Modified Merrifield resin-supported PCP pincer palladium nanoparticles as a new polymeric catalyst for cyanation of aryl iodides

A new tridentate PCP pincer palladium (Pd) complex based on cross-linked Merrifield resin containing phosphinite ligand was synthesized and characterized. This polymeric catalyst was used in preparation of benzonitriles from different aryl iodides using potassium hexacyanoferrate (II) as a cyanide source. The presence of active metallic Pd in the catalyst was verified by X-ray power diffraction and X-ray photoelectron spectroscopy techniques. Transmission electron microscopy showed good dispersion of catalytic sites in the range of 30–50 nm. The catalyst is easily separated from reaction mixture and can be used for several times in repeating cycles without considerable loss of activity. The leaching of Pd from the support is negligible, which was confirmed by inductively coupled plasma–optical emission spectrometry and hot filtration test.     

Synthese und Kristallstrukturen der Phosphaniminato-Komplexe [SbF2(NPEt3)]2 und [SbF(NPEt3)2]2 sowie von NMe4+SbF4−

Synthesis and Crystal Structures of the Phosphoraneiminato Complexes [SbF₂(NPEt₃)]₂ and [SbF(NPEt₃)₂]₂ as well as of NMe₄⁺SbF₄^? The title compounds have been prepared from antimony trifluoride with the silylated phosphaneimine Me₃SiNPEt₃ and [NMe₄]F, respectively. They were characterized by IR spectroscopy and by crystal structure determinations. [SbF₂(NPEt₃)]₂ : Space group Pbca, Z = 8, structure determination with 1264 unique reflections, R₁ = 0.028 for reflections with I > 2σ(I). Lattice dimensions at ?80°C: a = 1284.8, b = 1162.4, c = 1380.4 pm. The compound forms centrosymmetric dimeric molecules, in which the Ψ-trigonal-bipyramidal coordinated antimony atoms are linked via μ₂-N bridges of the NPEt₃^? ligands. [SbF(NPEt₃)₂]₂ : Space group P2₁/c, Z = 4, structure determination with 2270 unique reflections, R₁ = 0.029 for reflections with I > 2μ(I). Lattice dimensions at ?75°C: a = 815.8, b = 1121.2, c = 2068.5 pm, β = 101.09°. The compound forms centrosymmetric dimeric molecules, in which the Ψ-trigonal-bipyramidal coordinated antimony atoms are linked via μ₂-N bridges of one of the two NPEt₃^? ligands. The other NPEt₃^? group is terminally connected. NMe₄⁺SbF₄^? : Space group P2₁/c, Z = 4, structure determination with 1503 unique reflections, R₁ = 0.069 for reflections with I > 2μ(I). Lattice dimensions at ?50°C: a = 539.80, b = 896.10, c = 1760.3 pm, β = 90.338°. The compound includes monomeric SbF₄^? ions with distorted Ψ-trigonal-bipyramidal environment of the antimony atoms.     

Synthese und Kristallstruktur des Kalium‐Iminophosphanids [K4(THF)3(Me3SiNPEt2)2(OSiMe2OSiMe2O)]2

The potassium iminophosphanide complex [K₄(thf)₃(Me₃SiNPEt₂)₂(OSiMe₂OSiMe₂O)]₂ has been obtained by a melt reaction of Me₃SiNPEt₃ with potassium hydride at 140 °C in the presence of silicon grease (—OSiMe₂—)_n and subsequent crystallization from thf solution. The colourless moisture sensitive single crystals are characterized by X‐ray diffraction: Space group P1¯, Z = 1, lattice dimensions at —70 °C: a = 1135.9(3), b = 1250.0(3), c = 1866.1(4) pm, α = 92.65(1)°, β = 100.80(1)°, γ = 93.57(1)°, R₁ = 0.0604. The centrosymmetric dimeric cluster aggregate is formed by two of the eight potassium ions which are connected with the central oxygen atom of both the (OSiMe₂OSiMe₂O)^2— chains as well as with one of their terminal O atoms each. The remaining potassium ions are connected with the phosphorus atoms of the iminophosphanide groups (Me₃SiNPEt₂)^— as well as with its nitrogen atoms. They are terminally solvated by thf molecules.     

A new model to study the phase transition from microstructures to nanostructures in ionic/ionic surfactants mixture

The phase behavior and aggregate structures of mixtures of the oppositely charged surfactants cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) are explored at high dilution by pulsed field gradient stimulated echo (PFG-STE) NMR. The aggregation numbers and hydrodynamic radii of vesicles and mixed micelles were determined by a combination of viscosity and self-diffusion coefficient measurements. The average size of the mixed micelles was larger than that of micelles containing uniformly charged head groups. Analysis of the variations of the self-diffusion coefficient and viscosity with changing concentration of CTAB or SDS in the cationic-rich and anionic-rich regions revealed a phase transition from vesicles to mixed micelles. Differences in the lengths of the CTAB and SDS hydrophobic chains stabilize vesicles relative to other microstructures (e.g., liquid crystalline and precipitate phase), and vesicles form spontaneously over a wide range of compositions in both cationic-rich and anionic-rich solutions. The results obtained from conductometry measurements confirmed this transition. Finally, according to the capacitor model, a new model was developed for estimating the surface potentials and electrostatic free energy (g(elec)). Then we investigated the variations of electrostatic and transfer free energy in phase transition between mixed micelle and vesicle.     

Development of a stability-indicating CE assay for the determination of amlodipine enantiomers in commercial tablets

A simple, accurate, precise and sensitive method using CD for separation and stability indicating assay of enantiomers of amlodipine in the commercial tablets has been established. Several types of CD were evaluated and best results were obtained using a fused-silica capillary with phosphate running buffer (100 mM, pH 3.0) containing 5 mM hydroxypropyl-alpha-CD. The method has shown adequate separation for amlodipine enantiomers from its degradation products. The drug was subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. The range of quantitation for both enantiomers was 5-150 microg/mL. Intra- and inter-day RSD (n=6) was <4%. The limit of quantification that produced the requisite precision and accuracy was found to be 5 microg/mL for both enantiomers. The LOD for both enantiomers was found to be 0.5 microg/mL. Degradation products produced as a result of stress studies did not interfere with the detection of enantiomers and the assay can thus be considered stability indicating.     

Non-covalent intermolecular interactions of colloidal nematic liquid crystals doped with graphene oxide

Graphene oxide (GO) was doped to eutectic uniaxial nematic liquid crystals (NLCs) (E_5CN7) with different percentages to improve the physiochemical properties of NLCs effectively. GO shifts the N-I phase transition temperature to higher values. It has been observed that increasing GO concentration up to 0.75% increases the N-I phase transition temperature substantially while further increase of GO concentration results in an inverse trend. The GO/E_5CN7 non-covalent interactions change the N-I phase transition. The contribution of several terms such as anchoring and polarisation effects on N-I phase transition was quantified as well. The results suggest that the size is an important contributor to GO and liquid crystal interaction. The results show that E_5CN7@GO composites may act as promising candidates to enhance the efficiency of room temperature devices.     

Die Kristallstrukturen von [Et3PNAsPh3]2[Ag2Br4] und [Et3PNAsPh3]2[Pd2Br6]

Crystal Structures of [Et₃PNAsPh₃]₂[Ag₂Br₄] and [Et₃PNAsPh₃]₂[Pd₂Br₆] Colourless single crystals of [Et₃PNAsPh₃]₂[Ag₂Br₄]( 1 ) and red single crystals of [Et₃PNAsPh₃]₂[Pd₂Br₆]( 2 ) have been isolated from saturated solutions in acetonitrile of equivalent mixtures of [Et₃PNAsPh₃]Br with AgBr and PdBr₂, respectively. Both complexes were characterized by IR spectroscopy and by crystal structure determinations. 1 : Space group P1¯, Z = 1, lattice dimensions at ‐70°C: a = 985.0(2), b = 1042.2(5), c = 1345.8(5) pm, α = 102.88(2)°, β = 105.73(2)°, γ = 94.94(2)°, R₁ = 0.0577. 2 : Space group P2₁/c, Z = 2, lattice dimension at ‐70°C: a = 1003.0(1), b = 1371.8(2), c = 1974.0(1) pm, β = 93.30(1)°, R₁ = 0.0458. The dimeric anions of 1 and 2 form planar, centrosymmetric complex units.     

Synthese und Kristallstruktur von [KNPPh3]6 · 4 C7H8

Synthesis and Crystal Structure of [KNPPh₃]₆ · 4 C₇H₈ [KNPPh₃]₆ · 4 C₇H₈ ( 1 ) has been prepared from HNPPh₃ and potassium hydride in boiling toluene forming pale yellow moisture sensitive crystals, which were characterized by a crystal structure determination. Space group P1, Z = 2, lattice dimensions at –83 °C: a = 1517.9(2), b = 1894.0(2), c = 2150,4(2) pm, α = 84.39(1)°, b = 89.31(1)°, c = 89.97(1)°, R₁ = 0.0684. 1 forms a K₆N₆ skeleton of a double cube with a common face of two K and two N atoms, the latter being fivefold coordinated by four K atoms and the P atom of the PPh₃ groups.     

Asymmetrisch substituierte Iminiumsalze [Et3PNAsPh3]X und ihre Reaktion mit Acetonitril. Kristallstrukturen von [Et3PNAsPh3]X (X = Cl,Br), [(Ph3As)2CCN]Br und [(Ph3As)2CCN(SnBr5)]

Asymmetrically Substituted Iminium Salts [Et₃PNAsPh₃]X and their Reactions with Acetonitrile. Crystal Structures of [Et₃PNAsPh₃]X (X = Cl, Br), [(Ph₃As)₂CCN]Br, and [(Ph₃As)₂CCN(SnBr₅)] The asymmetrically substituted iminium salts [Et₃PNAsPh₃]X with X = Cl, Br are formed in the reaction of Me₃SiNPEt₃ with Ph₃AsX₂ at 180 °C in the melt. The products crystallize from acetonitrile as colourless, moisture-sensitive crystals, which crystallize isotypicly in the space group P2₁/c with four formula units in the unit cell. In the cations short PN distances of 159.7 pm and short AsN distances of 172.7 pm are to be found along with PNAs bond angles of 135.8°. With acetonitrile they react in the presence of potassium hydride forming the acetonitrile derivatives [(Ph₃As)₂CCN]X. The crystal structure analysis of the bromide shows an ionic structure with a linear CCN group of the cation and an As–C–As bond angle of 126.9°. [(Ph₃As)₂CCN]Br reacts with tin tetrabromide to form the complex [(Ph₃As)₂CCN(SnBr₅)] with a zwitterionic structure and a bond angle CNSn of 144.0°.     

Synthesis of 1,2,3 triazole-linked pyrimidines catalyzed by mg-Al-LDH-immobilized-CuI as a heterogeneous catalyst

A useful and efficient procedure was obtained for the synthesis of 1,2,3-triazole-linked pyrimidines via click reaction of propynylated pyrimidine and aromatic azides in the presence of Mg-Al-LDH-immobilized-CuI with high-to-excellent yields. Moreover, the prepared catalyst was characterized by the FT-IR spectroscopy, XRD, BET, SEM, and ICP techniques. The developed synthetic technique offers numerous advantages such as a clean reaction, easy workup, high reaction yields, and short reaction time.