Rhenium Products Research Articles

Electrodeposition of rhenium from chloride melts: Electrochemical nature, structure and applied aspects

Processes involved in the electrodeposition of rhenium from chloride melts have been studied over the temperature interval from 680 to 970 0C at a cathodic current density of 5 to 250 mA/cm2. It has been found that rhenium is deposited in the form of continuous layers. In addition to that the growth of deposits as separate single-crystal needles has also been noticed. Continuous layers had axial growth textures. The crystallographic direction of the textures is due to electrolysis conditions, such as concentration of oxygen-containing impurities, temperature, melt composition and cathodic current density. When the concentration of oxygen-containing impurities in the melt decreased, electrolysis temperature increased, the average radius of the supporting electrolyte cations became smaller, or cathodic current density diminished, the direction of the growth textures was changing as follows: (1010) ?(1120) ?(101L) ?(0001) ?(0001)needles. The microhardness of the deposits in this series is 900 to 250 kg/mm2. The growth of deposits on textured rhenium substrates and single crystals having different orientations, including bent substrates, was studied. It has been found that the epitaxial growth is virtually unlimited in depth if the orientation of the substrate coincides with the growth texture under given conditions. If the substrate orientation deviated from the growth texture, the epitaxial growth was nearly absent. Kinetic parameters were measured using the galvanostatic method. The exchange current density was determined over the interval of (0.01-0.1) A/cm2 depending on the concentration of oxygen-containing impurities, cation composition, type of the surface and its condition. The parameter ??Z, which was estimated by two methods, was equal to 2.1-3.1. The diffusion coefficient of rhenium ions has been found to be 2.8 ?10 ?5 cm2/s at 790 0C and 3.5 ?10 ?5 cm2/s at 840 0C. Galvanoplastic production of rhenium products, such as crucibles, ampoules foils, wire, and intricate articles, was performed.

Reactions of dithiolate ligands in mononuclear complexes of rhenium(V).

The thermal reactions of the Re(V) dithiolate complex Cp'ReCl2(SCH2CH2S), 1 (where Cp' = EtMe4C5), and related derivatives have been studied. When 1 is heated in toluene in a sealed evacuated tube at 100 degrees C, a dehydrogenation reaction occurs to form a new rhenium complex with a dithiolene ligand, Cp'ReCl2(SCHCHS), 6, in ca. 40% yield. The structure of 6 has been confirmed by an X-ray diffraction study. Under the thermal conditions studied, 1 also undergoes an olefin extrusion reaction. Free ethene is detected in the NMR spectrum of the products, and insoluble rhenium products are also formed. When 1 is reacted with excess ethene under mild conditions, a new organic product, 1,4-dithiane, is formed. Complex 1 is also found to react with oxidants, such as O2 and S8, under mild conditions to form the dehydrogenation product 6. Kinetic studies of the thermal reaction of 1 and related derivatives have been completed, and possible mechanisms for the thermally induced dehydrogenation reaction are discussed.

Integrated Technology for Processing Rhenium-containing Molybdenite Concentrates to Recover Molybdenum and Rhenium into Commercial Products

The paper reports on processing of molybdenite concentrate to recover molybdenum and rhenium products. The process involves roasting of molybdenite in a fluid bed. The fluid bed exhaust is passed through a cyclone, a electrostatic separator and finally subjected to wet gas scrubbing. The scrub is sent to solid ion exchange resin to produce ammonium perrhenate. The cinder from fluid bed roaster is processed to calcium molybdate and the dust from dust recovery is processed to ammonium paramolybdate.

Integrated Technology for Processing Rhenium-containing Molybdenite Concentrates to Recover Molybdenum and Rhenium into Commercial Products

The paper reports on processing of molybdenite concentrate to recover molybdenum and rhenium products. The process involves roasting of molybdenite in a fluid bed. The fluid bed exhaust is passed through a cyclone, a electrostatic separator and finally subjected to wet gas scrubbing. The scrub is sent to solid ion exchange resin to produce ammonium perrhenate. The cinder from fluid bed roaster is processed to calcium molybdate and the dust from dust recovery is processed to ammonium paramolybdate.

Synthesis, structure and reactivity of [ReH 2(NR) (Cyttp)] + (Cyttp = PhP(CH 2CH 2CH 2PCy 2) 2) complexes. Organoimido analogues of the oxo complex that transfers the elements of water to substrates

The cationic organoimido-hydrido complexes [ReH 2(NR)(Cyttp)] + where R=NC 6H 4Me- p ( 2), Ph ( 3), Cy ( 4) and Cyttp = Php(CH 2CH 2CH 2PCy 2) 2 were synthesized by reaction of [ReH 2(O) (Cyttp) ]O 3SCF 3 ( 1(Tf)) with the appropriate primary amine. Use of molecular sieves promotes the formation of these rhenium products. 2–4 were shown by 1H NMR spectroscopy to contain two inequivalent, cis hydride ligands. An X-ray diffraction study of 2(PF 6) revealed the presence of distorted mer-Cyttp and the organoimido ligand cis to all three phosphorus atoms. The hydrido ligands were not located. Unlike its oxo-hydrido analogue, 1(SbF 6), 2(Tf) failed to react with CO or SO 2 under comparable, or even more forcing, conditions. However, with anhydrous HCl it afforded ReCl 3(Cyttp), and with NaBH 4, ReH 5(Cyttp).

New mechanistic probes of hydride abstraction from rhenium-alkyl complexes (.eta.5-C5H5)Re(NO)(PPh3)(R) by Ph3C+ PF6-. Evidence for initial electron transfer

The mechanism of hydride abstraction from rhenium-alkyl complexes R-(Re) ((Re) = (eta/sup 5/-C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)) by Ph/sub 3/C/sup +/PF/sub 6//sup -/ is probed by study of the equilibrium R-(Re) + Ph/sub 3/C/sup +/ in equilibrium R-(Re)/sup .+/ (eq v) and the effect of oxygen on the rate and deuterium kinetic isotope effect. Equilibrium constants K/sub 5/ are determined in CH/sub 2/Cl/sub 2/ at 208 K from reversible potential measurement for R = PhCH/sub 2/ (1, 2.5 x 10/sup -5/), (CH/sub 3/)/sub 2/CHCH/sub 2/ (2, 7.9 x 10/sup -3/), and Ph(CH/sub 3/)CH (3, 5.0 x 10/sup -2/). When generated electrochemically in separate experiments, R-(Re)/sup .+/ and Ph/sub 3/C/sup ./ are stable under the reaction conditions. Upon mixing CH/sub 2/Cl/sub 2/ solutions of the reactants in (v), rapid reactions ensue giving Ph/sub 3/CH and hydride abstraction products derived from R-(Re). Nearly diffusion controlled rate constants are found for the reaction between Ph/sub 3/C/sup ./ and O/sub 2/. Rate enhancements of ca. an order of magnitude are observed when reactions are carried out in the presence of oxygen, while the rhenium products are essentially unchanged. A deuterium kinetic isotope effect, k/sub H//k/sub D/ = 5.4, is found for reactions of PhCH/sub 2/-(Re)more » and PhCD/sub 2/-(Re) under nitrogen but not in the presence of oxygen. In the presence of O/sub 2/, as much as 70% of the organic product is benzophenone, arising from decomposition of Ph/sub 3/COOH.« less