The crystal and molecular structure of trans-tetracarbonylbis(triphenyl-phosphine)chromium(0) in a new unit cell: Is the trans conformer more stable than the cis?

The crystal and molecular structure of trans-Cr(CO)₄(PPh₃)₂ has been determined by single crystal X-ray diffraction. The structure differs from one previously reported, packing in a different unit cell with no molecular center of symmetry. This asymmetry, coupled with the noncoplanarity of the four equatorial carbonyl ligands indicates that the structure is dominated by steric interactions. In spite of this, density functional calculations oncis-M(CO)₄(PPh₃)₂ vs. trans-M(CO)₄(PPh₃)₂, M = Cr, Mo, and W, predict that the gas phase cis conformer is more stable than the trans conformer for all three metals. The complex crystallizes in the triclinic space group with lattice parameters a = 10.139(5) Å, b = 10.583(5) Å, c =17.911(5) Å, = 75.860(5)°, = 77.410(5)°, = 65.930(5)°, V =1686.3(12) ų, Z =2.     

Synthesis and X-ray structure of [(μ-H)Ru3(CO)8(μ-Cl)(μ-dppm)] [dppm = bis(diphenylphosphino)methane]

The reaction of [Ru₃(CO)₁₀(-dppm)] 1 with PPhCl₂ in refluxing CHCl₃ results in the isolation of [(-H)Ru₃(CO)₈(-Cl)(-dppm)] 3 in 10% yield. Compound 3, which has been structurally characterized by crystallographic methods, is also formed from the reaction of 1 with H₂ in refluxing CCl₄. The compound crystallizes in the monoclinic space group P2₁/c with a = 16.814(2), b = 18.7590(12), c = 11.486(2) Å, = 97.745(11)°, V = 3589.8(8) ų, and Z = 4. The hydride and chloride ligands bridge the same edge of the triruthenium cluster as the dppm ligand.     

Aromatic substitution. The effect of alcoholic solvents on the reaction of phenyltriethyltin with mercury (II) salts

Second-order rate constants are reported for the cleavage of the phenyltin bond of phenyltriethyltin by mercury(II) salts in ethanol. propan-1-ol, propan2-ol and butan-1-ol. It is shown that the reactivity order for the mercury(II) salts is HgI₃^? << HgI₂ < HgCl₂. Activation parameters are reported, and on the basis of the low values of activation enthalpies the presence of an intermediate π-complex is suggested for the reactions.     

CeCl3·7H2O: an efficient and reusable catalyst for the preparation of β-acetamido carbonyl compounds by multi-component reactions (MCRs)

A convenient method for the preparation of β-acetamido carbonyl compounds is described by multi-component reactions of aromatic aldehydes, enolizable ketones or β-keto esters and acetonitrile in the presence of acetyl chloride and 10 mol % CeCl₃·7H₂O at room temperature.     

The small signal gain and the saturation intensity measurement of the nitrogen-ion laser

A series oscillator-amplifier has been fabricated and optimized in order to determine the small signal gain and the saturation intensity of the N₂⁺ amplifying medium. Two plasmas, which are composed of a mixture of helium and nitrogen gases, have been produced under pressures of 2–5 atm by applying an electrical transverse discharge. The time delay between the two plasmas has been controlled by the gas pressure. To optimize the gain, the entrance time of the oscillator's output pulse into the amplifier was synchronized with the maximum population inversion in the amplifier. The gain coefficient () was obtained from 6 to 124, by varying the intensity of the input beam at the optimum pressure. The small signal gain and the saturation intensity have been calculated as 0.04, 0.07, 0.10 cm⁻¹ and 7.77, 13.33, 19.97 (kW cm⁻²) at 1.25, 1.70, 2.20 atm, respectively. The dominant wavelength of the nitrogen-ion laser corresponding to the B²∑_u(v = 0) → X²∑_g(v′ = 1) transition, 427.8 (nm) wavelength, was used in this work.     

Spectrophotometric study of the charge-transfer and ion-pair complexation of methamphetamine with some acceptors

The charge-transfer (CT) complexes of methamphetamine (MPA) as a n-donor with several acceptors including bromocresolgreen (BCG), bromocresolpurple (BCP), chlorophenolred (CPR), picric acid (PIC), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been studied spectrophotometrically in chloroform solutions in order to obtain some information about their stoichiometry and stability of complexation. The oscillator strengths, transition dipole moments and resonance energy of the complex in the ground state for all complexes have been calculated. Vertical ionization potential of MPA and electron affinity of acceptors were determined by ab initio calculation. The acceptors were also used to utilize a simple and sensitive extraction-spectrophotometric method for the determination of MPA. The method is based on the formation of 1:1 ion-pair association complexes of MPA with BCG, BCP and PIC in chloroform medium. Beer's plots were obeyed in a general concentration range of 0.24-22 microg ml(-1) for the investigated drug with different acceptors. The proposed methods were applied successfully for the determination of MAP in pure and abuse drug with good accuracy and precision.     

Fluorinated analogs of malachite green: synthesis and toxicity

A series of fluorinated analogs of malachite green (MG) have been synthesized and their toxicity to Saccharomyces cerevisiae and a human ovarian epithelial cell line examined. The toxicity profiles were found to be different for these two species. Two analogs, one with 2,4-difluoro substitution and the other with 2-fluoro substitution seem to be the most promising analogs because they showed the lowest toxicity to the human cells.     

Reactivity of [Re2(CO)8(MeCN)2] with thiazoles: Hydrido bridged dirhenium compounds bearing thiazoles in different coordination modes

Reactions of the labile compound [Re₂(CO)₈(MeCN)₂] with thiazole and 4-methylthiazole in refluxing benzene afforded the new compounds [Re₂(CO)₇{μ-2,3-η²-C₃H(R)NS}{η¹-NC₃H₂(4-R)S}(μ-H)] (1, R = H; 2, R = CH₃), [Re₂(CO)₆{μ-2,3-η²-C₃H(R)NS}{η¹-NC₃H₂(4-R)S}₂(μ-H)] (3, R = H; 4, R = CH₃) and fac-[Re(CO)₃(Cl){η¹-NC₃H₂(4-R)S}₂] (5, R = H; 6, R = CH₃). Compounds 1 and 2 contain two rhenium atoms, one bridging thiazolide ligand, coordinated through the C(2) and N atoms and a η¹-thiazole ligand coordinated through the nitrogen atom to the same Re as the thiazolide nitrogen. Compounds 3 and 4 contain a Re₂(CO)₆ group with one bridging thiazolide ligand coordinated through the C(2) and N atoms and two N-coordinated η¹-thiazole ligands, each coordinated to one Re atom. A hydride ligand, formed by oxidative-addition of C(2)-H bond of the ligand, bridges Re-Re bond opposite the thiazolide ligand in compounds 1-4. Compound 5 contains a single rhenium atom with three carbonyl ligands, two N-coordinated η¹-thiazole ligands and a terminal Cl ligand. Treatment of both 1 and 2 with 5 equiv. of thiazole and 4-methylthiazole in the presence of Me₃NO in refluxing benzene afforded 3 and 4, respectively. Further activation of the coordinated η¹-thiazole ligands in 1-4 is, however, unsuccessful and results only nonspecific decomposition. The single-crystal XRD structures of 1-5 are reported.     

Cycloaddition reactions of phthalimide substituted cyclic polyenes with heteroatom dienophiles

The cycloaddition of 6‐phthalimidobicyclo[5.1.0]octa‐2,4‐diene and 7‐phthalimido‐1,3,5‐cycloheptatriene with nitrosobenzene and with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione each gave a single heterocyclic product. X‐ray crystallographic analysis of 8a indicated the regio‐ and stereoselectivity of this cycloaddition.     

Effective ultrasound-assisted removal of heavy metal ions As(III), Hg(II), and Pb(II) from aqueous solution by new MgO/CuO and MgO/MnO<Subscript>2</Subscript> nanocomposites

A series of new (MgO) _x CuO and (MgO) _x MnO₂ nanocomposites were prepared and used as adsorbent for removal of As³⁺, Hg²⁺, and Pb²⁺ ions from aqueous solution with high capacity and detection limit. These nanocomposites were synthesized with different molar ratios by sonochemical method in alkaline solution using polyvinylpyrrolidone as a capping agent and were characterized by FTIR, AAS, UV–Vis spectroscopy, and TEM and SEM imaging. The maximum heavy metal ions adsorption was achieved for (MgO)_0.32CuO and (MgO)_2.9MnO₂ nanocomposites assisted by 3-min sonication using ultrasound. Adsorbent capacity of (MgO)_0.32CuO reached 500.0 mg/g and detection limit was 0.1 ppb for As³⁺. Also (MgO)_2.9MnO₂ nanocomposite adsorbed 457.1 mg/g of Hg²⁺ and 461.2 mg/g of Pb²⁺. Extremely low detection limits of 1.5 and 2.0 ppb were obtained for Hg(II) and Pb(II) ions, respectively, which are much lower than the WHO allowable limits. So, these nanocomposites should be excellent candidate for heavy metal removal with advantage of high capacity, high sensitivity, cost effectiveness and easy preparation.