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The crystal structure and vibrational spectra of deuterated pyridinium perrhenate (d 5 PyH)ReO 4 (C 5 D 5 NHReO 4 ) have been studied by means of X-ray diffraction and Raman spectroscopy at high pressures up to 15 and 9.5 GPa, respectively. Two phase transitions, from orthorhombic phase II with Cmc2 1 symmetry to phase I with Cmcm symmetry at P = 0.7 GPa and to new monoclinic phase IV with P2 1 symmetry at P = 5 GPa were observed. The internal vibrational modes frequencies, lattice parameters and unit cell volume as functions of pressure were obtained for different phases.

The reaction of tetraphenylantimony chloride with sodium perrhenate or potassium chlorate yields tetraphenylantimony perrhenate (I) and tetraphenylantimony chlorate (II), respectively. Complex I was also synthesized from pentaphenylantimony and triphenylantimony diperrhenate in toluene. According to X-ray diffraction, crystals I and II consist of almost regular tetrahedral tetraphenylstibonium cations (CSbC, 109.4(2)°–109.5(7)° in I and 109.1(1)°–109.6(1)° in II) and [ReO4]− (OreO, 107.6(3)°–113.3(5)°) and [ClO3]− (OClO, 96.3(9)°, 116.4(5)°) anions, respectively. The average Sb-C bond lengths (2.094(3) A in I, 2.097(2) A in II) are close to the sum of the covalent radii of the Sb and C atoms. The average distances Re-O in complex I (1.672(4) A) and Cl-O in complex II (1.315 A) correspond to multiple bonds.

Two novel and simple methods for post-elution concentration (PEC) of (188)Re-perrhenate, using (i) a single diethyl amino ethyl (DEAE) cellulose anion exchanger column and (ii) a combination of Dowex-1 x 8 and AgCl columns, are described here. In the first system, 20-25 ml of (188)Re-perrhenate in acidic ammonium acetate was trapped in the small anion exchanger column of DEAE cellulose which was subsequently recovered in 4 ml of normal saline. In the second method, (188)Re-perrhenate eluate in 20-40 ml normal saline was trapped on a small strong base anion exchanger column, Dowex-1 x 8, and recovered in 5 ml of 0.2M NaI solution and finally processed over 1g AgCl column so as to obtain it in physiological saline solution in a final volume of 6.5 ml including 1.5 ml de-ionized water washings. In both the methods, the radiochemical purity of (188)Re-perrhenate was98% and (188)W breakthrough was less than 10(-3)%.

The perrhenate anion, ReO 4 - , is taken as a showcase of heavy transition metal complexes, to examine the performance of time-dependent relativistic density functional linear response theory for electronic excitations, which is based on a newly proposed exact two-component Hamiltonian resulting from the symmetrized elimination of the small component. In total 30 scalar and 63 spinor excited states are investigated and the results are grossly in good agreement with those by the singles and doubles coupled-cluster linear response theory. It is found that only a few scalar states of 3T1 and 3T2 symmetries are split significantly by the spin–orbit coupling, whereas only those excited states involving the Rydberg-type virtual orbital are affected by the solvent effects. The nature of the optical absorption spectra is also highlighted.

A procedure is developed for determining rhenium in gold-containing ores by X-ray fluorescence spectrometry. The adsorption preconcentration of perrhenate ions on activated charcoal is studied. It is found that the pH of the solution, the time of exposing the adsorbent to the solution, UV irradiation, and the presence of associate elements (tungsten, gold, silver, and copper) affect the adsorption. The procedure is applied to the X-ray fluorescence determination of rhenium in gold-containing ores from different deposits.

Trimetallic oxoalkoxide complexes (Nb0.7Ta0.3)4O2(OMe)14(ReO4)2 (I), (Nb0.3Ta0.7)4O2(OMe)14(ReO4)2 (II) and (Nb0.5Ta0.5)4O2(OMe)14(ReO4)2 (III) were obtained by the interaction of rhenium heptoxide (VII) Re2O7 with niobium and tantalum alkoxides M2(OMe)10 (M=Nb, Ta) in toluene. The centrosymmetric molecules (I)–(III) can be considered as a product of condensation of two M2(OMe)9(OReO3) molecules with the formation of two oxo-bridges. The specific feature of the structure is the uneven distribution of metal atoms in the crystallographic positions, where one symmetry-independent position, connected via μ-O with a perrhenate ReO4− group, is predominantly occupied by niobium atoms, while the other one connected via alkoxide groups has a higher tantalum content. The distribution of Nb and Ta in the structure is truly even only for compound III. The niobium and tantalum content is varied to a different extent for I (less) and for II (more), which is apparently due to small differences in the sizes of these two cations, resulting in preferences for packing of different molecules in the structures. Thermal decomposition of (Nb1−xTax)4O2(OMe)14(ReO4)2 (x=0.3, 0.5, 0.7) in air leads to the formation of crystalline species of solid solutions based on tantalum and niobium oxides displaying semi-ordered pores with the size of 100−250 nm. In the dry nitrogen atmosphere, the decomposition leads to the amorphous complex oxides containing rhenium, niobium and tantalum.

A semi-automated system has been designed and installed for the routine production of highly concentrated solutions of rhenium-188 perrhenate in saline which incorporates extensive radiation protection for the laboratory staff. This new system represents a simple, rapid, and effective computer controlled method using inexpensive disposable components. The flipper-valve settings and the radioactivity measured by use of collimated gamma dose rate probes are continuously monitored. If necessary, 2-3 tungsten-188/rhenium-188 generators can be eluted in a tandem arrangement. Eluate volumes (1.3-2 ml) of maximum specific radioactivity of 25 GBq/ml were routinely prepared.

Disiloxy, dichloro, dibromo and dithiocyanato molybdenum, tungsten and rhenium-oxo complexes bearing bidendate N-ligands have been synthesized in a one-pot process and fully characterized spectroscopically. The reaction, in acetonitrile, is significantly simpler to run than previously reported methods for the synthesis of analogous compounds and appears to be general in character.

2þ cations. The other four MnO � 4 anions are located in a crystallographically different environment, namely in the cavities formed by the attachment of the building blocks. A low-temperature quasi-intramolecular redox reaction producing NH4NO3 and amorphous ZnMn2O4 could be established occurring even at 1008. Due to H-bonds between the (Zn(NH3)4)2þ cation and the MnOanion, a redox reaction took place between the NH3 and the anion; thus, thermal deammoniation of compound 1 cannot be used to prepare (Zn(NH3)2)(MnO4)2 (contrary to the behavior of the analogous perrhenate (ReO � 4 ) complex). In solution-phase deammoniation, a temperature-dependent hydrolysis process leading to the formation of Zn(OH)2 and NH4MnO4 was observed. Refluxing 1 in toluene offering the heat convecting medium, followed by the removal of NH4NO3 by washing with H2O, proved to be an easy and convenient technique for the synthesis of the amorphous ZnMn2O4.

Heterobimetallic complexes of a vanadium(V) and rhenium(VII) combination connected by a mu-oxido bridge [LVO(mu-O)ReO 3].H 2O [H 2L = N, N'-ethylene bis(salicylideneimine) (H 2salen) and its methoxy derivative] ( 1, 2) are reported. The compounds have been prepared by a single-pot synthesis in which the precursor [V (IV)OL] complexes are allowed to be oxidized aerially in the presence of added perrhenate. The oxidized [V (V)OL] (+) species accommodate the ReO 4 (-) anion in their vacant coordination site, trans to the terminal oxido group, providing the complexes 1 and 2. The later generates a binuclear oxovanadium(V) compound [H 2en][(TBC)VO(mu-TBC) 2OV(TBC)].5H 2O ( 3) when treated with tetrabromocatechol. Single crystal X-ray diffraction analysis and (1)H NMR spectroscopy have been used to establish their identities. In compound 2, the Re(1)-O(11)-V(1) bridge angle is barely linear [170.2(3) degrees ] with a Re...V separation of 3.9647(9) A. The redox behavior of 1 and 2 are quite interesting, each undergoing two reductions both in the positive potential range at E 1/2 = 0.59 (process I) and E 1/2 = 0.16 V (process II) versus Ag/AgCl reference (corresponding potentials are 0.59 and 0.18 V for 2). Process I has a single-electron stoichiometry involving the [VO(salen)] part of the complexes as established by combined coulometry-Electron Paramagnetic Resonance (EPR) experiments which provide an eight-line isotropic EPR pattern at room temperature ( = 1.967; = 87 x 10 (-4) cm (-1)), characteristic of an unpaired electron being coupled to a vanadium nuclear spin ( (51)V, I = 7/2). The almost linear V-O-Re bridge in 1 and 2 allows this unpaired electron to interact effectively with the neighboring Re nuclear spin, leading to familiar " two-line pattern" superhyperfine coupling ( A ( (185,187)Re) = 20.7 x 10 (-4) cm (-1)). Process II, on the other hand, is based on a Re(VII/VI) electron transfer as confirmed by differential pulse and normal pulse voltammetric experiments.

The coordination complexes of trivalent f-element pertechnetates and perrhenates with some N-donor ligands were determined by using X-ray structural analysis: Nd3+ perrhenate with 2,6-bis(tetramethylfurano)-1,2,4-triazin-3-yl)-pyridine ([Nd(FBTP)3ReO4](ReO4)2 · 2H2O (I)), tris(2-pyridylmethyl)amine ([Nd(TPA)(ReO4)3] (II)) and N,N′-tetraethylmalonamide ([Nd(TEMA)4](ReO4)3 (III)). The coordination number of Nd is 10 in I, 9 in II and 8 in III. The complexes of Nd3+ pertechnetate and Am3+ pertechnetate with TPA have been also synthesized (Nd(TPA)(TcO4)3 (IV) and Am(TPA)(TcO4)3 (V)). The structure II does not change on replacement of perrhenate by pertechnetate and neodymium by americium.

This work describes the installation, use, and quality control (QC) of the alumina-based tungsten-188 ((188)W)/rhenium-188 ((188)Re) generators provided by the Oak Ridge National Laboratory (ORNL). In addition, methods used for concentration of the (188)Re-perrhenate bolus and preparation of (188)Re-labeled HDD (4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol) for trans-arterial administration for therapy of nonresectable liver cancer also are described. The (188)W/(188)Re generator has a long useful shelf-life of several months and is a convenient on-site (188)Re production system. (188)Re has excellent therapeutic and imaging properties (T(1/2) 16.9 hours; E(betamax) 2.12 MeV; 155-keV gamma ray, 15%) and is cost effectively obtained on demand by saline elution of the generator. The clinical efficacy of a variety of (188)Re-labeled agents has been demonstrated for several therapeutic applications. Because of the favorable physical properties of (188)Re, several (188)Re-labeled agents are being developed and evaluated for the treatment of nonresectable/refractory liver cancer. (188)Re-labeled HDD has been the most widely studied of these agents for this application and has been introduced into clinical trials at a number of institutions. The trans-arterial administration of (188)Re-labeled agents for treatment of inoperable liver cancer requires use of high-level (1-2 Ci) (188)W/(188)Re generators. The handling of such high levels of (188)Re imposes radiological precautions normally not encountered in a radiopharmacy and adequate care and ALARA (ie, "As Low As Reasonably Achievable") principles must be followed. The ORNL generator provides consistently high (188)Re yields (>75%) and low (188)W parent breakthrough (

Three Zn(II)4L4 coordination cages, assembled from trisiminopyridine ligands, exhibit differences in their guest-binding selectivities and reactivity with tris(2-aminoethyl)amine (tren), which enabled the design of a molecular network that responded in distinct ways to different chemical signals. When two of these cages were present in solution together, one of them was observed to selectively encapsulate chloroform, and the other was observed to selectively encapsulate cyclohexane. The two guests could be released sequentially, in a specified order defined by the input of two separate chemical signals: tren and perrhenate. Furthermore, the observed reactivity of tren with the initial cage mixture provided control over the uptake and release of perrhenate within the third cage formed in situ. One of these tetrahedral cages has been identified as a tight (K(a) > 10(7) M(-1)) and selective host for perrhenate, an anion of great physicochemical similarity to pertechnetate, both having uses in nuclear medicine.

SSCI-VIDE+ECI2D+GAN; International audience; In the current study, a new approach to the synthesis of highly destacked ReS2 layers embedded in amorphous carbon via the thermal decomposition of a tetraoctylammonium perrhenate precursor, under sulfidizing atmosphere (15% v/v H2S mixture H2S/H-2 gas), is described. X-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analysis of the thermolysis product confirm the formation of rhenium disulfide. The synthesized compound is found as single layers with a minor proportion of few-layer arrangements, embedded in amorphous carbon. Xray diffraction, UV-visible diffuse reflectance, and thermogravimetry analysis were made in order to characterize the metal-organic salt precursor, showing that the perrhenate ions are dispersed widely from each other in the matrix of the organic cations, forming an inorganic-organic salt. The special arrangement of these ReS2 layers has a potential use as a heterogeneous catalyst due to the high proportion of edge sites. (C) 2016 Elsevier B.V. All rights reserved.

Silyl esters of perrhenic acid of the type R3SiOReO3 have been found to be thermally stable and readily accessible. Reaction of silver perrhenate with chlorotrimethylsilane in hexamethyldisiloxane as well as the reaction of rhenium heptoxide with hexamethyldisiloxane are reported to produce R3SiOReO3 in good yields.

The objective of this study was the utilization of three different biochars for pertechnetate removal from aqueous solutions. Biochars were prepared by slow pyrolysis from different feedstocks, characterized by BET, acid–base titration, SEM, XRD and FTIR and tested for their pertechnetate sorption using batch and dynamic techniques. Effect of various physico-chemical parameters such as contact time, pH and the presence of different ions in the solution on the sorption of pertechnetate onto biochars was investigated. Perrhenate as an analogue of pertechnetate was used for modeling of adsorption isotherms.

Four imidazolium perrhenates were synthesized, characterized and used as efficient catalysts for the oxidative esterification of benzaldehydes with alcohols. The perrhenates showed high catalytic activity toward oxidative esterifications, whereas good yields could be obtained for a series of aldehyde and alcohol substrates. The results indicate that the steric effects of functional groups on the aromatic ring play important roles in the formation of esters. Moreover, the alkyl structures of the alcohols also dramatically affect the product yields.

Materials based on the cationic copper(II) hexanuclear 18-membered metallacrown [18-MCCuII-N(2ph) -6] (2phH=2-piconyl hydrazide) and tetrafluoroborate, perchlorate, nitrate, sulfate, and perrhenate anions were prepared by an easy method in aqueous medium. Single-crystal X-ray characterization of six members of this new family of complexes showed that the anions are attached to the metallacrown by direct coordination to a copper cation or by hydrogen-bonding interaction with the center of the hexamer. The stable cationic nature of the complexes and their ability to bind different anions allows them to adsorb and immobilize environmentally relevant anions such as MO (M=Tc, Re). The MO trapping capacities suggest that these materials would be useful in the treatment of oxoanionic contaminants in water., Financial support from ERDF (EU), Ministerio de Ciencia e Innovación (Spain), and the Xunta de Galicia (Spain) under research projects CTQ2010-19386/BQU and 10TMT314002PR is gratefully acknowledged. A.B.L. thanks the Xunta de Galicia for a postdoctoral contract under the “Ángeles Alvariño” program.

The paper presents results of the study for obtaining perrhenic acid from aqueous ammonium perrhenate solutions by ion exchange. Two ways of perrhenic acid synthesis have been examined: sorption of perrhenate anion on selected anion exchange resins (followed by elution of the sorbed rhenium as HReO 4 ), and sorption of ammonium ion on selected cation exchange resins. The method of ammonium ion sorption on cation exchange resins has proved to be more effective. Using C 160 (H) cation exchange resin, perrhenic acid containing > 300 g/L of Re (after performing concentration in vacuum evaporator) has been obtained, with impurities concentration at the level of: 4 , ≤ 0.05 mg/L sodium, ≤ 0.20 mg/L potassium, ≤ 0.10 mg/L magnesium and ≤ 0.20 mg/L calcium.

Bimetal alkoxo complexes of rhenium, niobium, and tantalum with the general formula M4O2(OR)14(ReO4)2, where M = Nb or Ta and R = Me or Et, were prepared in ∼80% yield by reacting niobium or tantalum alkoxide M(OR)5 (R = Me or Et) with rhenium heptoxide Re2O7 in toluene. Comparative analysis of the molecular structures of the complexes was carried out by means of single-crystal X-ray diffraction and IR spectroscopy. The effect of the organic ligand and crystallization temperature on the geometry of the perrhenate group was studied. The solubility of the aforementioned alkoxo complexes in organic solvents increases with increasing hydrocarbon chain length of the ligand.

The separation of tungstate and perrhenate anions on alumina from aqueous solutions of sodium chloride was investigated in dynamic conditions. The breakthrough curves for W and Re as the function of the ratio of their concentrations in the solution, were determined. The flow rate (3 ml/min), pH 2 and NaCl concentration (0.15 mol/l) were kept constant throughout the experiments. The breakthrough capacities Q(0.05), the capacities at C/C-0 = 0.5, the total column sorption capacities Q(0.9) and the utilization degrees or column efficiencies E, were determined. According to the obtained data the separation factors alpha(W/Re) = Q(w)/Q(Re) were calculated.

This study is focused on the chelating process of two phosphonates with biological activity and therapeutic potential, HEDP (1-hydroxy-ethylidene-diphosphonic acid) and TTHMP (triethylene-tetramine-hexamethylene-phosphonic acid) with therapeutic radiometals 188Re (T1/2 = 17 hrs, Eβmax = 2.12 MeV, Eγ= 155 keV) and 177Lu (T1/2 = 6.7 days, Eβmax = 490 keV, Eγ = 208 keV). The ligand structure effect on the in vitro stability and on the biological affinity of the therapeutic agents was investigated. The radiochemical purity of the labeled compounds was higher than 95%, showing a good in vitro stability, up to 48 hours. The in vivo biodistribution studies, performed in rats, show a rapid and quantitative accumulation of both labeled compounds in bones and rapid elimination via the urinary tract. The maximum values of the bone uptake were ranged from 75.14% (injected dose/g organ) for 188Re-TTHMP to 94.10% for 177Lu-TTHMP. The structure of the chelates determines the kinetic of bone accumulation processes of labeled phosphonates. Its influence on the biodistribution of the radiolabeled phosphonates reveals that luthetium forms more stable chelate with polyphosphonate in respect to diphosphonate. On the other hand, the less reactive rhenium coupled with HEDP shows a better in vivo behavior than Re-TTHMP.

Aqueous reaction of Cu(BF4)2, NH4HF2, and pyrazine leads to formation of a novel 3D framework, [Cu(HF2)(pyz)2]BF4 (1), where 2D [Cu(pyz)2]2+ square layers are connected via HF 2 - . A second compound, Cu(ReO4)2(H2O)2(pyz) (2), was the result of our attempt to create the perrhenate analog of 1; a linear chain compound consisting of CuO4N2 octahedra linked through pyrazine ligands formed instead. Both compounds exhibit extensive hydrogen bonding interactions where bifluoride, F⋯H⋯F−, and O–H⋯O link layers and chains together in 1 and 2, respectively. Broad maxima indicative of short-range magnetic ordering (SRO) were observed in the magnetic susceptibility at 5.5 (1) and 7.7 K (2) while no evidence for the transition to long-range magnetic ordering (LRO) was detected above 2 K.

The crystal structure of the [Pt(NH3)5Cl](ReO4)3·2H2O salt is determined. Crystallographic data: a = 10.3476(2) A, b = 12.8955(2) A, c = 14.3536(3) A, β = 105.241(10)°, V = 1847.94(6) A3, space group P 21/n, Z = 4, d x = 3.962 g/cm3. Thermal decomposition of the compound is studied in a helium and hydrogen atmosphere. A two-phase product arises in the former case, in the latter a substitution Re0.75Pt0.25 solid solution with unit cell parameters: a = 2.767(2) A, c = 4.441(3) A, space group P63/mmc.

Compound cis,fac-[Mo(eta3-allyl)(CO)2(Hdmpz)3]BAr'4 (1) (Hdmpz = 3,5-dimethylpyrazole, Ar' = 3,5-bis(trifluoromethyl)phenyl) undergoes rapid substitution of one of the pyrazole ligands by anions, including the low nucleophilic ReO4-, a reaction that afforded [Mo(OReO3)(eta3-allyl)(CO)2(Hdmpz)2] (2), structurally characterized by X-ray diffraction. The new compounds fac-[Mn(CO)3(Hdmpz)3]BAr'4 (4a) and fac-[Mn(CO)3(HtBupz)3]BAr'4 (4b) (HtBupz = 3(5)-tert-butylpyrazole) also undergo pyrazole substitution with most anions, and the product from the reaction with nitrate was crystallographically characterized. Compounds 4a,b were found to be substitutionally stable toward perrhenate, and the adducts [Mn(CO)3(Hdmpz)3].[ReO4] (7a) and [Mn(CO)3(HtBupz)3].[ReO4].[Bu4N].[BAr'4] (7b), crystallographically characterized, display hydrogen bonds between one of the perrhenate oxygens and the N-H groups of two of the pyrazole ligands. The structurally similar adduct [Re(CO)3(Hdmpz)3].[ReO4] (8) was found to result from the interaction of [Re(CO)3(Hdmpz)3]BAr'4 with perrhenate. The reaction of [Re(OTf)(CO)5] with 3,5-dimethylpyrazole (Hdmpz) afforded [Re(CO)5(Hdmpz)]OTf (9). The reaction of 9 with Hdmpz and NaBAr'4 yielded [Re(CO)4(Hdmpz)2]BAr'4 (10), which was found to be unstable toward chloride anion. In contrast, the new compound fac,cis-[Re(CO)3(CNtBu)(Hdmpz)2]BAr'4 (11) is stable in solution in the presence of different anions. Binding constants for 11 with chloride, bromide, and nitrate are 1-2 orders of magnitude lower than those found for these anions and rhenium tris(pyrazole) hosts, indicating that the presence of the third pyrazole ligand is crucial. Compounds fac-[Re(CO)3(HPhpz)3]BAr'4 (14) (HPhpz = 3(5)-phenylpyrazole) and fac-[Re(CO)3(HIndz)3]BAr'4 (15) (HIndz = indazole) are, in terms of anion binding strength and selectivity, inferior to those with dimethylpyrazole or tert-butylpyrazole ligands.

Niobium and tantalum oxo-ethoxo-perrhenates, M 4 V O 2 ( OEt ) 14 ( ReO 4 ) 2 , are easily obtained in high yields via interaction of metal ethoxides, MV(OEt)5, with rhenium heptoxide, Re2O7, in hydrocarbon solvents. The complexes have good solubility in hexane and toluene and are stable in solution at room temperature. Their molecular structures are based on a tetranuclear M4(μ-O)2(μ-OR)4X12 core, X = OR, ReO4, composed of two pairs of edge-sharing octahedra joined via two almost linear oxo-bridges containing a rectangular flat M4-arrangement. The perrhenate ligands are attached in a centrosymmetric manner to the two opposite corners of the rectangle.

Equilibrium constants ( K MLA 0 / mo l − 1 d m 3 ) for the ion-pair formation of a complex ion NaL + with ReO 4 − in water were determined potentiometrically at 25 °C and the ionic strength ( I ) of 0 mol dm −3 using a Na + -selective electrode. Here, crown ethers, L, were 15-crown-5 ether (15C5), benzo-15C5, 18-crown-6 ether (18C6) and benzo-18C6. Also, NaReO 4 was extracted by the L into 1,2-dichloroethane and then extraction constants ( K ex /mol −2 dm 6 ) for the species, NaLReO 4 , were determined at 25 °C by AAS. These K ex values were resolved into four component equilibrium constants containing K MLA calculated at given I values. Based on these data, extraction-abilities of the L against the perrhenate were discussed in comparison with those of sodium picrate-L systems reported previously.

Coordination compounds of iron(II) perrhenate with 4-propyl-1,2,4-triazole (L), [Fe3L6(ReO4)4(H2O)2](ReO4)2(I), [Fe3L6(H2O)6](ReO4)6·H2O(II), and FeL3(ReO4)2(III), were synthesized. Compounds I and III were studied by static magnetic susceptibility measurements and by IR and electronic spectroscopy. These complexes exhibit a reversible 1 A 1 ⇄ 5 T 2 spin transition and thermochromism. Compound I exhibits a spin transition without hysteresis at 185 K. The temperatures of forward and reverse transition for III are 250 and 244 K, respectively. Complex II isolated by crystallization from an acidified aqueous solution of compound I has a linear trinuclear structure of the cation (X-ray diffraction data). The structure of complex I was assumed to be similar, while compound III has a polymeric structure.

The conditions of pertechnetate ion precipitation with ferroin nitrate in nitric acid solutions were determined. The effect of precipitation condition on the composition and structure of ferroin pertechnetate complexes was analyzed. At aging of the precipitate in the mother liquor the formation of nitrosyl group in the complex was found, which is confirmed by appearance in the IR spectrum of the band at 1700 cm−1 belonging to the coordinated nitrosyl group. Analysis of the IR spectra of ferroin perrhenate and pertechnetate complexes showed that coordinated nitrosyl group is formed only in the presence of technetium in the complex structure.

We report the synthesis of α,β-unsaturated acylsilanes via the perrhenate-catalyzed Meyer-Schuster rearrangement of 1-silylalkyn-3-ols. Propargylic alcohols derived from TES-acetylene and substituted benzaldehydes can be converted to acylsilanes using a combination of p-TSA·H(2)O and n-Bu(4)N·ReO(4), or Ph(3)SiOReO(3) in good yields. Some propargylic alcohols derived from ketones, as well as aliphatic and unsaturated aldehydes, can also be converted to acylsilanes; however, they were often prone to side reactions.

This study reports a method for preparation of pyrite nanoparticles and experimental results of reductive removal of perrhenate (a surrogate for radioactive pertechnetate) from water using the nanoparticles. The pyrite nanoparticles were prepared by ball milling in ethanol. Batch kinetic tests and column tests indicated that the pyrite nanoparticles were able to rapidly reduce and remove perrhenate at ambient temperatures. The pyrite nanoparticles were characterized using XRD and SEM. The effects of particle size and pH on the immobilization of perrhenate were studied in batch experiments with pyrite particles of different sizes (20 μm and 100 nm) and under different initial pH conditions (3.5, 6.6, and 12). To probe the potential of the nanoparticles for in situ immobilization of perrhenate in soil, column tests were carried out, where the pyrite nanoparticles were packed in the column to simulate a permeable reactive barrier. The column tests showed that the pyrite nanoparticles reduced the water leachable ReO4 − by 44 %. The results revealed great potential of pyrite nanoparticles for possible reductive immobilization of pertechnetate and other redox-sensitive metals and radionuclides in soil and groundwater.

A biomimetic heterogeneous catalyst combining palladium nanoparticles and an organic ligand-coordinated oxorhenium complex on activated carbon, Re(hoz)2-Pd/C, was previously developed and shown to reduce aqueous perchlorate (ClO4-) with H2 at a rate ∼100 times faster than the first generation ReOx-Pd/C catalyst prepared from perrhenate (ReO4-). However, the immobilized Re(hoz)2 complex was shown to partially decompose and leach into water as ReO4-, leading to an irreversible loss of catalytic activity. In this work, the stability of the immobilized Re(hoz)2 complex is shown to depend on kinetic competition between three processes: (1) ReV(hoz)2 oxidation by ClO4- and its reduction intermediates ClOx-, (2) ReVII(hoz)2 reduction by Pd-activated hydrogen, and (3) hydrolytic ReVII(hoz)2 decomposition. When ReV(hoz)2 oxidation is faster than ReVII(hoz)2 reduction, the ReVII(hoz)2 concentration builds up and leads to hydrolytic decomposition to ReO4- and free hoz ligand. Rapid ReV(hoz)2 oxidation is mainly promoted by highly reactive ClOx- formed from the reduction of ClO4-. To mitigate Re(hoz)2 decomposition and preserve catalytic activity, ruthenium (Ru) and rhodium (Rh) were evaluated as alternative H2 activators to Pd. Rh showed superior activity for reducing the ClO3- intermediate to Cl-, thereby preventing ClOx- buildup and lowering Re complex decomposition in the Re(hoz)2-Rh/C catalyst. In contrast, Ru showed the lowest ClO3- reduction activity and resulted in the most Re(hoz)2 decomposition among the Re(hoz)2-M/C catalysts. This work highlights the importance of using mechanistic insights from kinetic and spectroscopic tests to rationally design water treatment catalysts for enhanced performance and stability.

Technetium-99 (99Tc), a long-lived radionuclide, is one of the most widespread contaminants within the Hanford subsurface. At some depths, it is only extractable with strong acids, suggesting incorporation into a solid phase. We hypothesized that Tc may have coprecipitated with feldspathoid aluminosilicates under waste tanks that had leaked caustic solutions into the vadose zone. Our objectives were to determine if Tc could be incorporated into the feldspathoids cancrinite and sodalite and under what conditions coprecipitation could occur. Our hypothesis was that sodalite was more likely to incorporate and retain Tc. Our approach was to use known methods of feldspathoid formation in solutions resembling those in Hanford waste tanks contacting sediments in terms of major ion (Na, NO3, OH, Al(OH)4, and Si(OH)4 concentrations. In some cases, Al and Si were supplied from zeolite. We used perrhenate (ReO4) as a surrogate for pertechnetate (TcO4) to avoid the radioactivity. The major findings of this study were 1) ReO4 could be incorporated into either sodalite or cancrinite but the concentration in the solid was < 1% of the competing ion Cl, NO3, or NO2. 2) The small amount of ReO4 incorporated was not exchangeable with NO3 or NO2. 3) In sodalite, NO3 was highlymore » preferred over ReO4 but significant Re-sodalite was formed when the mole fraction in solution (Re/Re+N) exceeded 0.8. 4) A nonlinear relation between the unit cell parameter and amount of Re incorporated suggested that a separate Re-sodalite phase was formed rather than a solid solution. 5) We determined that sodalite preference for sodalite in the presence of different anions increased with the ionic size of the competing anion: Cl < CO3 < NO3 < SO4 < MnO4 < WO4 and significant incorporation did not occur unless the difference in anion radii was less than 12%. 6) Re(VII) was not significantly reduced to Re(IV) under the conditions of this experiment and Re appeared to be a good surrogate for Tc under oxidizing conditions as both oxyanions have the same size. In conclusion, incorporation of TcO4 is unlikely in the close proximity to the tanks where sodalite is likely to form in the presence of high NO3 and other anions much smaller than TcO4.« less

Quaternary ammonium perrhenates were applied as catalyst to promote the hydrolysis of cellulose in 1-allyl-3-methylimidazolium chloride ([Amim]Cl). The quaternary ammonium perrhenates displayed good catalytic performance for cellulose hydrolysis. Water was also proven to be effective to promote cellulose hydrolysis. Accordingly, 97% of total reduced sugar (TRS) and 42% of glucose yields could be obtained under the condition of using 5mol% of tetramethyl ammonium perrhenate as catalyst, 70μL of water, ca. 0.6mmol of microcrystalline cellulose (MCC) and 2.0g of [Amim]Cl as solvent under microwave irradiation for 30min at 150°C (optimal conditions). The influence of quaternary ammonium cation on the efficiency of cellulose hydrolysis was examined based on different cation structures of perrhenates. The mechanism on perrhenate catalyzed cellulose hydrolysis is also discussed, whereas hydrogen bonding between ReO4 anion and hydroxyl groups of cellulose is assumed to be the key step for depolymerization of cellulose.

The 1 : 4 and 1 : 2 complexes of silver perrhenate and triphenylphosphine, [(Ph3P)4Ag](+) ReO4(-) and [(Ph3P)2AgReO4]2, have been prepared and their structures determined in the solid state by X-ray diffraction. The former is composed of independent ions, while in the latter the ions are aggregated into cyclic dimers. The silver centers are tetracoordinated including contact with two bridging perrhenate anions, setting this structure apart from that of its gold analogue [(Ph3P)2Au](+) ReO4(-) where the gold centers are strictly two-coordinate.

In the discussion that follows some of the more recent progress in the area of anion binding by synthetic polyamine receptors is presented, with emphasis given to work undertaken by the authors’ groups. A continuing theme in these studies has been the relationship between receptor structure and its anion extraction properties. Systematic solvent extraction and structural studies for halide and perrhenate complexes with polyamines of tripodal, macrocyclic and macrobicyclic architecture that contain both aromatic moieties and four to eight amine functions have been performed in order to derive relevant structure-binding/extractability relationships. The results demonstrate that the binding and extraction behaviour of the polyamines towards halides and perrhenate is a complex function of their structural features, degree of protonation and lipophilic properties. The extraction is characterized by the preferred formation of mono- and diprotonated amine species in the organic phase. X-ray structure studies of iodide and perrhenate complexes with open-chain tetraamino derivatives and octaamino cryptands in different protonation states lead to the conclusion that in the first case only limited chelation of the anion occurs and in the second only highly protonated species are able to encapsulate the anion. The structural patterns observed are strongly influenced by the presence of water molecules in the crystals.

Copper(I) perrhenate, CuReO 4 , has been synthesized as a single-phase sample in sealed silica tubes at 500–800 °C, and its structure was determined for the first time by single-crystal X-ray diffraction. CuReO 4 forms a new structure type derived from the diamond-structure and crystallizes in space group I 4 1 cd with lattice parameters a =13.6965(5) A and c =7.7729(5) A, Z =16 (rotation method data acquisition using ω and ϕ scans, R 1 =0.0191, w R 2 =0.0403). Cu and Re atoms are tetrahedrally coordinated by O atoms, these tetrahedra are corner-shared, forming spirally twisted rings of 4-6-8-10- Me O 4 like Si x O y -rings in some silicon dioxide modifications or aluminosilicates. According to low-temperature powder X-ray diffraction and differential thermal analysis, CuReO 4 shows no phase transition down to 80 K and up to its melting point, 703 K.

A complex salt of tetraammineplatinum(II) perrhenate [Pt(NH3)4](ReO4)2 has been synthesized. Crystal data: a = 5.1847(6) A, b = 7.7397(8) A, c = 7.9540(9) A, α = 69.531(3)°, β = 79.656(3)°, γ = 77.649(3)°, V = 290,19(6) A3, space group \(P\bar 1\), Z = 1, dx = 4.370 g/cm3. The products of decomposition of [Pt(NH3)4](ReO4)2 in a hydrogen atmosphere were investigated using X-ray phase analysis. In definite temperature modes, these are Pt0.33Re0.67 solid solutions based on Re with hcp cell parameters a = 2.76 A, c = 4.42 A. The products of thermolysis obtained from other precursor complex salts containing both Pt and Re were investigated. Thus Pt0.75Re0.25 solid solution with a = 3.905(3) A was obtained from (NH4)2[ReCl6]0.25[PtCl6]0.75.

Complex salts, i.e., tetraamminepalladium perrhenate (I) and permanganate (II), are synthesized and studied by physicochemical methods. Their crystal structures are determined and thermal analysis is performed. The products formed in thermolysis of I and II carried out in the atmosphere of helium and hydrogen are studied. The Pd0.33Re0.67 solid solution based on Re is shown to form under particular temperature conditions in the atmosphere of hydrogen.

Na8(AlSiO4)6(ReO4)2 sodalite was synthesized using a hydrothermal method and its crystal structure was determined from Rietveld refinement of experimental X-ray powder diffraction data. The refinement showed that this compound adopts the cubic sodalite structure (space group P 4 ¯ 3 n , #218) with a = 9.1528 (1) A. Raman spectroscopic measurements confirm the presence of tetrahedral ReO 4 - groups. Broadening of the asymmetric stretching and bending vibrational modes suggests the tetrahedra are slightly distorted from ideal Td symmetry in the sodalite lattice. MAS NMR of 29Si and 27Al nuclei showed single intense peaks at δiso = −92.4 ppm and δiso = 57.5 ppm, respectively, confirming the alternating Si, Al tetrahedral ordering in sodalite deduced from the structural data. Chemical shifts for 29Si and 27Al calculated using correlative structural parameters (56.6 ± 0.8 ppm and −92.3 ± 0.9 ppm) showed good agreement with measured data indicating the validity of data derived from the Rietveld structural refinement.

The behavior of the receptors [Re(CO)3(Hdmpz)3]BAr'4 (Hdmpz = 3,5-dimethylpyrazole) (1) and [Re(CO)3(HtBupz)3]BAr'4 (HtBupz = 3(5)-tert-butylpyrazole) (2; Ar' = 3,5-bis(trifluoromethyl)phenyl) toward the anions fluoride, chloride, bromide, iodide, hydrogensulfate, dihydrogenphosphate, nitrate, and perrhenate was studied in CD3CN solution. In most cases, the receptors were stable. Anion exchange was fast, and binding constants were calculated from the NMR titration profiles. The structure of the adduct [Re(CO)3(HtBupz)3] x NO3 (3) was determined by X-ray diffraction. Two pyrazole moieties are hydrogen-bonded to one nitrate oxygen atom, and the third pyrazole moiety is hydrogen-bonded to an oxygen atom of an adjacent nitrate, leading to infinite chains. The structure of the adduct [Re(CO)3(Hdmpz)3]BAr'4acetone (4), also determined by X-ray diffraction, showed a similar interaction of two pyrazole N-H groups with the acetone oxygen atom. F- and H2PO4(-) deprotonate the receptors, and HSO4(-) decomposed 1. The structure of one of the decomposition products (5), determined by X-ray diffraction, is consistent with pyrazole protonation and substitution by sulfate.

Summary The radioactive concentrations of 99mTc/188Re from their generators are dependent upon the specific activity of 99Mo/188W, which dictates the bed size of the alumina/gel column and the volume of physiological saline needed as eluent. Because of the high content of inactive molybdenum/tungsten in neutron irradiated MoO3/WO3, large columns containing alumina/gel are needed to produce chromatographic 99Mo → 99mTc/188W → 188Re generators. This results in large elution volumes containing relatively high 99Mo/188W contents and low concentrations of 99mTc/188Re. The decrease in radioactive concentration, or specific volume, places a limitation on some of the clinical procedures. We report post elution concentration of 99mTc/188Re using in house prepared silver cation exchange and alumina column. The high bolus volumes (10 − 60 ml saline) can conveniently be concentrated in 1 ml of saline. This approach also works very effectively to yield high specific volume solutions of 99mTc-pertechnetate from a fission 99Mo loaded alumina generator towards the end of its normal working life.

Avoiding the use of toxic methyltin precursors to synthesize methyltrioxorhenium (MTO) and its mono- and bis-peroxo derivatives, applicable as oxidation catalysts, dimethyl zinc might be considered a promising alternative alkylating agent. However, the methylrhenium(VI) dimers, formed as reduction products alongside MTO during the reaction of dimethyl zinc with Re2O7, are not as straightforwardly transformed into the epoxidation catalysts as MTO itself in the presence of excess H2O2. In the case of red (μ-oxo)bis[trimethyloxorhenium(VI)], the main reaction product with H2O2 is the catalytically inactive trimethyldioxorhenium(VII). In the case of bis[dimethyl(μ-oxo)oxorhenium(VI)], slow conversion to the monomeric mono- and bis-peroxo congenes of MTO occurs. Furthermore, part of the Re(VI) starting complex is transformed into inactive perrhenate. While bis[dimethyl(μ-oxo)oxorhenium(VI)] might be applied (also in a mixture with MTO) as an oxidation catalyst precursor, (μ-oxo)bis[trimethyloxorhenium(VI)] can be applied as a useful precursor for the synthesis of trimethyldioxorhenium(VII), which was previously only accessible by less convenient synthetic pathways.

The radioisotopes (186)Re and (188)Re have been extensively investigated for various forms of radiotherapy due to their useful and high-abundance beta particle emissions, low-abundance and imageable gamma-rays, and chemical resemblance to technetium. In addition, (188)Re is available in no-carrier-added (NCA) form from long lived W-188 generators, whereas (186)Re can be produced in large quantities from reactors, although not in NCA form. However, NCA (186)Re can be produced on a cyclotron by a (p,n) reaction on (186)W. The purpose of this study was to compare labeling of the peptide bombesin with these three forms of rhenium radioisotopes. Cyclotron-produced NCA (186)Re was separated radiochemically from enriched (186)W (96.9%) targets using high-purity methyl ethyl ketone (MEK). The resulting (186)Re-MEK was then loaded onto a small alumina column to separate the resulting NCA (186)Re from any remaining (186)W. The experimental levels of impurities associated with (186)Re at the end of the separation process were found to be 5.7 x 10(-6) Ci of (182)Re (0.57%, t(1/2) = 12.7 h) and 1.283 x 10(-5) Ci of (182m)Re (1.28%, t(1/2) = 2.67 days). The radionuclidic purity of the separated (186)Re was found to be 99.6%, whereas the chemical identity was determined by reversed phase high-performance liquid chromatography (RP-HPLC) to be perrhenate ((186)ReO(4)(-)). Generator-produced (188)ReO(4)(-) from a (188)W/(188)Re generator (Oak Ridge National Laboratory) and CA (186)ReO(4)(-) produced from a (185)Re(n,gamma)(186)Re reaction at the University of Missouri Research Reactor (MURR) were used for comparison with the NCA (186)Re in subsequent studies. N(3)S-5-Ava-BBN(7-14)NH(2) conjugates provide flexibility for designing (186,188)Re-labeled conjugates that retain high in vitro and in vivo specificity targeting of GRP receptor-expressing cells. This study showed that the N(3)S-5-Ava-BBN(7-14)NH(2) could be labeled with (186,188)Re following the preconjugation, postmetallation approach. The (186,188)Re(V)O-N(3)S-5-Ava-BBN(7-14)NH(2) complexes were found to form stable complexes following the reduction of perrhenate (Re(VII)O(4)(-)) with stannous chloride at room temperature, as verified by HPLC and stability studies. The radiolabeling yield was found to be >90%. The HPLC chromatograms of (186,188)Re-N(3)S-5-Ava-BBN(7-14)NH(2) complexes revealed two peaks for each conjugate, reflecting the presence of syn- and anti-isomers, which were resolvable by HPLC but re-isomerized on separation. The biodistribution studies showed that the compounds were excreted through the renal and hepatobiliary systems and demonstrated receptor-specific uptake with an average pancreas accumulation of 8.15% ID/g at 1 h postinjection. Administration of cold BBN effectively blocked pancreatic uptake and further reflects the high specificity this conjugate has for the GRP receptors. At low levels of radioactivity, radiolysis effects were not observed. Scale-up may or may not elicit this effect, particularly for the higher energy beta emitter (188)Re. The biodistribution studies demonstrated that the CA and NCA (186,188)Re conjugates behaved similarly, raising the question of whether NCA (186,188)Re is necessary for specific tumor receptor targeting.