Temperature dependence of nonequivalent potential wells for pyridinium ion reorientation in pyridinium tetrachloroiodate(III), PyHICl4, studied by 1H-14N nuclear quadrupole double resonance

The reorientation of a pyridinium ion in the paraelectric and antiferroelectric phase of PyHICl(4) is investigated using (1)H-(14)N nuclear quadrupole double resonance (NQDR). The (14)N nuclear quadrupole resonance frequencies are measured. The temperature variations of the principal values of the time-averaged electric-field-gradient (EFG) tensor at the nitrogen position are used to determine the occupation probabilities of the six orientations of a pyridinium ion in both crystallographic phases. The energy difference between various orientations is determined. The molar transition entropy associated with the reorientation of the pyridinium ions is calculated and compared to the experimental value.     

Studies in werner clathrates. Part 2. Structures of bis (isothiocyanato) tetra (4-phenylpyridine) nickel (II)· 4-dimethylsulphoxide,bis (isothiocyanato) tetra (3-methylpyridine) nickel (II)· chloroform and bis (isothiocyanato) tetra (3,5-dimethylpyridine) nickel (II)

The structures of Ni(NCS)₂(4-PhPy)₄·4DMSO and Ni(NCS)₂(3-MePy)₄·CHCl₃ have been elucidated. Movement of guest molecules through channels in the host structure was simulated by potential energy calculations. Ni(NCS)₂(3,5-diMePy)₄ does not form inclusion compounds. An intra-molecular potential energy study shows that theortho-hydrogens on the 3,5-dimethylpyridine ligands control the conformation of the molecule. The same result is obtained with the 4-methylpyridine ligand, which suggests that the extent of rotation of substituted pyridines about the Ni–N bounds is not a factor governing clathrate formation. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82030 (43 pages).     

Studies on werner clathrates. Part 131. Selective criteria in werner clathrates. Six crystal structures with bis(isothiocyanato)tetra(4-vinylpyridine)nickel(II) as host

This paper addresses the general question: what are the significant guest properties selected by this host when interacting with guest molecules in the liquid phase, resulting in cocrystallization of the host and guest? In particular, to what extent do π electrons in a guest molecule effect its potential as a guest? Werner clathrates of the host [Ni(NCS)₂(4-ViPy)₄] with mixtures of tetrahydrofuran (THF) and cyclic hydrocarbons as guests have been synthesised and their structures elucidated. Clathrate (1): [Ni(NCS)₂(4-ViPy)₄](1.78 THF)(0.22 cyclohexane), crystallizes in the orthorhombic space groupP _bcn a=9.976(6),b=20.630(25),c=19.861 (4) Å,V=4087ų,Z=4,R=0.087 for 1461 reflections; (2): [Ni(NCS)₂(4-ViPy)₄](1.76 THF)(0.24 cyclohexene),P _bcn ,a=9.987(7),b=20.614(4),c=19.898(4)Å,V=4096ų,Z=4,R=0.084 for 1304 reflections; (3): [Ni(NCS)₂(4-ViPy)₄](0.48 THF)(0.52 1,3-cyclohexadiene), tetragonalI4₁/a,a=16.898(3),b=16.898(3),c=26.463(6)Å,V=7556ų,Z=8,R=0.120 for 1698 reflections; (4): [Ni(NCS)₂(4-ViPy)₄](0.36 THF)(1.04 1,4-cyclohexadiene),I4₁/a,a=16.986(4),b=16.986(4),c=25.896(15)Å,V=7472ų,Z=8,R=0.103 for 2025 reflections; (5): [Ni(NCS)₂(4-ViPy)₄](0.35 THF)(1.05 benzene),I4₁/a,a=17.102(10),b=17.102(10),c=25.498(8)Å,V=7458ų,Z=8,R=0.118 for 2200 reflections; (6): [Ni(NCS)₂(4-ViPy)₄](3 benzene), triclinicP1,a=10.432(24),b=11.155(9),c=21.581(7)Å, α=78.70(5), β=82.60(7), γ=74.09(13)°,V=2361ų,Z=2,R=0.078 for 3427 reflections. Host-guest ratios and, for mixtures of guests, guest1/guest2 ratios, were elucidated by density and NMR. We show that the conformational freedom of the substituted pyridines is not the primary reason for the clathrating ability of Werner hosts. All six structures show no host-guest interaction at the level of van der Waals interactions. As non-bonding interactions are not observed between the host and guest, this study shows that the above host's selectivity by enclathration of particular guest molecules cannot be accounted for by solid state structural analysis.     

Complexes of heteroscorpionate trispyrazolylborate ligands. Part XI. Weak CH/π interactions in crystals of hydrotris(3-phenylpyrazolyl)boratothallium(I) and hydrobis(5-methyl-3-phenylpyrazolyl)(3,5-dimethylpyrazol-yl)boratothallium(I) studied by X-ray crystallography

Thallium(I) complexes of heteroscorpionate hydrobis(3-phenyl-5-methylpyrazolyl)(3,5-dimethylpyrazol-yl)borate and hydrotris(3-phenylpyrazol-1-yl)borate were studied crystallographically. Both ligands were coordinated in κ³ fashion via N₂ atoms of pyrazol-1-yl moieties. Both compounds crystallize as centrosymmetric dimers in which weak CH/π intra- and interdimer interactions are responsible for arrangement in crystal structure.     

Synthesis and crystal structure of Cu(I) and Ni(II) complexes of 1,1-diethyl-3-(4-fluorobenzoyl)-thiourea

The reaction of 1,1-diethyl-3-(4-fluorobenzoyl)-thiourea (HL) with CuCl₂ ·?2H₂O and NiCl₂ ·?6H₂O give two complexes, Cu(HL)₃Cl (1) and NiL₂ (2). The crystal structures of these products were determined by single crystal X-ray diffraction. In 1, three HL molecules are unidentate, coordinating through the sulfur, and the copper is tetrahedral with three S and one Cl. In 2, two HL molecules are O and S donor bidentate and coordinate as anionic species with loss of the proton from the acyl-substituted nitrogen; the nickel is square-planar.     

ChemInform Abstract: Relativistic Effects in Gold Chemistry. Part 4. Gold(III) and Gold(V) Compounds

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Coordination of solvent molecules to VO(acac)<Subscript>2</Subscript> complexes in solution studied by hyperfine sublevel correlation spectroscopy and pulsed electron nuclear double resonance

Interactions and binding sites of the solvent molecules chloroform and ethanol to bis(acetylacetonate)oxovanadium(IV) (VO(acac)₂) complexes in (frozen) solutions have been investigated by pulsed electron nuclear double resonance, sum peak electron spin echo envelope modulation and hyperfine sublevel correlation spectroscopy. The experimental proton hyperfine coupling data of coordinating solvent molecules have been interpreted using quantum chemical calculations (density functional theory). Experimental and computed hyperfine couplings indicate that ethanol coordinates to vanadium in the equatorial plane of VO(acac)₂ and chloroform interacts via hydrogen bonding to oxygens of the acac ligands.     

The W2Cl4(NHCMe3)2(PR 3)2 molecules (R 3=Me3, Et3, Pr n 3, Me2Ph) I. Their isomeric forms,interconversion proeesses,crystalline forms,and detailed molecular structures

A thorough study of compounds with the formula W₂Cl₄(NHCMe₃)2(PR₃)₂, withR ₃=Me₃, Et₃, Prg ⁿ ₃ Me₂,Ph, is reported. In addition to the previously reported crystalline compounds, namely Ia,trans-W₂Cl₄(NHCMe₃)₂(PMe₃)₂ in space group Pmmn;3a,trans-W₂Cl₄(NHCM₃)₂(PEt₃)₂ in space group P2₁/^a (or P2₁/^c); and4,cis-W₂Cl₄(NHCMe₃)₂(PMe₂Ph)₂ in Pna2₁, we have obtained and structurally characterized the following new substances,1b,trans-W₂Cl₄,(NHCMe₃)₂(PMe₂)₂, space group P2₁/^c,a= 12.233 (4) Å,b= 12.872 (4) Å,c=17.095 (5) Å,=93.52 (2)°,Z=4,V=2687 (1) ų 2,cis-W₂Cl₄(NHCMe₃)₂(PMe₃)₂, P2₁/^c,a=9.673 (4) Å,b=17.249 (4) Å,c=16.244 (5) Å,=99.63 (3),Z = 4 ,V=2669 (1) Å.3b,trans-W₂Cl₄(NHCMe₃)₂(PEt₃)₂, Pl,a=16.850 (3) Å,b=17.797 (3) Å,c= 11.459 (2)Å,= 101.02 (1),= 103.13°, y=84.23 (1)°,Z=4,V= 3279 (1) Å5,trans-W₂Cl₄(NHCM₃)₂(PMe₂Ph)₂, Fdd2,a=39.563 (8) Å at 20°C; 39.325 (10) Å at -6O°C,b = 57.543 (17) Å at 20°C; 57.186 (16) Å at -60°C,c= 8.810 (1) Å at 20°C; 8.770 (1) Å at - 60°C ,Z=24,V=20057 (7) ų (20°C), 19723 (8) ų ( - 60°C) .6,trans-W₂Cl₄(NHCMe_{3 2}(PPrⁿ ₃)₂, Pl,a= 17.287 (2) Å (20°C); 17.077 (5) Å (-60°C),b= 19.119 (2) Å (20°C); 18.952 (6) Å (-60°C),c= 12.713 (1) Å (20°C); 12.668 (4) Å (-60°C),Z=4,V= 3980 (1) ų (20°C), 3898 (2) ,ų ( - 60°C). In addition, the structure of3a was re-determined and refined so that the disorder ratio was a refined parameter, leading to a value of 0.520:0.480 instead of being arbitrarily fixed at 0.50:0.50. In all of the structures the molecules are held in eclipsed (but very distorted) rotational conformations and the W-W distances are all within the range of 2.305-2.330 Å. As will be shown in a later paper, for all phosphines, thecis andtrans isomers are of similar stability and an equilibrium mixture exists in solution. It is also shown that1a and3a do not contain unexpectedly short W-N bonds as previously reported.     

Tetraiododiborane(4) (B2I4) is a Polymer Based on sp3 Boron in the Solid State

Herein we present the first solid‐state structures of tetraiododiborane(4) (B₂I₄), which was long believed to exist in all phases as discrete molecules with planar, tricoordinate boron atoms, like the lighter tetrahalodiboranes(4) B₂F₄, B₂Cl₄, and B₂Br₄. Single‐crystal X‐ray diffraction, solid‐state NMR, and IR measurements indicate that B₂I₄ in fact exists as two different polymeric forms in the solid state, both of which feature boron atoms in tetrahedral environments. DFT calculations are used to simulate the IR spectra of the solution and solid‐state structures, and these are compared with the experimental spectra.     

ChemInform Abstract: Theoretical versus Experimental Charge and Spin-Density Distributions in trans-(Ni(NH3)4(NO2)2).

A comparison of data from three different theoretical models (ab initio UHF and DVXα MO calculations as well as cellular ligand field analysis (clf)) with experimental charge and spin-density distributions, obtained from X-ray and polarized neutron diffraction results, leads to a consistent picture of the electronic structure and M-L bonding in the title complex.     

Clathrate and inclusion compounds: Part V. An infrared and Raman study of the decomposition of the Hofmann aniline clathrates M(NH3)2Ni(CN)4.2C6H5NH2 {M = Cd(II) and Ni(II)}

The time-dependent changes which are observed in the infrared and Raman spectra of samples of the two Hofmann aniline clathrates M(NH₃)₂Ni(CN)₄.an₂ {M = Cd(II), Ni(II), an = C₆H₅NH₂} indicate the occurrence of a solid state ligand replacement reaction in which the aniline guest molecule replaces the coordinated ammonia to give Man₂Ni(CN)₄ as the final product. The rate of replacement is greater for the cadmium than for the nickel clathrate, and for both clathrates evacuation of the sample greatly increases the rate of replacement. The Man₂Ni(CN)₄ complexes can themselves act as host lattices forming clathrates containing guest molecules such as aniline.     

Thermodynamic analysis of equilibria between binary liquid and solid solutions in ternary systems. Application to systems in which two guests compete for sites in the same host,tetrakis(4-methylpyridine)nickel(II) isothiocyanate

A thermodynamic analysis is presented of the equilibria between liquid solutions of guest A in guest B and solid solutions of HA in HB, where HA and HB are isomorphous 1:1 compounds of these guests with the host H. (The treatment is applicable whether or not HA and HB are inclusion compounds.) The mole ratio of A to B in the liquid,R ₁, is generally different from the same ratio in the solid,R _s. Data on many systems have indicated a linear relation between InR ₁, and InR _s, but to date no theoretical basis has been forthcoming. The present analysis shows that this relation is usually sigmoidal in shape but, with certain restrictions, is nearly linear. The slope and intercept are interpreted in terms of the equilibrium constant for the displacement of A from HA by B and the deviations from ideality in the liquid and solid phases. If the deviations from ideality in the liquid phase are known or can be estimated, those for the solid phase can be determined, and thermodynamic equilibrium constants and standard free energy changes for the displacement of A by B calculated. These methods were applied to available data for the following pairs of guests with the host Ni(4-mepy)₄(NCS)₂:p-xylene with each ofp-dibromobenzenp-xylene-d₆,p-xylene-d ₁₀,p-bromotoluene,p-chlorotoluene,p-dichlorobenzene,p-fluorotoluene, ethylbenzene, toluene, and benzene, and the pairsp-dichlorobenzene/p-chlorotoluene and ethylbenzene/ toluene.     

Temperature dependence of121Sb nuclear quadrupole resonance frequencies in the spectra of M2Sb2SO4F6 (M = K,Rb, NH4)

The temperature dependence of the frequencies of¹²¹Sb nuclear quadrupole resonance in the spectra of M₂Sb₂SO₄F₆ (M = K, Rb, NH₄) was studied in the temperature range from 77 to 340 K. A secondary phase transition was found above 320 K for (NH₄)₂SO₄F₆.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1831–1833, October, 1994.This study was sponsored by the Russian Foundation for Basic Research (Grant No. 93-03-4394).     

Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) studied with paramagnetic spin probes. I. Electron spin resonance spectra

Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) was studied as a function of the butadiene content and method of preparation with electron spin resonance (ESR) spectra of nitroxide spin probes. Results for the ABS polymers were evaluated by comparison with similar studies of the homopolymers polybutadiene (PB), polystyrene (PS), and polyacrylonitrile (PAN) and the copolymers poly(styrene‐co‐acrylonitrile) (SAN) and poly(styrene‐co‐butadiene) (SB). Two spin probes were selected for this study: 10‐doxylnonadecane (10DND) and 5‐doxyldecane (5DD). The probes varied in size and were selected because their hydrocarbon backbone made them compatible with the polymers studied. The ESR spectra were measured in the temperature range 120–420 K and were analyzed in terms of line shapes, line widths, and hyperfine splitting from the ¹⁴N nucleus; the appearance of more than one spectral component was taken as an indication of microphase separation. Only one spectral component was detected for 10DND in PB, PS, and PAN and in the copolymers SAN and SB. In contrast, two spectral components differing in their dynamic properties were detected for both probes in the three types of ABS samples studied and were assigned to spin probes located in butadiene‐rich domains (the fast component) and SAN‐rich domains (the slow component). The behavior of the fast component in ABS prepared by mass polymerization suggested that the low‐T_g (glass‐transition‐temperature) phase was almost pure PB. The corresponding phase in ABS prepared by emulsion grafting also contained styrene and acrylonitrile monomers. A redistribution of the spin probes on heating occurred with heating near the T_g of the SAN phase, suggesting that the ABS polymers as prepared were not in thermodynamic equilibrium. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 415–423, 2002; DOI 10.1002/polb.10109     

Tin(IV) and organotin(IV) derivatives of novel β-diketones: Part IV. Triorganotin(IV) complexes of fluorinated 4-acyl-5-pyrazolones. Crystal structure of (1-(4-trifluoromethylphenyl)-3-methyl-4-acetylpyrazolon-5-ato)triphenyltin(IV)

The synthesis of three 1-(4-trifluoromethylphenyl)-3-methyl-4-R¹(C=O)-5-pyrazolone proligands LH (L¹H; R¹=C₆H₅: L²H; R¹=CH₃: L³H; R¹=CF₃) and their interaction with R₃Sn(IV) acceptors (R=Me, Buⁿ, Ph) are reported. When R=Me or Buⁿ, aquo (4-acylpyrazolonate)SnR₃(H₂O) derivatives are obtained and the anionic donors 4-acylpyrazolonate (L⁻) act in the O–monodentate form. These triorganotin complexes are not stable in chlorohydrocarbon solvents and decompose to R₄Sn and bis(4-acyl-5-pyrazolonate)₂SnR₂. When R=Ph, stable (4-acyl-5-pyrazolonate)SnPh₃ derivatives, both in solution and in the solid state, are obtained. The crystal structure of (1-(4-trifluoromethylphenyl)-3-methyl-4-acetylpyrazolon-5-ato)triphenyltin(IV) shows a five-coordinate tin atom in a strongly distorted cis-bipyramidal trigonal environment (axial angle=161.2(2)°) with the acylpyrazolonate donor acting as an asymmetric O₂–bidentate species (Sn–O(1)=2.081(6) Å: Sn–O(2)=2.424(5) Å). Electronic effects are responsible for the different behavior shown by these trialkyl and triphenyl derivatives.     

Novel Isatin-Schiff Base Cu (II) and Ni(II) Complexes. X-ray Crystal Structure of Bis[3-(4-hexylphenylimino)-1H-indol-2(3H)-one]-dichlorocopper(II) Complex

Schiff bases of isatin were reported to possess antibacterial, antifungal, antiviral, anti-HIV, antiprotozoal, and anthelmintic activities1. They also exhibit significantanticonvulsant activity, apart from other pharmacological properties2. Conductingsubs…