Crystal Structure of Cis-Dichloro-Bis-{[2-(Diphenylphosphino-κ-P) Methyl]Diphenylphosphine Oxide}Palladium(II) Ethanol Solvate

Abstract  

The title compound cis-Cl₂Pd [P(Ph)₂PCH₂P(O)Ph₂]₂ crystallizes in the monoclinic space group, P2₁/c with crystal cell parameters a = 13.076(5) ?, b = 12.931(5) ?, c = 27.465(9) ?, β = 92.661(6)^o, V = 4639(3) ?³, Z = 4. The bulk of the phenyl groups prohibits the molecule from assuming a conformation that would permit both P=O groups to coordinate another metal ion.     

Origins of thermodynamically stable superhydrophobicity of boron nitride nanotubes coatings

Superhydrophobic surfaces are attractive as self-cleaning protective coatings in harsh environments with extreme temperatures and pH levels. Hexagonal phase boron nitride (h-BN) films are promising protective coatings due to their extraordinary chemical and thermal stability. However, their high surface energy makes them hydrophilic and thus not applicable as water repelling coatings. Our recent discovery on the superhydrophobicity of boron nitride nanotubes (BNNTs) is thus contradicting with the fact that BN materials would not be hydrophobic. To resolve this contradiction, we have investigated BNNT coatings by time-dependent contact angle measurement, thermogravimetry, IR spectroscopy, and electron microscopy. We found that the wettability of BNNTs is determined by the packing density, orientation, length of nanotubes, and the environmental condition. The origins of superhydrophobicity of these BNNT coatings are identified as (1) surface morphology and (2) hydrocarbon adsorbates on BNNTs. Hydrocarbon molecules adsorb spontaneously on the curved surfaces of nanotubes more intensively than on flat surfaces of BN films. This means the surface energy of BNNTs was enhanced by their large curvatures and thus increased the affinity of BNNTs to adsorb airborne molecules, which in turn would reduce the surface energy of BNNTs and make them hydrophobic. Our study revealed that both high-temperature and UV-ozone treatments can remove these adsorbates and lead to restitution of hydrophilic BN surface. However, nanotubes have a unique capability in building a hydrophobic layer of adsorbates after a few hours of exposure to ambient air.     

Synthesis and characterization of poly(pyrazolyl)borate tantalum amide complexes and their reactivities toward oxygen

Reaction of TaCl(NMe2)4 (1) with KTp* [Tp* = tris(3,5-dimethylpyrazolyl)borohydride] yields two products: Tp*Ta(NMe2)4 (2), in which one N atom of the Tp* ligand binds to Ta, and [Tp*Ta(NMe2)4]· 2KTp* (3) where three N atoms of the Tp* ligand in [Tp*Ta(NMe2)4] (2a) bind to Ta. Addition of excess 1 to 3 did not exclude KTp*. Further reaction of 2 with oxygen affords Tp*BH(NMe2) (4). TpTa(NMe2)4 (5) has been synthesized by a similar procedure through the reaction of 1 with TpK [Tp = tris(pyrazolyl)borohydride...     

Trigonal bi- and monopyramidal cobalt(II) complexes of a novel guanidine-based tripodal ligand

The novel ligand DIG(3)tren has three N',N'-diisopropylguanidinyl (DIG) moieties. We report on the structures of two cobalt complexes that show how an isopropylamino group from each DIG acts as a flap that can either close over the metal or rotate away from the metal to open up a site for auxiliary ligand binding. Two of the -NH(iPr) flaps are open in pink [Co(DIG(3)tren)(OAc)]OAc (1), and each of these flaps provides a hydrogen bond to stabilize acetate binding to trigonal bipyrimidal cobalt. The flaps are closed in blue [Co(DIG(3)tren)][BPh(4)](2) (2), yielding a rare example of a trigonal (mono)pyramidal [ML](2+) ion.     

Synthesis and Structure of bis(β-Diketiminate) Chromium(II) Complexes

Abstract  

The new ligand 2,4-N,N′-bis(napthylamino)-pent-2-ene (L^napth) (1) has been synthesized and crystallizes in space group P2₁2₁2₁ with crystal cell parameters a = 8.196(3) ?, b = 9.119(3) ?, c = 25.746(10) ?, V = 1924.3(12) ?³ and Z = 4. The complexes bis[2,4-pentane-N,N′-bis(napthyl)ketiminato] chromium(II) (2), bis[2,4-pentane-N,N′-bis(isopropylphenyl)ketiminato] chromium(II) (3), and bis[2,4-pentane-N,N′-bis(tertbutylphenyl)ketiminato] chromium(II) (4) were synthesized and structurally characterized. Complex 2, the first complex reported with a bis(napthyl) β-diketiminate ligand, crystallizes in space group P − 1 with crystal cell parameters a = 12.0824(15) ?, b = 12.2462(16) ?, c = 14.8975(19) ?, α = 87.035(2)°, β = 80.615(2)°, γ = 62.756(2)°, V = 1932.9(4) ?³ and Z = 2. Complex 3 crystallizes in space group P2₁/n with crystal cell parameters a = 13.088(3) ?, b = 22.222(5) ?, c = 14.206(3) ?, β = 102.310(4)°, V = 4036.6(17) ?³ and Z = 4. Complex 4 crystallizes in space group P2₁/n with crystal cell parameters a = 20.831(6) ?, b = 11.575(4) ?, c = 21.373(7) ?, β = 107.241(5)°, V = 4922(3) ?³ and Z = 4. The degree of twist between the ligand planes is dependent on the steric bulk of the ligand.     

Crystal Structure of [Me2NCH(O)]2Mg[(μ-OPri)2Al(OPri)2]2

Abstract  

Magnesium aluminum isopropoxide coordinates two solvent molecules when crystallized from dimethylformamide yielding the title compound, [Me₂NCH(O)]₂Mg[(μ-OPr ⁱ )₂Al(OPr ⁱ )₂]₂, a potential CVD and sol–gel precursor of spinel, MgAl₂O₄: monoclinic, P2₁/c, a = 18.876(3) ?, b = 12.5225(19) ?, c = 18.578(3) ?, β = 108.333(2)°, V = 4168.6(11) ?³, Z = 4, Mg[(μ-OPr ⁱ )₂Al(OPr ⁱ )₂]₂.     

A new xanthone from Garcinia nitida

A detailed chemical study on the stem bark of Garcinia nitida has led to the isolation of five xanthones. They are 1,6-dihydroxy-5-methoxy-6,6-dimethylpyrano[2',3':2,3]-xanthone (1), inophyllin B (2), osajaxanthone (3), 3-isomangostin (4) and rubraxanthone (5). The structures of these compounds were established using mainly 1-D and 2-D NMR spectroscopy ((1)H, (13)C, DEPT, COSY, HMBC and HMQC) while molecular masses were determined via MS techniques; 1 is a new compound.     

Effect of ambient gas species on the formation of Cu nanoparticles in wire explosion process

In this paper, the effect of ambient gas species on the characteristics of the produced nanoparticles in wire explosion process is reported. Cu wires with a diameter of 125 μm and length of 6.1 cm were exploded in different ambiances of Ar and admixtures of Ar and N₂ at 500 mbar pressure. Immediate formation of arc plasma is observed for Ar ambiance. On the other hand, considerable delay in formation of arc plasma is observed for the admixtures of Ar and N₂. The arc plasma formation time is found to increase with increasing N₂ concentration in the admixture. Transmission electron microscope and X-ray diffraction were used to characterize the produced nanoparticles. Among the nanoparticles produced in different ambient gas species, the nanoparticles produced in Ar ambiance have higher particle size compared to admixtures of Ar and N₂. The particle size is found to reduce with increasing N₂ concentration in the ambiance. Difference in arc plasma formation time is probably the factor that gives rise to the difference in the particle sizes.     

A level-set method for convective–diffusive particle deposition

This article presents a fixed-mesh approach to model convective–diffusive particle deposition onto surfaces. The deposition occurring at the depositing front is modeled as a first order reaction. The evolving depositing front is captured implicitly using the level-set method. Within the level-set formulation, the particle consumed during the deposition process is accounted for via a volumetric sink term in the species conservation equation for the particles. Fluid flow is modeled using the incompressible Navier–Stokes equations. The presented approach is implemented within the framework of a finite volume method. Validations are made against solutions of the total concentration approach for one- and two-dimensional depositions with and without convective effect. The presented approach is then employed to investigate deposition on single- and multi-tube arrays in a cross-flow configuration.     

Mechanistic study of the spiroindolones: a new class of antimalarials

During the synthesis of the new antimalarial drug candidate NITD609, a high degree of diastereoselectivity was observed in the Pictet-Spengler reaction. By isolating both the 4E and 4Z imine intermediates, a systematic mechanistic study of the reaction under both kinetic and thermodynamic conditions was conducted. This study provides insight into the source of the diastereoselectivity for this important class of compounds.