are axial in all three cases reflecting the C_4v point group symmetry of the chlorine sites. ³⁵Cl NMR experiments in these compounds were only made possible by employing the WURST-QCPMG pulse sequence in the ultrahigh magnetic field of 21.1 T. ³⁵Cl NMR results agree with the earlier reported ³⁵Cl NQR values and with the complementary plane-wave DFT calculations. The origin of the very large C_Q(³⁵Cl) quadrupole coupling constants in these and other main-group chlorides lies in the covalent-type chlorine bonding. The ionic bonding in the ionic chlorides results in significantly reduced C_Q(³⁵Cl) values as illustrated with triphenyltellurium chloride Ph₃TeCl. The high sensitivity of ³⁵Cl NMR to the chlorine coordination environment is demonstrated using tetrachlorohydroxotellurate hydrate K[TeCl₄(OH)]?0.5H₂O as an example. ¹²⁵Te MAS NMR experiments were performed for tellurium compounds to support ³⁵Cl NMR findings.     

Theoretical investigation of the halogen bonded complexes between carbonyl bases and molecular chlorine

The halogen bonded complexes between six carbonyl bases and molecular chlorine are investigated theoretically. The interaction energies calculated at the CCSD(T)/aug‐cc‐pVTZ level range between ?1.61 and ?3.50 kcal mol^?1. These energies are related to the ionization potential, proton affinity, and also to the most negative values (V_s,min) on the electrostatic potential surface of the carbonyl bases. A symmetry adapted perturbation theory decomposition of the energies has been performed. The interaction results in an elongation of the Cl? Cl bond and a contraction of the CF and CH bonds accompanied by a blue shift of the ν(CH) vibrations. The properties of the Cl₂ molecules are discussed as a function of the σ*(Cl? Cl) occupation, the hybridization, and the occupation of the Rydberg orbitals of the two chlorine atoms. Our calculations predict a large enhancement of the infrared and Raman intensities of the ν(Cl? Cl) vibration on going from isolated to complexed Cl₂. © 2015 Wiley Periodicals, Inc.     

Reactions of trichloromethyl radicals with organosilicon compounds

The photolysis of carbon tetrachloride in the presence of a number of organosilicon compounds has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the organosilane. Arrhenius parameters for hydrogen atom transfer were determined relative to those for trichloromethyl radical combination. The activation energies for the reaction of methyl, trifluoromethyl, and trichloromethyl radicals with organosilicon compounds are compared and the results rationalized in terms of polar effects.