Nucleophilic addition of bifunctional sulfimidosulfides to platinum(<Emphasis Type="SmallCaps">IV</Emphasis>)-coordinated nitriles

Reactions of the platinum(IV) nitrile complexes [PtCl₄(RCN)₂] (R = Me, CH₂Ph, Ph) with 1,2- and 1,4-PhS(=NH)C₆H₄SPh in CH₂Cl₂ afforded addition products of sulfimides and coordinated nitriles, viz., the [PtCl₄{NH=C(R)N=S(Ph)(C₆H₄SPh)}₂] complexes. The latter were isolated in 75—90% yields and characterized by elemental analysis, positive-ion FAB mass spectrometry, IR spectroscopy, and ¹H and ¹³C¹H NMR spectroscopy. The temperature dependence of the ¹H NMR spectra of the model [PtCl₄{NH=C(R)N=SPh₂}₂] complexes (R = Me, Et) in CD₂Cl₂ studied in a temperature range from +40 to -70 °C demonstrated that E—Z isomerization of the ligands is a dynamic process in a range from +40 to -10 °C. The activation free energy of this process was calculated.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1618–1622, August, 2004.     

Antiferromagnetic coupling in [Mn<Subscript>12</Subscript>O<Subscript>12</Subscript>(O<Subscript>2</Subscript>CMe)<Subscript>6</Subscript>(<Emphasis Type="Italic">p</Emphasis>-CO<Subscript>2</Subscript>-phenyl nitronyl

The synthesis of [Mn₁₂O₁₂(O₂CMe)₆(p-CO₂-phenyl nitronyl nitroxide)₁₀(H₂O)₄]· 4H₂O, (1), by direct replacement of some of the acetate groups in [Mn₁₂O₁₂(O₂CMe)₁₆(H₂O)₄] · 4H₂O · 2MeCO₂H, (2), with the organic radical p-HO₂C-phenyl nitronyl nitroxide, (3), is reported. E.p.r. spectra show exchange narrowing in (1) due to coupling between the manganese ions and radicals. The isotropic hyperfine splitting constant from the manganese ions is a = 96 Oe at 5.5K. The magnetic susceptibility indicates antiferromagnetic exchange interactions between the manganese ions and the radicals with the Weiss constant = -25 K. The spin was determined to be S = 6 from magnetization data in the 2--30 K temperature range at 50 kOe, suggesting a mixture of ground state with excited states.     

Action of HCl on 3-hydroxypyrazolo(iso)quinolines to give 1-chloropyrazoles: evidence for an addition–elimination mechanism by ab initio calculations in gas phase and water

 Addition–elimination reactions involving a nucleophile and a remote leaving group [S^H _N(AE)^tele] are well-known under basic conditions, especially amongst electron-poor six-membered heterocycles, but are less commonly encountered for five-membered heterocycles and are rare under acidic conditions. Concentrated HCl converts 1-hydroxy-1H-pyrazolo[3,4-c] isoquinoline and 1-hydroxy-1H-pyrazolo[3,4-c]quinoline into 3-chloro-1H-pyrazolo[3,4-c]isoquinoline and 3-chloro-1H-pyrazolo[3,4-c]quinoline, respectively. However, apparently neither the isomeric 1-hydroxy-1H-pyrazolo[4,3-c](iso)-quinolines nor the parent 1-hydroxypyrazole undergo this reaction. Additionally, all these systems are refractory under basic conditions. We present a plausible mechanism for the reaction, involving the 3-addition of Cl^- to the diprotonated heterocycle, followed by the elimination of water. Calculations of the initial transition states and intermediates, using optimisation at B3LYP/6-311+G(d,p), including thermochemistry [HF/6-31+G(d)], and single-point Poisson–Boltzmann self-consistent reaction field determination of the free energy of solvation (Jaguar Poisson–Boltzmann self-consistent reaction field), support this mechanism and reproduce the observed order of reactivity, the addition step being 2–4 kcal less favourable for the isomeric 1-hydroxy-1H-pyrazolo[4,3-c](iso)quinolines and provide a rationalisation for the role of strong acid. Received: 27 June 2002 / Accepted: 6 September 2002 / Published online: 14 February 2003     

Quantification of monohydroxy-PAH metabolites in urine by solid-phase extraction with isotope dilution-GC–MS

For measurement of biomarkers from polycyclic aromatic hydrocarbon (PAH) exposure, an analytical method is described quantifying hydroxylated PAH (OH-PAH) in urine samples. This method determined monohydroxy metabolites of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[c]phenanthrene, and benz[a]anthracene. The sample preparation consisted of enzymatic hydrolysis, solid-phase extraction and derivatization with a silylating reagent. Five carbon-13 labeled standards were used for isotope dilution. Analytes were separated by gas chromatography (GC) and quantified with high-resolution mass spectrometry (HRMS). This method produced good recoveries (41-70%), linearity, and specificity. Data were corrected for blank levels from the naphthalene, fluorene, and phenanthrene metabolites. Method detection limits ranged from 2 ng L(-1) for 1-hydroxypyrene to 43.5 ng L(-1) for 1-hydroxynaphthalene. Using quality control charts from two urine pools, the method can be readily applied to biomonitoring PAH exposure.     

Lanthanum chromites partially substituted by calcium,strontium and barium synthesized by urea combustion

Because of their electrical, magnetic and catalytic properties rare earth and transition metal mixed oxides are important compounds. Lanthanum chromites have been extensively used as solid oxide fuel cell (SOFC) interconnect materials. In this work, lanthanum chromites partially substituted by alkaline earth metals were synthesized by the urea combustion process. TG and DSC techniques were used to evaluate the presence of the organic material in the powder after reaction on the hot plate. The powders were calcinated at 900°C and characterized by XRD and SEM. The results show that the particles have nanometric dimensions and the perovskite structure was formed.     

Inherent instabilities of some W5Si3-type binary phases with large electropositive metal atoms: Six examples in the Ba-Pb, Ca-Sn-Mg,Cu,Zn, and La-Ga-Al,Zn systems

A particular pathology of certain W₅Si₃-type A₅B₃ structures (I4/mcm) appears to arise because of unduly close approaches of the A1-type atoms on the cell faces at , 0, () that occur with the larger and more electropositive A and/or in the presence of smaller B atoms. A structure refinement of binary Ba_4.81Pb₃ indicates such a marginal stability in that the Ba atoms in the facial Ba_0.81 chains exhibit an extreme displacement ellipsoid along . Although Ca₅Sn₃ and La₅Ga₃ binaries are unknown in this structure type, five stable ternary derivatives of these have been synthesized via substitution reactions and characterized by single crystal X-ray diffraction means: Ca₄Sn_3.223(4)Mg_0.777, Ca₄Sn₃Cu_1.30(4), Ca_4.66(6)Sn₃Zn_0.704(4), La_4.81(1)Ga_1.38(2)Al_1.62, and La_4.762(5)Ga_1.5(1)Zn_1.5. Only the Ca-Sn-Zn phase exhibits lower symmetry, P4/mbm. The problematic A1 sites exhibit diverse changes in these, whereas the surrounding B2 tetrahedra are largely unaltered. The Ca-Sn results are, respectively: direct Mg/Sn substitution at the Ca1 site; mixed fractional distribution of the smaller Cu at two sites around the A1 position with an unresolved disorder; a pair of apparently independent modes, fractional Ca in the normal position and fractional Zn rectangles thereabout. The two La-Sn phases contain normal Ga,Al (Ga,Zn) tetrahedral chains with pairs of fractional disordered La atoms along , 0, z. Each can be rationalized in terms of a reasonable incommensurate structure. Electronic effects may also be operable.     

Novel method for bulk resistance evaluation in conductivity measurement for high-purity water

A major issue with the electrolytic conductivity measurement for pure water is the lack of standard or reference methods. A primary method traceable to SI and suitable for pure-water conductivity measurement was developed at the Physikalisch-Technische Bundesanstalt (PTB), Germany, as the base for the calibration method for the conductivity measuring devices at the low conductivity level. This paper provides a novel method to calculate the bulk resistance of pure water using impedance measured at a single frequency, which is one of the key procedures for the primary methods.     

Syntheses and characterization of three hybrid materials based on polymeric copper complexes and saturated Keggin polyoxoanions

Three novel heteropolytungstates, [Cu(phen)₂]₄[α-SiW₁₂O₄₀] (1), [Cu₄(4,4′-bpy)₃(2,2′-bpy)₄][α-SiW₁₂O₄₀] · H₂O (2) and [Cu(4,4′-bpy)(4,4′-Hbpy)_0.5]₂[PW₁₂O₄₀] (3) (phen = 1,10-phenanthroline, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine), have been synthesized and characterized by elemental analyses, IR, TG analyses and single-crystal X-ray diffraction. Compound (1) exhibits interesting chiral layer constructed from interperpendicular helical chains running along a crystallographic 2₁ axis in the c and a directions. Furthermore, the chiral layers are connected by the [α-SiW₁₂O₄₀]⁴⁻ anions via hydrogen bonding interactions to form a 3D superamolecular structure. The [Cu₄(4,4′-bpy)₃(2,2′-bpy)₄]⁴⁺ coordinated complexes in compound (2) are packed together via the aromatic π–π stacking interactions and exhibit an interesting 3D sandglasslike “host” network with 1D channels, in which [α-SiW₁₂O₄₀]⁴⁻ anions “guests” reside. Compound (3) has a unique 2D superamolecular network, which is composed of cationic Cu^I coordination polymer chains and discrete [PW₁₂O₄₀]³⁻ polyoxoanions as linkers. It is noteworthy that the monprotonated 4,4′-bpy ligands of (3) act as arms and connect the adjacent 2D network, generating a 3D interpenetrating superamolecular structure.     

Pentanuclear Ba(II) complex of a macrocyclic ligand

We report here the first pentanuclear Ba(II) complex of a new tri-aza, tri-oxa macrocycle with two carboxymethyl "arms" pending from two N atoms, H2L2. The crystal structure corresponds to the formula [Ba5(H0.375L2)4(ClO4)(CH3CH2OH)(H2O)2](ClO4)2.5 x 9.5H2O and reveals the presence of four molecules of the ligand surrounding five Ba(II) ions, giving rise to an unusual structure with the metal ions inside a spherical organic cavity.