Vapor–liquid equilibria and density measurement for binary mixtures of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF at 333.15 K, 343.15 K and 353.15 K from 0 kPa to 101.3 kPa

Isothermal vapor–liquid equilibria at 333.15 K, 343.15 K and 353.15 K for three binary mixtures of o-xylene, m-xylene and p-xylene individually mixed with N-methylformamide (NMF), have been obtained at pressures ranged from 0 kPa to 101.3 kPa over the whole composition range. The Wilson, NRTL and UNIQUAC activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Peng–Robinson equation of state in calculating the vapor mole fraction. Liquid and vapor densities were measured by using two vibrating tube densitometers. The excess molar volumes of the liquid phase were also determined. Three systems of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF mixtures present large positive deviations from the ideal solution and belong to endothermic mixings because their excess Gibbs energies are positive. Temperature dependent intermolecular parameters in the NRTL model correlation were finally obtained in this study.     

Germylene and stannylene (Me2NCH2CH2O)2E as strong σ-donor ligands for transition metal complexes [ML(CO)n] (E = Ge, Sn; M = Cr, Mo, W, n = 4 or 5; M = Fe, n = 4). Synthesis, spectroscopic and theoretical study

A series of germylene and stannylene (Me₂NCH₂CH₂O)₂E (E = Ge, 1; E = Sn, 2) complexes of group 6 metals and iron carbonyls L·M(CO)_n (M = Cr, Mo, W, n = 5 (3-8), n = 4 (9, 10); M = Fe, n = 4 (11, 12)) were prepared. These complexes were characterized by ¹H, ¹³C NMR, FTIR and elemental analysis. Ligand properties of 1 and 2 were compared to PPh₃ and dmiy (N,N′-dimethylimidazolin-2-ylidene) using theoretical calculations (PBE/TZ2P) and FTIR. Ligand dissociation energies increase in the order Ph₃P < 2∼1 < dmiy, while donor strength rise in the order PPh₃ < dmiy < 2 < 1.     

Are closed clusters expected from the (n + 1) skeletal electron pairs rule in alanes and gallanes? A DFT structural study of AnHn + 2 (A = Al, Ga, and n = 4-6)

It has been suggested recently that the alanes Al_nH_n + 2 can be treated by the polyhedral skeletal electron pair theory (PSEPT) of Wade and Mingos (W-M) as it was successful for their borane congeners such as B_nH_n + 2, well known as the deprotonated B_nH_n²⁻. To do so, the neutral Al_nH_n + 2 have been considered as Al_nH_n²⁻ + 2H⁺. The additional hydrogens donate their electrons to the Al_nH_n polyhedral framework and according to the n + 1 electron pairs rule; these clusters should have closo-polyhedral structures. In this work the homologous gallanes, the structures and stabilities of Ga_nH_n + 2 are studied at high levels of calculational theory and we investigated the applicability of the W-M rule to the alanes and gallanes A_nH_n + 2 (n = 4-6; A = Al, Ga). It will be shown that the presence of bridging hydrogen atoms reduces the compactness of the corresponding polyhedron and so these species do not have the closed structures. The computations were performed at B3LYP/6-311+G(d,p), BPW91/6-311G(d,p) and B3LYP/6-311+G(3df,2p) levels of theory. Our interest in these compounds includes their potential use as hydrogen storage species and future clean sources of energy.     

Isobaric vapor–liquid equilibrium for binary mixtures of 1-hexene + n-hexane and cyclohexane + cyclohexene at 30, 60 and 101.3 kPa

Consistent vapor–liquid equilibria (VLE) data were determined for the binary systems 1-hexene + n-hexane and cyclohexane + cyclohexene at 30, 60 and 101.3 kPa, with the purpose of studying the influence of the pressure in the separation of these binary mixtures. The two systems show a small positive deviation from ideality and do not present an azeotrope. VLE data for the binary systems have been correlated by the Wilson, UNIQUAC and NRTL equations with good results and have been predicted by the UNIFAC group contribution method.     

Insertion reaction of elemental sulfur into the Ln–C bond: Synthesis and characterization of [(C5H4SiMe2Bu)2Ln(μ-SR)]2 (R = Me,Ln = Yb,Er, Dy,Y; R = Bu,Ln = Yb,Dy)

Treatment of (C₅H₄SiMe₂^tBu)₂LnR with 1 equiv of elemental sulfur in toluene at ambient temperature gives dimeric complexes [(C₅H₄SiMe₂^tBu)₂Ln(μ-SR)]₂ [R = Me, Ln = Yb (1), Er (2), Dy (3), Y (4); R = ⁿBu, Ln = Yb (5), Dy (6)]. All these complexes have been characterized by elemental analysis, IR and mass spectroscopies. The structures of complexes 1, 3, 5 and 6 are also determined through X-ray single crystal diffraction analysis, indicating that only one sulfur atom from elemental sulfur inserts into Ln–C σ-bond.     

HMB and Cp* ruthenium(II) complexes containing bis- and tris-(mercaptomethimazolyl)borate ligands: Synthetic, X-ray structural and electrochemical studies (HMB = η-C6Me6, Cp* = η-C5Me5)

The reactions of [(HMB)RuCl₂]₂ with K[HB(mt)₃] and Na[H₂B(mt)₂] (mt = N-methyl-2-mercaptoimidazol-1-yl) led to the isolation of [(HMB)Ru{HB(mt)₃}]Cl (1) (ca. 66% yield) and [(HMB)Ru{H₂B(mt)₂}]Cl (2) (ca. 70% yield), respectively. The reaction of [Cp*RuOMe]₂ with Na[H₂B(mt)₂] yielded Cp*Ru[H₂B(mt)₂] (3) (ca. 85% yield). Single crystal X-ray diffraction analyses were carried out on all three complexes, together with cyclic voltammetric measurements.     

Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(L-L)(NCBH3) (M = Mo, W; L-L = dppe, bipy, en)

Compounds M(CO)₂(η³-C₃H₅)(L-L)(NCBH₃) (L-L = dppe, M = Mo(1), W(2); L-L = bipy, M = Mo(3), W(4); L-L = en, M = Mo(5), W(6)) were prepared and characterized. The single crystal X-ray analyses of 2-6 revealed that the cyanotrihydroborate anion bonds to the metal through a nitrogen atom, the open face of the allyl group being pointed toward the two carbonyls (endo-isomer). In compounds 2, 5, and 6, the two donor atoms of the bidentate ligand occupy equatorial and axial positions, respectively. In the solid state structures of compounds 3 and 4 both nitrogen atoms of the bipy ligand occupy equatorial positions. The NMR spectroscopy reveals a fluxional behavior of compounds 1, 2, 5, and 6 in solution. Although the fluxional behavior of compounds 5 and 6 ceased at about −40 °C, that of compound 1 could not be stopped even at −90 °C. Their low temperature conformations are consistent with their solid state structures. Both the endo- and exo-isomers coexist in solution for compounds 3 and 4.     

Vapor–liquid equilibria and density measurement for binary mixtures of toluene,benzene, o-xylene,m-xylene,sulfolane and nonane at 333.15 K and 353.15 K

Isothermal vapor–liquid equilibria at 333.15 K and 353.15 K for four binary mixtures of benzene + nonane, toluene + o-xylene, m-xylene + sulfolane and o-xylene + sulfolane have been obtained at pressures ranged from 0 to 101.3 kPa over the whole composition range. The Wilson, NRTL and UNIQUAC activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Peng–Robinson equation of state in calculating the vapor mole fraction. Liquid and vapor densities of these solutions were measured by using two vibrating tube densitometers. The excess molar volumes of the liquid phase were also determined. The P–x–y phase behavior indicates that mixtures of m-xylene + sulfolane, o-xylene + sulfolane and benzene + nonane present large positive deviations from the ideal solution and belong to endothermic mixings because their excess Gibbs energies are positive.     

[M(dipicH2)(H2O)3], M = Ni,Cu, Zn (dipicH2 = dipicolinic acid) – A combined crystallographic,spectroscopic and computational study

Cationic metal complexes of dipicolinic acid (dipicH₂) are stabilized by [Ce(dipic)₃]²⁻ ions in the three isomorphous crystals [M(dipicH₂)(OH₂)₃][Ce(dipic)₃] · 3H₂O (M = Ni, 1; Cu, 2; Zn, 3). Magnetic dilution provided by the bulky anions leads to well-resolved EPR spectra in polycrystalline samples of 2. The cations have 4+2 coordination, the carbonyl atom of the carboxylic acid groups coordinating weakly from trans positions. In the case of 2 this steric distortion is augmented by Jahn–Teller distortion. All the three structures are satisfactorily modelled by calculations based on density functional theory (DFT). The switch of the Jahn–Teller axis upon deprotonation of the complex, leading to the neutral species Cu(dipic)(H₂O)₃, is also reproduced by DFT. Electronic transition energies as well as the g-tensor component of the d⁹ complex obtained are in good agreement with experiment. However, the calculated hyperfine coupling constants are in error. DFT also fails to satisfactorily account for the electronic transition in the d⁸ ion in 1.     

Theoretical study of the structure and stability of cage-substituted icosahedral closo-boranes, alanes, and gallanes MiM′12 ? iH 122? (M, M′ = B, Al, and Ga; i = 0–12)

The equilibrium geometric parameters and energetic and spectroscopic characteristics of low-lying conformers for several series of model cage-substituted (mixed) borane, alane, and gallane closo-dianions M _i M′_{12 − i} H₁₂²⁻(M, M′ = B, Al, Ga), as well as of “bare” gallium-aluminum anions Ga _i Al_12−i ⁻ with i = 0–12, were calculated within the B3LYP approximation of the density functional theory using 6–31G* and 6–311+G** basis sets. Differences in structure and stability between alanoborane clusters of similar composition are revealed. In clusters where the M and M’ heteroatoms are close in size and electronegativity (in gallonoalanes and gallium-aluminum anions), successive substitutions of M′ for M are accompanied by small energy changes and occur quasi-stochastically in different positions of the cage. When the substituents are significantly different (in alanoboranes), mixed clusters are unstable against disproportionation into homonuclear “predecessors” M₁₂H₁₂²⁻ and M′₁₂H₁₂²⁻, and the most favorable M _i M′_{12 − i} H₁₂²⁻ structures among them are those in which M _i M′_{12 − i} the cages are subdivided into homonuclear “subclusters” M _i and M′t′_12−i with a maximal number of homonuclear bonds (M-M and M′-M′) and a minimal number of heteronuclear bonds (M-M′).     

Vapor–liquid equilibrium in the n-butane + methanol system,measurement and modeling from 323.2 to 443.2 K

New experimental vapor–liquid equilibrium (VLE) data for the n-butane + methanol binary system are reported over a wide temperature range from 323.2 to 443.2 K and pressures up to 5.4 MPa. A static–analytic apparatus, taking advantage of two pneumatic capillary samplers, was used. The phase equilibrium data generated in this work are in relatively good agreement with previous data reported in the literature. Three different thermodynamic models have been used to represent the new experimental data. The first model is the cubic-based Peng–Robinson equation of state (EoS) combined with the Wong–Sandler mixing rules. The two other models are the non-cubic SAFT-VR and PC-SAFT equations of state. Temperature-dependent binary interaction parameters have been adjusted to the new data. The three models accurately represent the new experimental data, but deviations are seen to increase at low temperature. A similar evolution of the binary parameters with respect to temperature is observed for the three models. In particular a discontinuity is observed for the k_ij values at temperatures close to the critical point of butane, indicating the effects of fluctuations on the phase equilibria close to critical points.     

Isobaric vapor–liquid equilibria for the n-hexane + 2-isopropoxyethanol and n-heptane + 2-isopropoxyethanol systems

Vapor–liquid equilibria (VLE) for the n-hexane + 2-isopropoxyethanol and n-heptane + 2-isopropoxyethanol (at 60, 80, and 100 kPa) systems were measured. Two systems present positive deviations from ideal behavior. And the system n-heptane + 2-isopropoxyethanol shows a minimum boiling azeotrope at all pressures. Experimented data have been correlated with the two term virial equation for vapor-phase fugacity coefficients and the three suffix Margules equation, Wilson, NRTL, and UNIQUAC equations for liquid-phase activity coefficients. Experimental VLE data show excellent agreements with models.     

Vapor–liquid equilibrium for the binary systems tetrahydrothiophene + toluene and tetrahydrothiophene + o-xylene at 368.15 K and 383.15 K

Isothermal vapor–liquid equilibrium (VLE) for tetrahydrothiophene + toluene and tetrahydrothiophene + o-xylene at 368.15 K and 383.15 K was measured with a recirculation still. Liquid- and vapor-phase compositions were determined with gas chromatography. All systems exhibit a small positive deviation from Raoult's law and show nearly ideal behavior. All VLE measurements passed the point test used. The experimental results were correlated with the Wilson model and compared with COSMO-SAC predictive models. COSMO-SAC predictions show a slight negative deviation from Raoult's law for all systems measured. Raoult's law can be used to describe all systems studied. The activity coefficients at infinite dilution are presented.     

Variation of radiative lifetimes of NH2(Ã2A1) with rotational levels in the (0, 8, 0) and (0, 9, 0) vibration bands

Radiative lifetimes from the first electronically excited state of the amidogen free radical, NH(2)(A?(2)A(1)), are reported for rotational states in selected vibrational levels ν(2)' using laser-induced fluorescence. Thermal collision of argon, Ar(?)((3)P(0), (3)P(2)) metastable atoms in a microwave discharge-flow system with ammonia (NH(3)) molecules produced ground state NH(2)(X?(2)B(1)). The radiative lifetimes for the deactivation of NH(2)(A?(2)A(1)) were determined by measuring the decay profiles of NH(2)(A?(2)A(1)?→?X?(2)B(1)). In addition to the Fermi resonances with the ground state that lengthen the radiative lifetimes, a systematic increase in the radiative lifetimes with rotational quantum number was observed. Furthermore, the average radiative lifetimes of the (0, 9, 0) Γ, τ(1) = 18.65 ± 0.47 μs and (0, 8, 0) Φ, τ(2) = 23.72 ± 0.65 μs levels were much longer than those of the (0, 9, 0) Σ, τ(3) = 10.62 ± 0.47 μs, and (0, 8, 0) Π, τ(4) = 13.55 ± 0.55 μs states suggesting increased mixing of the first electronic excited and the ground states.     

Synthesis, X-ray crystal structure, and reactivity of Pd2(μ-dotpm)2 (dotpm = bis(di-ortho-tolylphosphino)methane)

Alkylation of PdCl₂(dotpm) (dotpm = bis(di-ortho-tolylphosphino)methane) with n-butyllithium produces the binuclear Pd(0) complex Pd₂(μ-dotpm)₂ and the elimination byproducts 1-butene, cis-2-butene, trans-2-butene, butane, and octane. The dibutyl complex, Pd(dotpm)(n-Bu)₂, is presumed to be the reaction intermediate. The crystal structure of Pd₂(μ-dotpm)₂ reveals that the methylene groups of the bridging dotpm ligands are located on opposite sides of the Pd₂P₄ unit, forming an 8-membered ring that is in an elongated chair conformation. The four phosphorus atoms are not coplanar, and the P1-P2-P3-P4 ring has a torsion angle of 13.8°, which minimizes the spatial interactions among the o-tolyl rings. The Pd-Pd bond distance is 2.8560(6) Å, which indicates that there is a weak “closed-shell” bonding interaction between the d¹⁰-d¹⁰ metal centers. Each palladium atom has a nearly linear geometry, and the eight methyl groups of the dotpm ligands shield the open coordination sites on the metal centers. Four methyl groups shield the metal atoms above and below the Pd₂P₄ ring cavity, and four methyl groups block the open metal sites outside of the Pd₂P₄ ring. The Pd₂(μ-dotpm)₂ complex readily undergoes oxidative addition of dichloromethane to form the rigid A-frame complex Pd₂Cl₂(μ-CH₂)(μ-dotpm)₂.     

Synthesis and structures of CpFe(CO)2(κE-ECS2Ph) and [CpFe(CO)(κS,E-ECS2Ph)] (E = S,Se)

The iron trithiocarbonato complex CpFe(CO)₂(κS-SCS₂Ph) (1a) and its selenodithiocarbonato analogue CpFe(CO)₂(κSe-SeCS₂Ph) (1b) were generated by room temperature reactions of (μ-E_x)[CpFe(CO)₂]₂ (E = S; x = 2, 3. E = Se; x = 1) with PhSC(S)Cl. These compounds can be converted into the complexes CpFe(CO)(κ²S,E-ECS₂Ph) [E = S (2a), Se (2b)], in which the trithiocarbonato or the selenodithiocarbonato ligand is bonded to the iron in a chelate form, under photolytic conditions. The composition and structure of all products have been verified by elemental analyses, IR and ¹H NMR spectroscopies. The crystal structures for compounds 1a, 1b, and 2b show a three-legged piano-stool configuration at Fe in each complex. The spectroscopic and structural data in this work are commensurate with the electronic factor of the S- and Se-donor ligands.