The synthesis of iron–nickel alloy nanoparticles using a reverse micelle technique

Nanosized Fe_0.2Ni_0.8 particles were prepared by reducing their salts with sodium borohydride (NaBH₄) in cationic water-in-oil (w/o) microemulsions of water/cetyl-trimethyl-amonium bromide (CTAB) and n-butanol/isooctane at 25 °C. According to the TEM and X-ray diffraction analyses, the synthesized particles were around 4–12 nm in size. Due to their nanodimensions, the particles had a primitive cubic (pc) structure rather than the body-centered cubic (BCC) structure of the bulk material. An examination of the synthesis from the reverse micelle reveals that the morphology of the iron–nickel alloy nanoparticles depends mainly on the microemulsion's composition. The magnetization of the nanoparticles was much lower than that of the bulk material, reflecting the influence of the nanodimensions on the particles’ magnetizations.     

Hydrolysis of the Peptide Bond in N-Acetylated L-Methionylglycine Catalyzed by Various Palladium(II) Complexes: Dependence of the Hydrolytic Reactions on the Nature of the Chelate Ligand in cis-[Pd( L)(H 2O) 2] 21 Complexes

Summary. Hydrolytic reactions between various palladium(II) complexes of the type cis-[Pd(L)(H₂O)₂]²⁺ in which L is ethylenediamine (en), 1,2-propylenediamine (1,2-pn), isobutylenediamine (ibn), 1,2-diaminocyclohexane (1,2-dach), N-methylethylenediamine (Meen), N,N,N,N-tetramethylethylenediamine (Me₄en), S-methyl L-cysteine (MeS-L-HCys), L-methionine (L-HMet), and 2,5-dithiahexane (dth) and dipeptide N-acetylated L-methionylglycine (MeCOMet-Gly) were studied by ¹H NMR spectroscopy. The reactions were carried out in the pH range 2.0–2.5 and at 50°C. In all these reactions, palladium(II) complex bound to a methionine residue effects the regioselective cleavage of the amide bond involving the carboxylic group of methionine. We found that the rate of hydrolysis and mechanism of this reaction are strongly dependent from the nature of the chelate ligand L in palladium(II) complexes of the type cis-[Pd(L)(H₂O)₂]²⁺.     

On a resonance energy model based on expansion in terms of acyclic moments: Exact results

Summary The new concept of the resonance energy in conjugated hydrocarbons introduced by Jiang Y, Zhang H (1989) Theor Chim Acta 75:279 is further developed. This model is based on expansion of the -electron energy in terms of moments which are also equal to numbers of closed walks in a molecular graph. The reference system is established by counting only acyclic walks, i.e. those tracing only on acyclic subgraphs. Because acyclic walks could be counted only up to some finite length, the energy of the reference system has been evaluated by truncating higher terms in the expansion. In this paper a finite expression for the energy of the same reference system is derived, thus allowing its exact evaluation. The exact values differ significantly from the truncated ones. This difference, as well as the discrepancy between exact results and chemical experience, are discussed.     

Distribution of major and trace elements concentrations in gold processing using EDXRF

Studies have been carried out on the distribution of major and trace elements concentrations in oxide and sulphide feed ores at various stages of milling and processing of gold in a goldmine at Bogoso in the western region of Ghana. The studies evaluated concentration enhancements at various stages of treatment with emphasis on understanding the typical processes leading to enhancement of concentration at each stage and ultimately the impact from discharges into the surrounding environment. The feed ore samples were analyzed using energy dispersive X-ray fluorescence spectrometry. The results show concentration enhancements of a significant number of elements at some stages of processing in the two processing plants with the highest number of elements with enhanced concentrations coming from chemically treated media of both plants. Though there are relatively high concentrations of V (max.: 284 ppm), Cr (max.: 149 ppm), Co (max.: 84 ppm), and U (max.: 26.8 ppm) at the discharge points, the concentrations of most of the toxic elements in the slurries discharged into the tailings dam are mostly within their respective world averages. The enrichment indices computed for the slurries being discharged into the tailings dam suggests that the dam is not enriched with the toxic elements Cr, Co, Ni, Zn, Cu and Pb. The enrichment index of the slurries discharged into the tailings dam decreases in the order of oxide plant > sulphide plant. Principal component analyses performed suggest that Al₂O₃, K₂O, Co, Zn, Cu, Y and Zr are geochemically associated. Results from the studies also suggest that the discharge of these elements into the tailings dam may contribute insignificant pollution of the surrounding area.     

Synthesis of Aminobisphosphonate

A new facile synthesis of aminobisphosphonate was reported. Dibenzylamine bisphosphonate (1) is prepared from dibenzylamine, triethyl orthoformate and diethyl phosphite. Deprotection by hydrogen transfer reaction and acid hydrolysis afforded aminobisphosphonate (2).     

Molybdenum(VI) Bis(imido) Complexes: From Frustrated Lewis Pairs to Weakly Coordinating Cations

Molybdenum(VI) bis(imido) complexes [Mo(NtBu)₂(L^R)₂] (R=H 1 a ; R=CF₃ 1 b ) combined with B(C₆F₅)₃ ( 1 a /B(C₆F₅)₃, 1 b /B(C₆F₅)₃) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H−H, Si−H and O−H bonds. Cleavage of H₂ and Et₃SiH affords ion pairs [Mo(NtBu)(NHtBu)(L^R)₂][HB(C₆F₅)₃] (R=H 2 a ; R=CF₃ 2 b ) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H₂O leads to [Mo(NtBu)(NHtBu)(L^R)₂][(HO)B(C₆F₅)₃] (R=H 3 a ; R=CF₃ 3 b ). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a . Mechanistic elucidation revealed insertion of the aldehyde into the B−H bond of [HB(C₆F₅)₃]⁻. We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(L^R)₂][{PhCH₂O}B(C₆F₅)₃] (R=H 4 a ; R=CF₃ 4 b ). Catalysis occurs at [HB(C₆F₅)₃]⁻ while [Mo(NtBu)(NHtBu)(L^R)₂]⁺ (R=H or CF₃) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).