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.     

Collision energy effect on the H′ + BrH (ν = 0, j = 0) → H′Br + H reaction: A quasi-classical trajectory study

Theoretical studies on the dynamics of the exchange reaction H′ + BrH (ν = 0, j = 0) → H′Br + H are performed on potential energy surface (PES) (Kurosaki et al., private communication) for the ground state using the quasi-classical trajectory method. The cross sections, computed at the collision energies (E_c) of 0.5-2.0 eV, are in good agreement with the earlier quantum wave packet results. The rotational, vibrational, and translational fractions in the total energy and the vibrational distribution for the product molecule are calculated at the same collision-energy range. The results support the repulsive character of the PES. In the considered E_c range, it has little chance to occur in an indirect reaction. The alignment and orientation of the product H′Br are investigated in detail with stereodynamics. The results show that E_c can effect on both the alignment and the orientation of product.     

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.     

Theoretical insight into stereodynamics of the O(D) + H2 (v = 0–3, j = 0) → OH + H reaction: A quasiclassical trajectory (QCT) study

In this work, the reaction O(¹D) + H₂ → OH + H has been theoretically studied using the quasiclassical trajectory (QCT) method developed by Han and co-workers. All the quasiclassical trajectory calculations are performed on the DK (Dobbyn and Knowles) potential energy surface (PES). The vector correlation information on the reaction O(¹D) + H₂ → OH + H has been obtained. It has been demonstrated that the product alignment is sensitive to the reactant vibrational quantum number (v) at collision energy of 19 kcal/mol. Moreover, with increasing the value of v, backward scattering becomes weaker and forward scattering becomes stronger.     

Solid–liquid metastable equilibria in the quaternary system Li2SO4 + MgSO4 + Na2SO4 + H2O at T = 263.15 K

Solubility in the liquid–solid metastable system Li₂SO₄ + MgSO₄ + Na₂SO₄ + H₂O at T = 263.15 K was studied using the isothermal evaporation method. Based on experimental data, dry-salt phase and water-phase diagrams of the system were plotted. The dry-salt phase diagram of the system includes one three-salt co-saturation point, three metastable solubility isotherm curves, and three crystallization regions corresponding to lithium sulphate monohydrate (Li₂SO₄·H₂O), epsomite (MgSO₄·7H₂O), and mirabilite (Na₂SO₄·10H₂O). Neither a solid solution nor double salts were found. Based on the extended Harvie–Weare (HW) model and its temperature-dependent equation, the values of the Pitzer parameters β⁽⁰⁾, β⁽¹⁾, β⁽²⁾, and C^Φ for Li₂SO₄, MgSO₄, and Na₂SO₄, the mixed ion-interaction parameters θ_Li,Na, θ_Li,Mg, θ_Na,Mg, ΨLi,Na,SO₄${\Psi }_{\text{Li,Na,S}{\text{O}}_4}$, ΨLi,Mg,SO₄${\Psi }_{\text{Li,Mg,S}{\text{O}}_4}$, and ΨNa,Mg,SO₄${\Psi }_{\text{Na,Mg,S}{\text{O}}_4}$, and the Debye–Hückel parameter A^Φ in the quaternary system at 263.15 K were obtained. The solubility of the quaternary system Li₂SO₄ + MgSO₄ + Na₂SO₄ + H₂O at T = 263.15 K was also calculated. A comparison between the calculated and experimental results shows that the predicted solubility agrees well with experimental data.     

Spin fluctuations and orbital ordering in quasi-one-dimensional α-Cu(dca)2(pyz) {dca = dicyanamide = N(CN)2; pyz = pyrazine}, a molecular analogue of KCuF3

The magnetic properties of α-Cu(dca)₂(pyz) were examined by magnetic susceptibility, magnetization, inelastic neutron scattering (INS), muon-spin relaxation (μSR) measurements and by first-principles density functional theoretical (DFT) calculations and quantum Monte Carlo (QMC) simulations. The χ versus T curve shows a broad maximum at 3.5 K, and the data between 2 and 300 K is well described by an S = 1/2 Heisenberg uniform chain model with g = 2.152(1) and J/k_B = −5.4(1) K. μSR measurements, conducted down to 0.02 K and as a function of longitudinal magnetic field, show no oscillations in the muon asymmetry function A(t). This evidence, together with the lack of spin wave formation as gleaned from INS data, suggests that no long-range magnetic order takes place in α-Cu(dca)₂(pyz) down to the lowest measured temperatures. Electronic structure calculations further show that the spin exchange is significant only along the Cu–pyz–Cu chains, such that α-Cu(dca)₂(pyz) can be described by a Heisenberg antiferromagnetic chain model. Further support for this comes from the M versus B curve, which is strongly concave owing to the reduced spin dimensionality. α-Cu(dca)₂(pyz) is a molecular analogue of KCuF₃ owing to d_x2-y2${\text{d}}_{x^2-y^2}$ orbital ordering where nearest-neighbor magnetic orbital planes of the Cu²⁺ sites are orthogonal in the planes perpendicular to the Cu–pyz–Cu chains.     

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.     

[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.     

On the synthesis and structures of the complexes [RuCl(L)(dppb)(N–N)]PF6 (L = CO,py or 4-NH2py; dppb = 1,4-bis(diphenylphosphino)butane; N–N = 2,2′-bipyridine or 1,10-phenanthroline) and [(dppb)(CO)Cl2-Ru-pz-RuCl2(CO)(dppb)] (pz = pyrazine)

The “Ru(P–P)” unit (P–P = diphosphine) is recognized to be an important core in catalytic species for hydrogenation of unsaturated organic substrates. Thus, in this study we synthesized six new complexes containing this core, including the binuclear complex [(dppb)(CO)Cl₂Ru-pz-RuCl₂(CO)(dppb)] (pz = pyrazine) which can be used as a precursor for the synthesis of cationic carbonyl species of general formula [RuCl(CO)(dppb)(N–N)]PF₆ (N–N = diimine). Complexes with the formula [RuCl(py)(dppb)(N–N)]PF₆ were synthesized by exhaustive electrolysis of these carbonyl compounds or from the precursors [RuCl₂(dppb)(N–N)]. The new complexes were characterized by microanalysis, conductivity measurements, IR and ³¹P{¹H} NMR spectroscopy, cyclic voltammetry and X-ray crystallography.     

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.     

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.     

A reversible solid–solid phase transition Z′ = 1 to Z′ = 6 in [Ni(OAc)(PNP)]OTf

At ambient temperature, the complex [Ni(OAc)(PNP^tBu)]OTf has one independent molecule in the asymmetric unit of the crystal structure with very large anisotropic displacement parameters. During cooling a fully reversible solid–solid phase transition occurs at a discrete temperature in the range 210–230 K. The low-temperature phase has six independent, well ordered molecules in the asymmetric unit. The P2₁/a space group symmetry of the high-temperature phase changes to P2₁/n for the low-temperature phase and the c-axis increases by a factor of six. The acetate ligand is shown to be coordinated in a η¹-fashion through one of the oxygen atoms, with the sterically encumbered, tridentate PNP^tBu ligand completing the square planar geometry around the Ni^II ion. The synthesis and full characterization of the complex is reported.     

Ag adsorption on Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1?) surfaces: First-principles investigations

First-principles calculations are performed to study the adsorption of Ag at Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1?) surfaces as a function of Ag coverage. Our results reveal that Ag adsorption at Cd-terminated (0 0 0 1) has a large binging energy than at S-terminated (0 0 0 1?) surface. For Ag adsorption at Cd-terminated (0 0 0 1) surface, T4 structure is more favorable and the Ag-Cd bond posses an ionic-like character. While for Ag adsorption at S-terminated (0 0 0 1?) surface, the H3 structure is most stable and the bonding between Ag-S is covalent. It is found that the magnitude and the sign of surface dipole moment are partly determined by the difference between the electronegativities of Ag and the host atom bonding with Ag. The adsorption energy changes as a function of Ag coverage. In addition, related properties of Ag cluster adsorption at Cd-terminated (0 0 0 1) surface are also discussed.     

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.     

A series of multinuclear homo- and heterometallic complexes with bridging tellurolato ligands derived from [CpIr(CO)(TeTol)2] (Cp = η-C5Me5, Tol = p-tolyl)

Reactions of [Cp^∗Ir(CO)(TeTol)₂] (1; Tol = p-tolyl) with certain organometallic Pd(II), Pt(II), Ir(III), Rh(III), and Ru(II) species afforded IrPd, IrPt, IrPt₂, Ir₂, IrRh, IrRu₃, and IrRu complexes having tellurolato-bridged dinuclear or trinuclear cores. This finding demonstrates that 1 is a versatile precursor to synthesize a variety of multinuclear homo- and heterometallic μ-tellurolato complexes, whose chemistry is still less advanced as compared with that of μ-thiolato complexes.     

Syntheses, structures, and dynamic properties of M(CO)2(η-C3H5)(en)(X) (M = Mo, W; X = Br, N3, CN) and [(en)(η-C3H5)(CO)2M(μ-CN)M(CO)2(η-C3H5)(en)]Br (M = Mo, W)

Mononuclear compounds M(CO)₂(η³-C₃H₅)(en)(X) (X = Br, M = Mo(1), W(2); X = N₃, M = Mo(3), W(4); X = CN, M = Mo(5), W(6)) and cyanide-bridged bimetallic compounds [(en)(η³-C₃H₅)(CO)₂M(μ-CN)M(CO)₂(η³-C₃H₅)(en)]Br (M = Mo (7), W(8)) were prepared and characterized. These compounds are fluxional and display broad unresolved proton NMR signals at room temperature. Compounds 1-6 were characterized by NMR spectroscopy at −60 °C, which revealed isomers in solution. The major isomers of 1-4 adopt an asymmetric endo-conformation, while those of 5 and 6 were both found to possess a symmetric endo-conformation. The single crystal X-ray structures of 1-6 are consistent with the structures of the major isomer in solution at low temperature. In contrast to mononuclear terminal cyanide compounds 5 and 6, cyanide-bridged compounds 7 and 8 were found to adopt the asymmetric endo-conformation in the solid state.     

High-efficiency hydrophilic interaction chromatography by coupling 25 cm × 4.6 mm ID × 5 μm silica columns and operation at 80 °C

Recently, hydrophilic interaction chromatography (HILIC) has emerged as a valuable orthogonal tool to reversed-phase liquid chromatography (RP-LC) as it allows for resolution of highly polar ionisable compounds. The relationships between separation efficiency, column length and speed of analysis for 4.6 mm ID × 5 μm silica particle columns in HILIC are demonstrated using kinetic plots. The kinetic plots constructed for conventional pressure systems operating at 350 bar and at 30 °C and 80 °C are confirmed using experimental data for different column lengths. Efficiencies of more than 130,000 theoretical plates could be achieved by connecting up to six columns of 25 cm. As expected, a significant gain in analysis speed without loss of efficiency could be obtained by operating at 80 °C compared to 30 °C. The advantages of using long columns in HILIC in combination with elevated column temperature for the pharmaceutical industry are illustrated using test mixtures comprised of commercially available ionisable compounds (including some containing functional groups with potential genotoxic typical structural alerts) as well as real polar ionisable pharmaceuticals.     

Polymeric assembling through reciprocal metal-η-arene π-interactions: Synthesis and X-ray characterization of [Hg(RPhNNNPhR′)2Py]2 (R = NO2, R′ = F), an asymmetric bis diaryl-substituted triazenide-pyridinyl complex of Hg(II)

Hg(SCN)₂ reacts with 3-(2-fluorophenyl)-1-(4-nitrophenyl)triazene in tetrahydrofuran in the presence of triethylamine to give orange crystals of [Hg^II(RPhNNNPhR′)₂Py]₂ (R = NO₂, R′ = F), a new polymeric triazenide-pyridinyl complex of Hg(II) with reciprocal metal-η²-arene π-interactions. The crystal structure belongs to the triclinic space group , and the lattice of [Hg^II(RPhNNNPhR′)₂Py]₂ can be viewed as a supramolecular unidimensional assembling of tectonic [Hg^II(RPhNNNPhR′)₂Py] units linked through intermolecular metal-arene π interactions and non-classical C-H?O hydrogen bonding.     

Synthesis and characterization of mono and polymeric cyclopalladated compounds: Crystal and molecular structure of [{Pd(dmba)(ONO2)}2(μ-pz)] · H2O (pz = pyrazine)

In the treatment of cyclometallated dimer [Pd(dmba)(μ-Cl)]₂ (dmba = N,N-dimethylbenzylamine) with AgNO₃ and acetonitrile the result was the monomeric cationic precursor [Pd(dmba)(NCMe)₂](NO₃) (NCMe = acetonitrile) (1). Compound 1 reacted with m-nitroaniline (m-NAN) and pirazine (pz), originating [Pd(dmba)(ONO₂)(m-NAN)] (2) and [{Pd(dmba)(ONO₂)}₂(μ-pz)] · H₂O (3), respectively. These compounds were characterized by elemental analysis, IR and NMR spectroscopy. The IR spectra of (2–3) display typical bands of monodentade O-bonded nitrate groups, whereas the NMR data of 3 are consistent with the presence of bridging pyrazine ligands. The structure of compound 3 was determined by X-ray diffraction analysis. This packing consists of a supramolecular chain formed by hydrogen bonding between the water molecule and nitrato ligands of two consecutive [Pd₂(dmba)₂(ONO₂)₂(μ-pz)] units.     

Syntheses and crystal structures of [Bu3SbCr(CO)5], [Bu3BiM(CO)5] (M = Cr, W), and [Bu3BiMnCp′(CO)2] (Cp′ = η-C5H4CH3)

Syntheses and crystal structures of [^tBu₃SbCr(CO)₅] (1), [^tBu₃BiM(CO)₅] [M = Cr (2), W (3)] and [^tBu₃BiMnCp′(CO)₂] (4) (Cp′ = η⁵-C₅H₄CH₃) are reported.