Extractive and sorption preconcentration of rhenium(VII) with the use of phosphoryl-containing podands

Interphase distribution of micro amounts of ReO ₄ ^? between aqueous solutions of mineral acids and solutions of phosphoryl-containing mono-, di-, and tripodands, derived from 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene in dichloroethane was studied. The stoichiometry of extracted complexes was determined, the effect of HNO₃, HCl, and H₂SO₄ concentration in aqueous phase and the nature of organic solvent on the efficiency of transition of ions into organic phase was considered. The growth of the number of phosphoryl groups in podand molecule enhances its extraction ability toward Re(VII). The possibility of selective recovery and preconcentration of Re(VII) with complexing sorbent obtained by noncovalent binding of phosphoryl-containing podand on the surface of macroporous polymer Amberlite XAD7HP was shown.     

Extraction and sorption preconcentration of rhenium with the use of 2-phosphorylphenoxyacetamides

Interfacial distribution of micro amount of ReO₄ ^- between aqueous solutions of mineral acids and solutions of 2-phosphorylphenoxyacetamides in dichloroethane has been studied. Stoichiometry of extracted complexes has been determined; the effect of HNO₃, HCl, and H₂SO₄ concentration in aqueous phase, extractant structure, and organic solvent nature on the efficiency of ReO₄ ^- ions transfer into organic phase has been considered. It has been shown that Re(VII) can be selectively recovered and concentrated with complexing sorbent obtained by the noncovalent binding of 2-[2-(diphenylphosphoryl)-4-ethylphenoxy]-N,N-dioctylacetamide on the surface of macroporous polymer Amberlite XAD7HP.     

Polyhydroxy complexes of rhenium(VII)

Perrhenate in concentrated alkali forms yellow complexes with a number of polyhydric compounds. With d-gluconolactone it was found that this color was due to a considerable broadening of the perrhenate band in the UV. The optical rotation of alkaline d-gluconate changes markedly on adding perrhenate, and increases almost linearly with increasing NaOH concentration from 2–16.8 M. A continuous variations analysis of this complex in 12M NaOH showed that it was a 1:1 compound of gluconate and perrhenate. Its formation constant was approximately 43 LM⁻¹. Ligands which produced a yellow color with perrhenate in 12 M NaOH, and whose optical rotation changed significantly included d-mannitol, d-glucitol (sorbitol), perseitol, arabinitol and sodium d-xylonate. Ligands which did not react with perrhenate were: ethylene glycol, glycerol, ribitol, ribonolactone and d-allonolactone. It was concluded that vicinal OH-bearing carbon atoms with opposing configurations (D-L) are required to form these complexes, and that the distance between the centers of adjacent oxygen atoms in the ligand is critical in determining whether the perrhenate will form a complex. It was further concluded that ligands of this type stabilize some sort of meso-perrhenate anion. Pertechnetate does not form these complexes under the same conditions.     

Extraction of rhenium(VII) by phosphorylated podands

The interphase distribution of ReO ₄ ^- between aqueous H₂SO₄ solutions and solutions of phosphorylated podands in organic solvents is studied. The stoichiometry of extracted complexes is determined. The rhenium extraction efficiency is considered as a function of the structure of the extractant and the nature of the organic solvent.     

Recovery of rhenium(VII) with triisooctylamine from sulfuric acid solutions

Extraction recovery of rhenium(VII) with triisooctylamine from model sulfuric acid solutions was studied. The effect of the composition of the organic and aqueous phases on the recovery of rhenium(VII) was analyzed, and the composition of rhenium(VII) complexes in the organic phase was determined. The possibility of effective re-extraction of rhenium(VII) from triisooctylamine with ammonia solutions was demonstrated.     

Extraction of rhenium(VII) with aliphatic alcohols from acid solutions

Extraction of rhenium(VII) with C₇–C₁₀ aliphatic alcohols from HCl and H₂SO₄ solutions was examined. The rhenium(VII) distribution coefficients were examined in relation to the acidity and temperature. The composition of the extracted complexes and the thermodynamic parameters of extraction were determined. The extraction method of recovery and preconcentration of rhenium(VII) from H₂SO₄ solutions with secondary octyl alcohol was tested in the counterflow mode.     

Radiochemical separation of rhenium(VII) from tungsten(VI)

The absorption of rhenium(VII) and tungsten(VI) ions on Al₂O₃ from HCl, HClO₄, HNO₃, H₂SO₄, H₃PO₄, NaOH, NH₄OH, NaCl, NaF, and Na-tartarate solutions by batch equilibration, as well as by passage through a chromatographic column, has been studied. The results show that rhenium(VII) can be effectively separated from tungsten(VI) using any of the acid or salt solutions investigated. The experimental data allowed to develop a simple procedure for the radiochemical separation of rhenium isotopes from an irradiated WO₃ sample.     

The efficacy of nitrosonaphthol functionalized XAD-16 resin for the preconcentration/sorption of Ni(II) and Cu(II) ions

Amberlite XAD-16 resin has been functionalized using nitrosonaphthol as a ligand and characterized employing elemental, thermogravimetric analysis and FT-IR spectroscopy. The sorption of Ni(II) and Cu(II) ions onto this functionalized resin is investigated and optimized with respect to the sorptive medium (pH), shaking speed and equilibration time between liquid and solid phases. The monitoring of the influence of diverse ions on the sorption of metal ions has revealed that phosphate, bicarbonate and citrate reduce the sorption up to 10–14%. The sorption data followed Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherms. The Freundlich parameters computed are 1/n = 0.56 ± 0.03 and 0.49 ± 0.05, A = 9.54 ± 1.5 and 6.0 ± 0.5 mmol g⁻¹ for Ni(II) and Cu(II) ions, respectively. D–R isotherm yields the values of X_m = 0.87 ± 0.07 and 0.35 ± 0.05 mmol g⁻¹ and of E = 9.5 ± 0.23 and 12.3 ± 0.6 kJ mol⁻¹ for Ni(II) and Cu(II) ions, respectively. Langmuir characteristic constants estimated are Q = 0.082 ± 0.005 and 0.063 ± 0.003 mmol g⁻¹, b = (4.7 ± 0.2) × 10⁴ and (7.31 ± 0.11) × 10⁴ l mol⁻¹ for Ni(II) and Cu(II) ions, respectively. The variation of sorption with temperature gives thermodynamic quantities of ΔH = −58.9 ± 0.12 and −40.38 ± 0.11 kJ mol⁻¹, ΔS = −183 ± 10 and −130 ± 8 J mol⁻¹ K⁻¹ and ΔG = −4.4 ± 0.09 and −2.06 ± 0.08 kJ mol⁻¹ at 298 K for Ni(II) and Cu(II) ions, respectively. Using kinetic equations, values of intraparticle transport and of first order rate constant have been computed for both the metal ions. The sorption procedure is utilized to preconcentrate these ions prior to their determination in tea, vegetable oil, hydrogenated oil (ghee) and palm oil by atomic absorption spectrometry using direct and standard addition methods.     

Synthesis and molecular structure of chlorotris(trimethylsilylmethyl)trimethylsilyl-methylidyne rhenium(VII)

The complex Re(CSiMe₃)(CH₂SiMe₃)₃Cl has been isolated as yellow crystals in low yield from the reaction of ReCl₄(THF)₂ with Me₃SiCH₂MgCl and characterised by X-ray crystallography. The molecule has a trigonal bipyramidal geometry with the alkylidyne and chlorine ligands axial.     

Hydrogenation of 9-pyridylmethylene- and 9-benzylidene(aza)fluorenes in the presence of rhenium heptasuifide

Hydrogenation of 9-pyridylmethylene(aza)fluorenes and 9-benzylidene-4-azafluorene at 250 °C andp _{H 2} = 130 atm in the presence of Re₂S₇ as a catalyst occurs preferably at the exoeyclic double bond of the fulvene fragment to yield pyridyl-9-(aza)fluorenylmethanes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 180–182, January, 1996.     

N-(4-amino-7-nitrobenzaoxa-1,3-diazole)-substituted aza crown ethers: complexation with alkali, alkaline earth metal ions and ammonium

Three novel aza-crown ether derivatives incorporating 4-amino-7-nitrobenzaoxa-1,3-diazole (NBD) chromophore were synthesized and their structure confirmed by ¹H-NMR, IR and elemental analysis. The influence of the solvent polarity and protonation on the photophysical properties of NBD-15-crown-5 was studied by UV/Vis and fluorescence methods. The influence of the investigated cations on the absorption spectra of the ligands was negligible, however emission was strongly affected. Complexation and binding stability of NBD-aza-15-crown-5 and NBD-aza-18-crown-6 were studied using fluorescence spectroscopy. NBD-aza-18-crown-6 exhibits strong selectivity toward Ca²⁺ and Sr²⁺ ions with formation constants about 10³ times higher than the formation constants with the other ions included in the study.     

Syntheses and structures of lanthanide(III) complexes with some bis(pyrazolyl)borate and tris(pyrazolyl)borate podand ligands

Two new poly(pyrazolyl)borate ligands have been prepared: potassium tris[3-{(4-^tbutyl)-pyrid-2-yl}-pyrazol-1-yl]hydroborate (KTp^BuPy) which has three bidentate arms and is therefore hexadentate; and potassium bis[3-(2-pyridyl)-5-(methoxymethyl)pyrazol-1-yl]-dihydroborate (KBp^(COC)Py) which has two bidentate arms and is therefore tetradentate. The crystal structures of their lanthanide complexes [La(Tp^BuPy)(NO₃)₂] and [La(Bp^(COC)Py)₂X] (X=nitrate or triflate) have been determined. In [La(Tp^BuPy)(NO₃)₂] the metal ion is ten-coordinate, from the hexadentate N-donor podand ligand and two bidentate nitrates. [La(Bp^(COC)Py)₂(NO₃)] is also ten-coordinate, from two tetradentate ligands and a bidentate nitrate, but in [La(Bp^(COC)Py)₂(CF₃SO₃)] the metal ion is nine-coordinate because the triflate anion is monodentate. Two unexpected new complexes which arose from partial decomposition of the poly(pyrazolyl)borate ligands have also been characterised structurally. In [La(^BuPypzH)₃(O₃SCF₃)₃] the metal ion is nine-coordinate from three bidentate pyrazolyl-pyridine arms (liberated by decomposition of KTp^BuPy) and three triflate anions; there is extensive NH· · · O hydrogen-bonding between the pyrazolyl and triflate ligands. [Nd(Tp^Py)(Bp^Py)][Nd(PypzH)(NO₃)₄] was isolated from the reaction of hexadentate tris[3-(2-pyridyl)-pyrazol-1-yl]hydroborate (Tp^Py) with Nd(NO₃)₃. One of the Tp^Py ligands has lost one bidentate pyrazolyl-pyridine ‘arm’ (PypzH) to leave tetradentate tris[3-(2-pyridyl)-pyrazol-1-yl]dihydroborate (Bp^Py). In this structure, the cation [Nd(Tp^Py)(Bp^Py)]⁺ is ten-coordinate from inter-leaved hexadentate and tetradentate ligands, and the anion [Nd(PypzH)(NO₃)₄]⁻ is also ten-coordinate from the bidentate N-donor ligand PypzH and four bidentate nitrates.     

Synthesis and characterization of rhenium(VII) oxide complexes of phenothiazines

Summary Five complexes of rhenium(VII) oxide with N-alkylphenothiazines have been synthesized and characterized on the basis of elemental analyses, molar conductances, and u.v.-vis., i.r. and n.m.r. spectral data. The molecular formulas of the new ionic complexes are: [ReO₃(PTZ)₂(H₂O)][ReO₄], PTZ = chlorpromazine, promethazine or ethopropazine; [ReO₃(TF)(H₂O)][ReO₄], TF = trifluoperazine; and [ReO₃(TR)₃][ReO₄(H₂O)₂]·H₂O, TR = thioridazine. Tentative structures have been proposed.     

Coordination and extraction properties of new bis- and tetrakis(diphenylphosphoryl)-substituted pyrazines towards f-block elements

2,3-Bis- and 2,3,5,6-tetrakis(diphenylphosphoryl)-substituted pyrazines have been synthesized from the corresponding polychloropyrazines and ethyl diphenylphosphinite. They may serve as new N,O-bidentate organophosphorus ligands for extraction and recovery of f-block metal ions from nitric acid solutions.     

Preparation of bis(aryldiazene) and new aryldiazenido complexes of rhenium

Mixed-ligand hydride ReH₂(NO)L(PPh₃)₂ complexes [L=P(OEt)₃ or PPh(OEt)₂] were prepared by allowing the ReH₂(NO)(PPh₃)₃ species to react with an excess of phosphite. Treatment of ReH₂(NO)L(PPh₃)₂ hydrides with an equimolar amount of aryldiazonium cations ArN₂⁺ gives the mono-aryldiazene [ReH(ArNNH)(NO)L(PPh₃)₂]BPh₄ complexes (Ar=C₆H₅, 4-CH₃C₆H₄), while treatment with an excess of ArN₂⁺ yields bis(aryldiazene) [Re(ArNNH)₂(NO)L(PPh₃)₂](BPh₄)₂ derivatives. Binuclear [{ReH(NO)L(PPh₃)₂}₂(μ-HNNArArNNH)](BPh₄)₂ and [{Re(4-CH₃C₆H₄NNH)(NO)L(PPh₃)₂}₂(μ-HNNArArNNH)](BPh₄)₄ complexes (ArAr=4,4′-C₆H₄C₆H₄, 4,4′-C₆H₄CH₂C₆H₄) were also prepared. The reaction of the triphenylphosphine ReH₂(NO)(PPh₃)₃ complex with aryldiazonium cations was studied and led exclusively to mono-aryldiazene [ReH(ArNNH)(NO)(PPh₃)₃]BPh₄ and [{ReH(NO)(PPh₃)₃}₂(μ-HNNArArNNH)](BPh₄)₂ derivatives. The complexes were characterised spectroscopically (IR, NMR) using the ¹⁵N-labelled derivatives. The aryldiazenido [ReH(C₆H₅N₂){PPh(OEt)₂}₄]BPh₄ complex was prepared by allowing trihydride ReH₃[PPh(OEt)₂]₄ to react with phenyldiazonium tetrafluoroborate. A reaction path involving the aryldiazene [ReH₂(C₆H₅NNH){PPh(OEt)₂}₄]⁺ intermediate was also proposed.     

Extraction of rhenium(VII) and molybdenum(VI) with hexabutyltriamide of phosphoric acid from acid media

Extraction of rhenium(VII) and molybdenum(VI) from sulfuric, hydrochloric, and nitric acid solutions with hexabutyltriamide of phosphoric acid was studied. The influence exerted on the extraction of Re(VII) and Mo(VI) by the nature and concentration of an acid in the aqueous phase, temperature, time of contact between phases, and concentration of the extracting agent in the organic phase was analyzed. Isotherms of extraction of rhenium(VII) and molybdenum(VI) with solutions of hexabutyltriamide phosphoric acid in kerosene were obtained, the composition of the complexes being extracted was determined, the enthalpies and entropies were evaluated, and the concentration constants of extraction of the metals were found.