Test study on the excitation spectra of the N<Subscript>2</Subscript>–He van der Waals molecule

We have performed ab initio fourth-order Møller–Plesset perturbation theory calculations in the framework of the supermolecule approach on the vertical excitation spectra of the weakly bound van der Waals N₂–He dimer. They indicate a ``T-shaped' stablest ground N<sub>2</sub>(X<sup>1</sup><sub>g</sub><sup>+</sup>)–He(<sup>1</sup>S) electronic state with a well depth, D<sub>e</sub>, of 21.63 cm<sup>–1</sup> at a minimum distance, R<sub>e</sub>, of 3.44 Å and zero-point vibration correction, D<sub>o</sub>, of 7.07 cm<sup>–1</sup>. They also indicate a ``T-shaped' stablest excited conformer with R_e=3.25 Å, D_e=36.85 cm^–1 and D_o=17.06 cm^–1 for the N₂(B³_g)–He(¹S) triplet electronic level. In order to investigate the use of less-demanding correlation methods, test density functional theory calculations using the mPW1PW exchange–correlation functional are also presented for comparison.     

Theoretical studies on CuF+, CuF,CuF−, CuF2, and CuF2 −

Ab initio SCF studies were performed with Cu and F basis sets of near-Hartree-Fock (HF) limit quality to obtain accurate SCF results for the molecular ground state properties of CuF⁺, CuF, CuF^–, CuF₂, and CuF₂ ^–, as well as for the first two low-lying excited states of CuF₂. A study on the effects of electron correlation was carried out by Møller-Plesset (MP) and configuration interaction (Cl) calculations. The effect of relativity on the⁶³Cu nuclear quadrupole coupling in CuF was determined by use of a coupled HF procedure for a first-order spin-orbital-averaged Pauli operator. At the HF level the⁶³Cu coupling constant was found to be 35.8 MHz (in e²qQ h^–1), while allowing for relativity the value was reduced to 29.1 MHz, which is in better agreement with the experimental value of 22.0 MHz. The calculated molecular properties for CuF [r _e = 1.737 Å,D _e=4.38 eV, _e = 562 cm^–1 (MP4);r _e= 1.796 Å,D _e = 3.91 eV, _e=585 cm^–1 (CISD)] were in good agreement with experiment (r _e = 1.745 Å,D _e = 4.43 eV, _e=623 cm^–1). The adiabatic ground-state potential curve of CuF⁺ avoids crossing near the equilibrium distance between the two ionic potential curves Cu⁺-F and Cu²⁺-F^–. At the crossing point the Cu and F electric field gradients show a sharp discontinuity.     

Spectroscopic investigations on AsH(XΣ) radical using CCSD(T) theory in combination with correlation-consistent quintuple basis set

The equilibrium internuclear separations, harmonic frequencies and potential energy curves of the AsH(X³Σ⁻) radical have been calculated using the coupled-cluster singles–doubles–approximate-triples [CCSD(T)] theory in combination with the series of correlation-consistent basis sets in the valence range. The potential energy curves are all fitted to the Murrell–Sorbie function, which are used to reproduce the spectroscopic parameters such as D_e, ω_eχ_e, α_e, B_e and D₀. The present D₀, D_e, R_e, ω_e, ω_eχ_e, α_e and B_e obtained at the cc-pV5Z basis set are of 2.8004 eV, 2.9351 eV, 0.15137 nm, 2194.341 cm⁻¹, 43.1235 cm⁻¹, 0.2031 cm⁻¹ and 7.3980 cm⁻¹, respectively, which almost perfectly conform to the measurements. With the potential obtained at the UCCSD(T)/cc-pV5Z level of theory, a total of 18 vibrational states is predicted when the rotational quantum number J is set to equal zero (J = 0) by numerically solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined when J = 0 for the first time, which are in excellent agreement with the experiments.     

Application of open-shell coupled cluster theory to the ground state of GaAs

Summary Theoretical calculations at the coupled cluster level of theory including all single, double and perturbative triple excitations, CCSD(T), are carried out for the^3– ground state of GaAs. Employing a (7s5p3d1f) basis set, the theoretical predictions forr _e (2.560 Å), _e (217 cm^–1),D _e (1.84 eV), and IP (7.80 eV), are in good agreement with recent experimental results. The importance of includingf-type polarization functions in the basis set and the effect of correlating 3d electrons are discussed in detail.     

Study of a hollow cathode arc discharge in the presence of chromium oxide

A hollow cathode arc discharge in hydrogen has been used for the purpose of chromium oxide reduction, the solid oxide being placed inside the anode. Mass transport from the oxide to the gas phase and excitation conditions in the plasma have been investigated. The results show that a substantial amount of oxide is transferred to the gas phase with subsequent reduction and deposition inside the cathode cavity, in the form of a pure metal. The residual part condenses on the discharge chamber wall as an amorphous substance, containing 50–60% of Cr metal, and on the anode surface under the form of a mixture of chromium oxide and metal crystals (10%). From spectroscopic investigations it follows that, inside the anode zone, total Cr concentration in the gas phase is of the order of 10¹⁴ cm^–3, the excitation temperature of the atoms and ions being 4500 and 5500 K, respectively, and the ionization temperature being about 6000 K.Notation I absolute spectral line intensity (W cm^–2 sr^–1) - emission coefficient (W cm^–3 sr^–1) - A relative absorption - absorption coefficient (cm^–1) - L plasma diameter (mm) - f _tk oscillator strength - _D full Doppler width (cm^–1) - S( ₀ L) Ladenburg-Levy function - wave number (cm^–1) - k _pl mass transport rate (mol cm^–2 s^–1) - k _th thermal reduction rate (mol cm^–2 s^–1) - u ion mobility (mm V^–1 s^–1 ) - E electric field strength (V mm^–1) - drift velocity (cm s^–1)     

Low temperature absorption spectra of CrO 4 = in K2SO4 and VO 4 ≡ in Na3PO4 · 12H2O

The polarized absorption spectrum of the chromate ion has been measured at liquid hydrogen and helium temperatures. With chromate dissolved in K₂SO₄ evidence is found for two orbitally allowed ¹ A ₁¹ T ₂ electronic absorption bands. The first band is split into three sublevels with the 0-0 lines located at 26,316 cm^–1, 26,441 cm^–1 and 26,610 cm^–1. Built upon the 0-0 lines is seen a simple progression in quanta of 783 cm^–1. The second transition is nearly featureless, and is found at 34,000 cm^–1 to 44,000 cm^–1. The two bands are assigned as primarily t ₁2e and as 3t ₂2e respectively.VO ₄ dissolved in Na₃PO₄ · 12H₂O showed at liquid nitrogen temperature a broad featureless band found between 30,000 and 40,000 cm^–1.

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Zusammenfassung Das polarisierte Absorptionsspektrum des Chromations wurde bei den Temperaturen des flüssigen Wasserstoffs und Heliums gemessen. Für Chromat in K₂SO₄ werden zwei erlaubte Absorptionsbanden ¹ A ¹¹ T ₂ gefunden. Die erste Bande ist dreifach aufgespalten, ihre 0-0 Linien liegen bei 26316 cm^–1, 26441 cm^–1 und 26610 cm^–1. Von den 0-0 Linien ausgehend zeigt sich eine einfache Zunahme der Werte um 783 cm^–1. Der zweite Übergang ist nahezu strukturlos, er liegt zwischen 34000 cm^–1 und 44000 cm^–1. Die beiden Banden werden überwiegend t ₁2e bzw. 3t ₂2e zugeordnet. VO ₄ in Na₃PO₄ · 12H₂O zeigt bei der Temperatur des flüssigen Stickstoffs eine breite strukturlose Bande zwischen 30 000 und 40 000 cm^–1.

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Résumé Le spectre d'absorption en lumière polarisée de l'ion chromate a été mesuré aux températures de l'hydrogène et de l'hélium liquide. Pour le chromate dissous dans K₂SO₄ on met en évidence deux bandes d'absorption électronique de transition orbitale permise ¹ A ₁¹ T ₂. La première bande est séparée en trois sous niveaux dont les raies 0-0 se trouvent à 26,316 cm^–1, 26,441 cm^–1 et 26,610 cm^–1. A partir des raies 0-0 on distingue une période de 783 cm^–1. La seconde bande est presque non structurée et s'étend de 34,000 cm^–1 à 44,000 cm^–1. Les deux bandes sont décrites comme t ₁2e et 3t ₂2e respectivement.VO ₄ dissous dans Na₃PO₄ · 12H₂O révèle à la température de l'azote liquide une large bande sans structure entre 30,000 et 40,000 cm^–1.

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On leave of absence from Anorganisch Chemisch Laboratorium der Universiteit, Amsterdam.     

Coordination chemistry of alkali and alkaline earth cations: Crystal structure of rubidium (benzo-15-crown-5)2NO3·H2O

The complex Rb(B15C5)₂NO₃·H₂O is monoclinic,P2_1/c,a=12.695(3),b=19.471(3),c=12.991(2)Å, =99.60(2)^o,V=3166 ų,D _c =1.473 g/cm³ (163 K),D _c =1.434 g/cm³ (298 K),D _o =1.44 g/cm³ (298 K),T=163K,Z=4, MoK=0.71069 Å, 2(4^o–53^o), =16.43 cm^–1,F(000)=1424. FinalR for the 4588 observed reflections (F>3) is 0.062. All ten oxygens of the two benzo-crowns are shown to coordinate to the rubidium ion (Rb...O,2.92 to 3.07 Å) forming a charge-separated sandwich. The nearest nitrate oxygen is displaced 6.51 Å from the rubidium ion and is hydrogen bonded to a water molecule. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82028 (28 pages)     

Theoretical Study of Chemical Binding of Noble Gas Atom and Transition Metal Complexes: Ng–NiCO, Ng–NiN2, Ng–CoCO (Ng = He–Xe)

Ab initio multireference and coupled cluster methods (MR-SDCI(+Q), CASPT2, CCSD(T)) and density functional theory methods (B3LYP, MPWPW91) have been applied to examine geometrical structures and vibrational frequencies of noble gas (Ng) – transition metal compounds, Ng–NiCO, Ng–NiN₂, and Ng–CoCO (Ng = He, Ne, Ar, Kr, Xe). It is shown that the respective compounds can have a larger binding energy than a typical van der Waals interaction energy. The binding mechanism is explained by a partial electron transfer from a noble gas atom to the low-lying 4s and 3d vacant orbitals of the transition metal atom. Theoretical calculations show that the binding of noble gas atom results in a large shift of the bending frequency: 361.1cm^–1 (NiCO) to 403.5cm^–1 (Ar–NiCO); 308.5cm^–1 (NiN₂) to 354.8cm^–1 (Ar–NiN₂); 373.0cm^–1 (CoCO) to 422.6cm^–1 (Ar–CoCO). The corresponding experimental frequencies determined in solid argon are 409.1cm^–1 (NiCO), 357.0cm^–1 (NiN₂), and 424.9cm^–1 (CoCO), which are much closer to the corresponding frequency of Ar–NiCO, Ar–NiN₂, and Ar–CoCO, respectively.     

Die Schwingungsspektren einiger Pentadeuterophenylphosphorverbindungen

The vibrational spectra of C₆D₅PX ₂, (C₆D₅)₂PX (X=H, Cl), (C₆D₅)₃P and of the Cyclophosphanes (PC₆H₅) _n and (PC₆D₅) _n (n=5, 6) are reported. The spectra of the phenylphosphorouscompound D (the structure beeing unknown) are given too. The C₆H₅/C₆D₅ isotopic shift data in the lower frequency-region (600–100 cm^–1) (facilitating the recognition of vibrational coupling effects) are used for vibrational assignments.

     

Accurate analytic potential energy function and spectroscopic study for CH(XΠ) radical using coupled-cluster theory in combination with the correlation-consistent quintuple basis set

The coupled-cluster singles-doubles-approximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set (aug-cc-pV5Z) is used to investigate the spectroscopic properties of the CH(X²Π) radical. The accurate adiabatic potential energy curve is calculated over the internuclear separation ranging from 0.07 to 2.45 nm and is fitted to the analytic Murrell–Sorbie function, which is employed to determine the spectroscopic parameters, ω_eχ_e, α_e and B_e. The present D_e, R_e, ω_e, ω_eχ_e, α_e and B_e values are of 3.6261 eV, 0.11199 nm, 2856.312 cm⁻¹, 64.9321 cm⁻¹, 0.5452 cm⁻¹ and 14.457 cm⁻¹, respectively. Excellent agreement is obtained when they are compared with the available measurements. With the potential obtained at the CCSD(T)/aug-cc-pV5Z level of theory, a total of 18 vibrational states is predicted when J = 0 by numerically solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced for the CH(X²Π) radical when J = 0 for the first time, which are in good agreement with the available RKR data.     

Molecular Structures and Vibrational Spectra of ScF3, YF3, and LaF3 as Calculated by the CISD+Q Method

Molecular structures and vibrational spectra of ScF₃, YF₃, and LaF₃ were studied by the Hartree–Fock– Roothaan method in terms of second-order Möller–Plesset perturbation theory and by the configuration interaction method including all singly and doubly excited configurations and Davidson's correction for quartic excitations (CISD+Q). The atomic core orbitals are defined in terms of the effective relativistic potentials suggested by Stevens et al. The equilibrium nuclear configuration is shown to be planar (D _3h symmetry) for ScF₃ and YF₃ and pyramidal (C _3v ) for LaF₃ with a bond angle . The inversion barrier of LaF₃ is very low: h = E(D _3h )- E(C _3v ) = 38 cm ^–1 (CISD+Q). The vibrational spectra were calculated by the variational method using the vibrational Hamiltonian describing the nonrigidity of a molecule with respect to out-of-plane deformation. The calculation results are compared with the previously published experimental data. The IR band assignments for matrix-isolated molecular conformations in a vapor over yttrium trifluoride were corrected.     

Theoretical Study of Chemical Binding of Noble Gas Atom and Transition Metal Complexes: Ng–NiCO, Ng–NiN2, Ng–CoCO (Ng = He–Xe)

Summary. Ab initio multireference and coupled cluster methods (MR-SDCI(+Q), CASPT2, CCSD(T)) and density functional theory methods (B3LYP, MPWPW91) have been applied to examine geometrical structures and vibrational frequencies of noble gas (Ng) – transition metal compounds, Ng–NiCO, Ng–NiN₂, and Ng–CoCO (Ng = He, Ne, Ar, Kr, Xe). It is shown that the respective compounds can have a larger binding energy than a typical van der Waals interaction energy. The binding mechanism is explained by a partial electron transfer from a noble gas atom to the low-lying 4s and 3d vacant orbitals of the transition metal atom. Theoretical calculations show that the binding of noble gas atom results in a large shift of the bending frequency: 361.1cm^–1 (NiCO) to 403.5cm^–1 (Ar–NiCO); 308.5cm^–1 (NiN₂) to 354.8cm^–1 (Ar–NiN₂); 373.0cm^–1 (CoCO) to 422.6cm^–1 (Ar–CoCO). The corresponding experimental frequencies determined in solid argon are 409.1cm^–1 (NiCO), 357.0cm^–1 (NiN₂), and 424.9cm^–1 (CoCO), which are much closer to the corresponding frequency of Ar–NiCO, Ar–NiN₂, and Ar–CoCO, respectively.     

Neutral molecule/crown ether interactions 5. Comparison of the C−H acidic interactions of nitromethane and acetonitrile with 18-crown-6 and dibenzo-18-crown-6. Crystal structures of dibenzo-18-crown-6·2 CH3NO2 and dibenzo-18-crown-6·2 CH3CN

Complete structural characterization of dibenzo-18-crown-6·2 CH₃NO₂ and dibenzo-18-crown-6·2 CH₃CN have been carried out, including location and refinement of the methyl hydrogen atoms. Dibenzo-18-crown-6·2 CH₃NO₂ is monoclinic,P2₁/c, with (at –150°C)a=9.573(2),b=14.636(2),c=33.471(7) Å, =93.77(2)°, andD _calc=1.37 g cm^–3 forZ=8. Interactions between the solvent methyl groups and the crown ethers and other solvent nitro groups associate the 1 : 2 complexes into polymeric chains alongb. The acetonitrile adduct exists as discreet 1 : 2 complexes in the solid state with C–H...O interactions exlusively to the ether. This complex is triclinic,P 1, with (at –150°C)a=9.458(6),b=9.570(5),c=14.404(5) Å, =73.18(4), =79.85(5), =66.82(6)°, andD _calc=1.28 g cm^–3 forZ=2. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82070 (22 pages).For part 4, see reference [1].     

Molecular constants for the 1Σ+ ground state of the ArH+ ion

From the near equilibrium PNO-CEPA potential and dipole moment curves the following molecular constants for the ¹⁺ ground state of the ArH⁺ ion have been calculated: r _e = 1.286Å, _e = 2723 cm^–1, _{e e} = 56 cm^–1, D ₀ = 3.89 eV and ₀ = 2.384 D. The rotationless radiative lifetimes of the five lowest vibrational states are predicted to be 2.28, 1.2, 0.85, 0.64, 0.46 for ArH⁺ and 9.09, 4.71, 3.27, 2.55 and 2.11 for ArD⁺, respectively (all values are in milliseconds and in ascending order of the vibrational levels).Dedicated to Prof. Hermann Hartmann on the occasion of his 65th birthday.     

Coordination chemistry of alkali and alkaline earth cations. Barium-crown encapsulation studies: The synthesis and crystal structure of barium(picrate)2(benzo-15-crown-5) monohydrate

The interaction of barium with benzo-15-crown-5 (B15C5) has been followed under the competitive effect of various chelating organic anions (L), nitrophenolates and nitrobenzoates, in ethanol and ethanol-water (9:1). The rather heavily hydrated BaL₂ salts yield novel 1:1 stoichiometric products in monohydrated or anhydrous states. Use of excess crown does not under any condition lead to the formation of 1:2 charge separated complexes, expected in view of the cavity and the cation sizes. The 1:1 Ba–B15C5 interaction is counteracted by L in accordance with its nucleophilicity, i.e., the pK _a value of its parent acid, HL. The complex Ba(picrate)₂(B15C5)·H₂O (BaC₂₆H₂₆N₆O₂₀, FW=879.0), is monoclinic,P2₁/c,a=11.43(1),b=16.31(3),c=17.38(2) Å, =92.265(3)°,Z=4,D _c=1.77 g/cm³,D ₀=1.73 g/cm³, MoK, =0.71069 Å, 2 (4.0–50°), =13.5 cm^–1,F(000)=1752,T=–32°C. FinalR for the 5926 reflections was 0.049. The structure reveals barium to be 10-coordinated through all the five crown oxygens (Ba–O, 2.800 to 3.002 Å), the two bidentate picrates (Ba–O, 2.642 and 2.666 Å; Ba–ONO, 2.825 and 2.994 Å), and the water molecule (2.711 Å) so that the cation constitutes a pseudo-sandwich of the crown on one side and the anionic species on the other. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82007 (50 pages). To obtain copies, see page ii of this issue.     

Coordination chemistry of alkali and alkaline earth cations: Synthesis and crystal structure of potassium(benzo-15-crown-5)2 [3,5-dinitrobenzoate(3,5-dinitrobenzoic acid)2]

The interaction of K(35-Dnb) (35-Dnb=3,5-dinitrobenzoate) with benzo-15-crown-5 (B15C5) in ethanol yields a charge-separated sandwich structured complex [K(B15C5)₂]⁺[35-Dnb(35-DnbH)₂]^– even when equimolar amounts of reactants were used and no external 35-DnbH was added to the reaction mixture. The complex (KC₄₉H₅₁O₂₈N₆, FW=1211.1), is monoclinic,P2₁/c,a=11.063(2),b=10.680(1),c=46.548(8) Å, =91.629(2)⁰,Z=4,D ₀=1.485 g/cm³,D _c=1.468 g/cm³, CuK =1.5418 Å, =17.01 cm^–1, 2<130⁰,F(000)=2520,T=298 K. FinalR for the 6618 observed reflections was 0.071. In the sandwich moiety, the K⁺ is 10-coordinated through all the oxygens of the crown molecules (K⁺–O, 2.76–3.11 Å). The 35-Dnb anion lies 5.3 Å below the lower crown mean plane and is charge separated with respect to K⁺ (K⁺–O^–>7 Å) but undergoes strong hydrogen bonding (2.59 and 2.49 Å) through each carboxylate oxygen with the carboxylic protons of two separate 35-DnbH molecules. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82014 (52 pages).     

Structural study of the 1:1 clathrate of an asymmetric calix[4]arene and acetone

The crystal and molecular structure of the 1:1 clathrate of the asymmetric calix[4]arene,1, and acetone has been determined by X-ray analysis. The crystal data are: tetragonal, space groupP4/n,a=b=12.574(6),c=12.572(6) Å,V=1988(2) ų,Z=2,D _x =1.111 g cm^–3,D _m =1.108 g cm^–3. Least-squares refinement based on 1131 observed reflections withF ₀>3(F ₀) and anisotropic temperature factors led toR=0.096. In spite of the molecular asymmetric calixarene1 the crystal structure has high symmetry, because a part of the host and guest molecules are in disordered states.     

Über Reaktionen von Arylbiguaniden mit Benzoin beimpH der Biguanidbasen

Summary Arylbiguanides2 a–e react with benzoin (1) at thepH of the base to two different products.1 undergoes in presence of the base2 a–e oxidation to benzil and benzoic acid, which reacts fast with the arylbiguanides2 a–e to yield N-[4-(arylamino)-6-phenyl-1,3,5-triazine-2-yl]benzamides3 a–d. After lowering thepH of the reaction mixture, the bases2 b–e react with benzil to yield 2-[1-aryl-5-oxo-4,4-diphenyl-2-imidazoline-2-yl]guanidine4 b–e. The mechanism of the formation is discussed. The structure of4b was established from a single crystal x-ray structure analysis. The analysis was carried out at 100K: C₂₃H₂₁N₅O,M _r=383.5, monoclinic, C 2/c,a=15.842(6),b=8.419(3),c=30.223(10) Å, =98.44(3)°,V=3 987.3(9) ų,Z=8,d _x=1.277 g/cm³, =0.81 cm^–1,R=5.89%R _w=4.97% (1 537 observations, 233 parameters).

     

MD Simulation of an Infinitely Dilute Aqueous Solution of Formamide. Study of Thermodynamic, Structural, Dynamic, and Spectroscopic Properties

A molecular dynamics simulation of an infinitely dilute aqueous solution of formamide was carried out using an MP2-CP ab initio potential to describe the solute–solvent interaction. Various static and dynamic properties were calculated using this potential obtained by fitting the formamide–water interaction energies to a 12-6-1 type function. These energies were calculated with the supermolecular approach by considering the MP2 correlation and the CP superposition. The values presented for the thermodynamic functions (H _S–W = –25.5 kcal-mol^–1 and G _S–W = –15.9 kcal-mol^–1), the structure of the first hydration layer (with 5 to 6 solvent molecules bonded to the solute), the solute's translational (D= 1.50 × 10^–5 cm²-s^–1) and rotational ( = 6.6 ps) mobility in the surrounding medium, and the positions of the H···O hydrogen bond spectral bands corresponding to these motions (_i = 92, 246, 379, and 636 cm^–1), are in agreement with the available results for this and other similar systems. In addition, the results are compared with those obtained by using parameters transferred from other systems. We observed that these values depend strongly on the potential used and concluded that it is advisable to avoid the use of such parameters.     

Neutral solvent/crown ether interactions 3. Reorientation of the hydrogen bonds in the low temperature (−150°C) structure of 18-crown-6·2(CH3NO2)

The title complex was crystallized from a saturated solution of 18-crown-6 in nitromethane at 5°C and cooled to –150°C prior to X-ray diffraction data collection. At –150° C 18-crown-6·2(CH₃NO₂) is monoclinic,P2₁/_n witha=9.290(2),b=7.864(6),c=13.627(8) Å, =1000.84(4)° andD _calc=1.31 g cm^–3 for Z=2. Leastsquares refinement using 1521 independent observed reflections [F _o5(F _o)] led to a final conventionalR value of 0.041. The complex at –150°C is isostructural with its room temperature structure with the exception of the orientation of the methyl hydrogen atoms and their crown ether oxygen interactions. The methyl group hydrogen atoms were fully refined isotropically. The crown ether resides around a center of inversion and hasD _3d symmetry. There is one methyl hydrogen...crown interaction at 2.35(3) Å, one apparently bifurcated hydrogen bond utilizing a second methyl hydrogen atom (2.55(3), 2.65(3) Å) and the third hydrogen atom is actually directed away from the crown ring (closest H...O contact=2.67(3) Å). Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82048 (5 pages).For part 2, see reference [24].