Analysis of the effect of the electronic structure of the Cl atom in complexes of chlorides of group IV elements on Cl NQR frequency and asymmetry parameter

Analysis of changes in ³⁵Cl NQR frequency of complexes MCl₄.L and MCl₄.2L for M = Si, Ge, Sn and Ti was performed. The population of the atomic orbitals was calculated by the quantum chemistry methods PM3 and INDO. The results provided an explanation of the changes in ³⁵Cl NQR frequency and the asymmetry parameter upon complex formation. In the complexes of non-transition elements, a decrease in ³⁵C1 NQR frequency is first of all related to increasing population of p_z orbitals on Cl atoms. In the complexes of Ti, the increase in ³⁵Cl NQR frequency depends on a decrease in the p_π to d_π electron density transfer.     

A study of electronic structure of SbCl5.L and SnCl4.L2 complexes by the PM3 method

Electronic structures of SbCl₅.L and SnCl₄.L₂ complexes were studied by the semiempirical PM3 method. The results were compared with the data from ³⁵Cl NQR and ¹²¹Sb NQR studies and Mössbauer spectra.

A good correlation was obtained between the calculated and experimental values of quadrupole coupling constants. The calculated energies of the donor-acceptor bond formation were compared with the degree of electron density transfer. The derived correlation dependences between the above two parameters suggest different properties for cis and trans complexes.     

A study of electronic structure of SbCl5.L and SnCl4.L2 complexes by the PM3 method

Electronic structures of SbCl₅.L and SnCl₄.L₂ complexes were studied by the semiempirical PM3 method. The results were compared with the data from ³⁵Cl NQR and ¹²¹Sb NQR studies and Mössbauer spectra.

A good correlation was obtained between the calculated and experimental values of quadrupole coupling constants. The calculated energies of the donor-acceptor bond formation were compared with the degree of electron density transfer. The derived correlation dependences between the above two parameters suggest different properties for cis and trans complexes.     

Peculiarities of atomic interaction in organic molecules of 3- and 4-coordinated phosphorus using ab initio calculations and Cl NQR

The results of ab initio calculations at the MP2/6-31G(d) level of molecules of the series ClPXX′ (X, X′=C₂H₅, N(CH₃)₂, OCH₃) and ClP(M)XX′ (M=O, S; X=CH₃, ?CH₃; X′=C₂H₅, OCH₃) with total optimization of their geometry were presented. They were compared with the obtained earlier results of such calculations at the RHF/6-31G(d) level and with experimental ³⁵Cl nuclear quadrupole resonance (NQR) spectra for these compounds. MP2/6-31G(d) calculations confirm non-inductive influence of heteroatoms on the geminal Cl atom in the non-linear three-atomic Cl–P–M groups. They agree to the conclusion that the abnormal correlation of the ³⁵Cl NQR frequencies for the compounds studied at different X, X′ and M is caused, in general, by the P–Cl bond polarization under the action of the geminal atom partial charges directly through the field. The satisfactory conformity between the experimental ³⁵Cl NQR frequencies and those estimated from 3p-components of the Cl atom valence p-orbitals calculated at the MP2/6-31G(d) level was obtained.     

A Cl nuclear quadrupole resonance study of NH4ICl4·H2O

The “missing” fourth ³⁵Cl NQR frequency postulated for NH₄ICl₄H₂O at room temperature has been observed. Four signals were also found for this compound at 195K, but the results at 77K were less clear-cut, with either five or (probably) six resonances detected. The occurrence of a phase transition between 77 and 195K seems likely. A structure is suggested for the ICl₄⁻ ion at room temperature from the relationship found previously between NQR frequency and bond length in tetrachloroiodates.     

XVI. (2,5-C4Bu2RHN)MCl3 (M = Ti, Zr, Hf; R = H, SiMe3)—Azacyclopentadienyl-Komplexe der Gruppe 4-Metalle

The azacyclopentadienyl compounds (2,5-C₄^tBu₂RHN)MCl₃ (M = Ti, Zr, Hf; R = H, SiMe₃) have been prepared as stable solids from the lithiated pyrroles and MCl₄. The π-coordination of the azacyclopentadienyl ligands, as suggested from ¹³ C NMR data, has been confirmed for (2,5-C₄^tBu₂H₂N)TiCl₃ by an X-ray diffraction study.     

柄型金属有机化合物(Ⅳ)——四甲基二硅桥连取代环戊二烯基钛和锆化合物的合成及催化乙烯聚合

四甲基二硅桥连取代环戊二烯基配体相继与丁基锂及MCl₄·2THF作用,生成四甲基二硅桥连取代环戊二烯基钛和锆化合物(Me₂SiSiMe₂)(C₅H₄R)(C₅H₄R')MCl₂[R=H,R'=t-Bu,M=Ti(1),Zr(2),Hf(3);R=H,R'=Me,M=Ti(4);R=R'=Me,M=Ti(5),Zr(6)].通过元素分析、MS和¹HNMR谱表征了化合物的分子结构,并通过X射线衍射分析测定了化合物1的晶体结构.研究了在甲基铝氧烷(MAO)的助催化下,化合物1-3和6对乙烯聚合的催化性能。     

The electronic structure of diphenyltin(IV) dichloride, calculation of the mössbauer isomer shift and the quadrupole splitting of tin and the nuclear

Nonrelativistic and quasirelativistic SCF-MS calculations on the diphenyltin(IV) dichloride monomer and possible “dimer”, give theoretical insight into the intermolecular chlorine interaction. This molecule is not a polymer like other diorganotin(IV) dichlorides. A weak interaction occurs in the valence orbital electronic structure; the extent of the interaction is given by the molecular one-electron properties. The isomer shift and the quadrupole splitting of the Mössbauer active ¹¹⁹Sn, and the nuclear quadrupole resonance (n.q.r.) frequency of ³⁵Cl are properties which are helpful in analysing the extent of intermolecular interaction in the “dimer”. The calculated isomer shift and quadrupole splitting agree with experiment. The n.q.r. frequency of ³⁵Cl does not agree well with experiment, which is not a single crystal measurement, but nevertheless the weakness of the intermolecular chlorine interaction was confirmed. Further confirmation comes from the total density plot of (Ph₂SnCl₂)₂.     

双核茂金属催化剂的合成、表征与应用

使用桥连配体锂盐与MCl₄络合, 合成了4个不同结构的双核茂金属化合物[μ,μ-(CH₂)₃]{[C(H)·(η⁵-C₅H₄)(η⁵-C₁₃H₈)](MCl₂)}₂[M=Zr or Ti](4, 5)和[μ,μ-(CH₂)₃]{[C(H)(η⁵-C₅H₄)(η⁵-C₉H₆)]·(MCl₂)}₂[M=Zr or Ti](6, 7), 配体和化合物都经过核磁氢谱(¹H NMR)、 碳谱(¹³C NMR)、 红外光谱(IR)及元素分析等表征, 确认了化学结构. 以甲基铝氧烷(MAO)为助催化剂, 化合物4~7为催化剂催化丙烯聚合, 考察了聚合温度、 乙烯压力、 铝钛或铝锆比对催化剂活性及聚合物分子量的影响. 结果表明, 多亚甲基桥连双核茂金属是高活性乙烯和丙烯聚合催化剂, 乙烯聚合活性最高达到7.5× 10⁶ g PE/(mol Zr·h)(化合物6), 丙烯聚合活性达 10 × 10⁵ g sPP/(mol Zr·h)(化合物4). 所得间规聚丙烯(sPP)的间规度指数(SI, r) 达到90%. 在同样条件下, 双核化合物的催化活性、 聚合物分子量M_w(> 100000)以及分子量分布(MWD>2.5)均比相应的单核化合物高(M_w<70000, MWD≤2), 表明该体系中存在较强的核效应.     

Cl (Pj)_ fine structure quantum yields from UV dissociation of PCl3, CCl4, CHCl3 and Cl2 in a supersonic jet

Jet-cooled phosphorus trichloride, carbon tetrachloride, chloroform and molecular chlorine are photodissociated in the UV wavelength range 235–238 nm. Chlorine atom photofragments Cl (²P_3/2) and Cl* (²P_1/2) are detected via resonance-enhanced (2+1) ionization throughout the 232–238 nm wavelength region. The relative Cl* yields, φ*=[Cl*]/([Cl]+[Cl*]), are measured for both ³⁵Cl and ³⁷Cl isotopes using the two-photon atomic transitions at 235.3 nm for Cl and 237.8 nm for Cl*. Preliminary results indicate that the Cl* yields are different for the two isotopes for some of the precursors. In addition, we obtained the two-photon oscillator strength of the Cl transition at 237.7 nm relative to the Cl* transition at 237.8 nm. The advantage of using the two-photon Cl transition at 237.7 nm for quantum yield measurements is discussed.     

Matrixreaktion von AlCl mit HCl: IR-spektrum von HAlCl2

In an argon matrix AlCl can react with HCl by excitation of a low pressure mercury lamp to HAlCl₂. Isotopic splitting (H/D and ³⁵Cl/³⁷Cl) and force constant calculations show that the observed frequencies can be assigned to a planar molecule HAlCl₂. The bending mode δ (AlCl₂) could not be observed.     

Azo-containing phosphine complexes of palladium(II) and platinum(II) and their effectiveness in the Heck reaction: crystal and molecular structure of [PdCl2{PPh2{1-(4-MeC6H4N2)-2-OC(O)Me---C10H5}]·2EtOH

Reaction of Na[MCl₄] (M=Pd or Pd) with the azo-containing phosphines Ph₂P{1-(4-RC₆H₄N₂)-2-OR′-C₁₀H₅} {R=Me (I), NMe₂ (II); R′=C(O)Me} affords the complexes [MCl₂L₂] (1–4) in good yield. Complexes 1–4 have all been fully characterised by elemental analysis, ¹H-, ¹³C{¹H}-, and ³¹P{¹H}-NMR spectroscopy and UV–visible spectroscopy. The use of 1 in the Heck reaction has been investigated and shown to effect up to 1000 turnovers.     

NQR in tert-butyl chloride

Tert-butyl chloride has been broadly studied experimentally through various techniques such as X-ray crystallography, DTA, and NMR. It was also studied experimentally through nuclear quadrupole resonance (NQR), but this study was limited and incomplete. In this paper, we present a more detailed study of TBC through the NQR of ³⁵Cl. Our results show that near 120 K, the onset of the CH₃ groups semirotations around symmetry axis C₃ takes place with an activation energy U=16.1 kJ mol⁻¹. This intramolecular movement produces a T₁ minimum near 148 K and is the dominant mechanism of the nuclear spin-lattice relaxation in phase III of this compound. In phase II of TBC, we show that there are not only methyl groups semirotations, but also semirotations of the whole molecule around a different axis from the symmetry axis C′₃ (C–Cl bond) with an activation energy of E=10.4 kJ mol⁻¹.     

Matrixisolation von AsOCl und SbOClMatrix isolation of molecular AsOCl and SbOCl

The molecules AsOCl and SbOCl are formed by reactions of silver with mixtures of AsCl₃ and O₂ or SbCl₃ and O₂ respectively at about 1300 K. After condensation in an argon matrix at 15 K the two stretching vibrations of AsOCl can be observed in the IR spectrum: 984.4 cm⁻¹ [ν(AsO)] and 378.7 cm⁻¹ [ν(AsCl)]. This assignment is confirmed by the measured ¹⁶O/¹⁸O and ³⁵Cl/³⁷Cl isotopic shifts. The calculated AsO force constant shows that there is a real AsO double bond in this molecule.

We failed in the characterisation of SbOCl by the same method, because this molecule is only stable at 1350 K in the presence of gaseous Sb₄O₆ and therefore the absorptions of SbOCl are superimposed by the very strong bands of Sb₄O₆.     

Stabile Bis(η-alkin)MCl2-komplexe; Darstellung und reaktivität

The synthesis and reactivity of {(η⁵-C₅H₄SiMe₃)₂Ti(CCSiMe₃)₂} MCl₂ (M = Fe: 3a; M = Co: 3b; M = Ni: 3c) is described. The complexes 3 are accessible by the reaction of (η⁵-C₅H₄SiMe₃) ₂Ti(CSiMe₃)₂ (1) with equimolar amounts of MCl₂ (2) (M = Fe, Co, Ni). 3a reacts with the organic chelat ligands 2,2′-dipyridyl (dipy) (4a) or 1,10-phenanthroline (phen) (4b) in THF at 25°C to afford in quantitative yields (η⁵-C₅H₄SiMe₃)₂Ti(CSiMe₃)₂ (1) and [Fe(dipy)₂]Cl₂ (5a) or [Fe(phen)₂]Cl₂ (5b). 1/n[Cu^IHal]_n (6) or 1/n[Ag^IHal]_n (7) (Hal = Cl, Br) react with {(η⁵ -C₅H₄SiMe₃)₂Ti(CCSiMe₃)₂}FeCl₂ (3a), by replacement of the FeCl₂ building block in 3a, to yield the compounds {(η⁵-C₅H₄SiMe₃)₂Ti(C CSiMe₃)₂}Cu^IHal (8) or {(η⁵-C₅H₄SiMe₃)₂Ti(CSiMe₃)₂}Ag^IHal (9) (Hal = Cl, Br), respectively. In 8 and 9 each of the two Me₃SiCC-units is η²-coordinated to monomeric Cu^I Hal or Ag^IHal moieties. Compounds 8 and 9 can also be synthesized by the reaction of (η⁵-C₅H₄SiMe₃)₂ Ti(CSiMe₃)₂ (1) with 1/n[Cu^IHal]_n (6) or 1/n [Ag^IHal]_n (7) in excellent yields. All new compounds have been characterized by analytical and spectroscopic data (IR, ¹H-NMR, MS). The magnetic moments of compounds 3 were measured.     

Spectres de rotation de la molécule de chlorobenzéne : I. Variétés isotopiques monosubstituées et structure rs

The microwave spectra of chlorobenzene “(1)-³⁵Cl”, all eight mono-[“(1)-³⁷Cl”, “(1)-³⁵Cl, (2)D”, “(1)-³⁵Cl, (3)D”, “(1)-³⁵Cl, (4)D”, “(1)-³⁵Cl, (1)-¹³C”, “(1)-³⁵Cl, (2)-¹³C”, “(1)-³⁵Cl, (3)-¹³C”, “(1)-³⁵Cl, (4)-¹³C”], one di[“(1)-³⁵Cl, (2,6)D₂,”] and one trisubstituted species [“(1)-³⁷Cl, (2,6)D₂”] have been investigated. From the moments of inertia of the vibrational ground state the r_s structure was derived. The reliability of the two small a coordinates could be enhanced through use of the multiply substituted species. The errors of the moments of inertia were propagated to the structural parameters. It could be shown that the benzene ring is deformed. However the quantitative deformation could not be established due to the rather large errors of some structural parameters.     

Alkylaminophosphanyl substituted half-sandwich complexes of vanadium(III) and chromium(III): preparation and reactivity in ethylene polymerisation

[Cp^R(RPNEt₂)]M (Cp^R=t-BuC₅H₃, C₅(CH₃)₄, indenyl, fluorenyl; M=Li, K) smoothly react with VCl₃(Me₃P)₂ and CrCl₃(THF)₃ systems giving paramagnetic complexes [Cp^R(R¹PNEt₂)]MCl₂ (M=V(Me₃P)₂, Cr). After reaction with MAO these complexes are active in the polymerisation of ethylene yielding highly crystalline, high-density products of high molecular weight (M_w ranging from 100 000 to 4.5×10⁶ g mol⁻¹, 20≤T_p≤100 °C). Polymerisation with chromium complexes leads to the formation of polyethylenes with broad molecular weight distribution.     

Preparation and characterization of ruthenium(II), rhodium(III) and iridium(III) complexes of isocyanide bearing the azo group

Reactions of [(η⁶-arene)RuCl₂]₂ (1) (η⁶-arene=p-cymene (1a), 1,3,5-Me₃C₆H₃ (1b), 1,2,3-Me₃C₆H₃ (1c) 1,2,3,4-Me₄C₆H₂(1d), 1,2,3,5-Me₄C₆H₂ (1e) and C₆Me₆ (1f)) or [Cp*MCl₂]₂ (M=Rh (2), Ir (3); Cp*=C₅Me₅) with 4-isocyanoazobenzene (RNC) and 4,4′-diisocyanoazobenzene (CN–R–NC) gave mononuclear and dinuclear complexes, [(η⁶-arene)Ru(CNC₆H₄N=NC₆H₅)Cl₂] (4a–f), [Cp*M(CNC₆H₄N=NC₆H₅)Cl₂] (5: M=Rh; 6: M=Ir)_, [{(η⁶-arene)RuCl₂}₂{μ-CNC₆H₄N=NC₆H₄NC}] (8a–f) and [(Cp*MCl₂)₂(μ-CNC₆H₄N=NC₆H₄NC)}] (9: M=Rh; 10: M=Ir)_, respectively. It was confirmed by X-ray analyses of 4a and 5 that these complexes have trans-forms for the ---N=N--- moieties. Reaction of [Cp*Rh(dppf)(MeCN)](PF₆)₂ (dppf=1,1′-bis (diphenylphosphino)ferrocene) with 4-isocyanoazobenzene gave [Cp*Rh(dppf)(CNC₆H₄N=NC₆H₅)](PF₆)₂ (7), confirmed by X-ray analysis. Complex 8b reacted with Ag(CF₃SO₃), giving a rectangular tetranuclear complex 11b, [{(η⁶-1,3,5-Me₃C₆H₃)Ru(μ-Cl}₄(μ-CNC₆H₄N=NC₆H₄NC)₂](CF₃SO₃)₄ bridged by four Cl atoms and two μ-diisocyanoazobenzene ligands. Photochemical reactions of the ruthenium complexes (4 and 8) led to the decomposition of the complexes, whereas those of 5, 7, 9 and 10 underwent a trans-to-cis isomerization. In the electrochemical reactions the reductive waves about −1.50 V for 4 and −1.44 V for 8 are due to the reduction of azo group, [---N=N---]→[---N=N---]²⁻. The irreversible oxidative waves at ca. 0.87 V for the 4 and at ca. 0.85 V for 8 came from the oxidation of Ru(II)→Ru(III).     

Determination of chemical shift parameters from zeeman nuclear quadrupole resonance in single crystals

The components of the chemical shift tensor of the ³⁵Cl nuclei in paradichlorobenzene single crystal have been determined directly from Zeeman-split NQR spectra, with the magnetic field applied parallel to the principal axes of the electric-field-gradient tensor. The results are compared with values obtained by NMR in the pure quadrupole regime.     

The sign of the spin-orbit coupling constant in (t2) t2 states of mx4 ions

It is shown that the sign of the spin-orbit coupling constant in ²T₂ states of MX⁺₄ molecular ions (M = C, Si, Ge; X = F, Cl, Br, I) arising from the (t₂)⁵ electron configuration can be positive, negative or even zero. Predominantly, the sign depends on the orientation of the p-orbitals on the four halogen atoms with respect to the M-X bonds. Experimentally observed splittings show that it is incorrect to describe the two highest t2 valence orbitals of MX₄ as pure pπ non-bonding and pure pσ bonding, since both exhibit pσ/pπ mixing. This is confirmed by semi-empirical SCF MNDO molecular-orbital calculations.