Perrhenate Groups Research Articles

Supramolecular assembly through intermolecular n → π* interactions through a coordinated perrhenate formed via superoxidation of Re(i) to Re(vii) in the formation of substituted Re(CO)3 complexes bearing Diimine ligands

Two Re(i) tricarbonyl complexes bearing Ph4TAP and dafone ligands and having a coordinated perrhenate group obtained via in situ superoxidation of Re(i) to Re(vii) have been characterized.

Comparative study of bimetal alkoxo complexes of rhenium, niobium, and tantalum by single-crystal x-ray diffraction and IR spectroscopy

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.

Structural Units in Three Uranyl Perrhenates

Three uranyl perrhenates have been synthesized, and their structures have been determined. (UO2)2(ReO4)4(H2O)3 (1) is triclinic, space group P, a=5.2771(7), b=13.100(2), c=15.476(2) A, alpha=107.180(2), beta=99.131(3), gamma=94.114(2) degrees, V=1001.12 A3, Z=2. [(UO2)4(ReO4)2O(OH)4(H2O)7](H2O)5 (2) is also triclinic, space group P, a=7.884(1), b=11.443(2), c=16.976(2) A, alpha=83.195(4), beta=89.387(4), gamma=85.289(4) degrees, V=1515.70 A3, Z=2. Na(UO2)(ReO4)3(H2O)2 (3) is monoclinic, space group C2/m, a=12.311(3), b=22.651(6), c=5.490(1) A, beta=109.366(6) degrees, V=1444.24 A3, Z=4. These compounds are the first structurally characterized uranyl perrhenates that do not contain organic ligands. In each structure, perrhenate groups coordinate uranyl ions at the equatorial vertices of pentagonal bipyramids. 1 contains complex chains of uranyl pentagonal bipyramids that are bridged by vertex sharing with perrhenate groups. The structural units in 2 and 3 consist of three novel finite clusters that include the coordination of uranyl ions with perrhenate. In general, weakly coordinating ligands such as perchlorate, perrhenate, and pertechnetate are assumed not to form stable complexes with uranyl in solutions or solids. The current findings, together with other recently reported studies, indicate each of these ligands can coordinate uranyl, and novel structure types result.

The Synthesis, Structural, and Spectroscopic Characterization of Uranium(IV) Perrhenate Complexes

We report the synthesis, structural, and spectroscopic characterization of a series of uranium(IV)-perrhenato complexes. Three isostructural complexes with general formula [U(ReO4)4(L)4] (where L = tri-n-butylphosphine oxide/TBPO (2), triethyl phosphate/TEP (3), or tri-iso-butyl phosphate/TiBP (4)), have been synthesized, both through the photoreduction of ethanolic {UO2}2+ solutions and also via a novel U(IV) starting material, U(ReO4)4.5H2O (1). Compound 1 has also been used in the preparation of [U(ReO4)4(TPPO)3(CH3CN)].2CH3CN (5) and [U(ReO4)(DPPMO2)3(OH)][ReO4]2.2CH3CN (6), where TPPO represents triphenylphosphine oxide and DPPMO2 represents bis(diphenylphosphino)methane dioxide. All six complexes have been spectroscopically characterized using NMR, UV-vis-NIR, and IR techniques, with 2, 3, 5, and 6 also fully structurally characterized. The U atoms in compounds 2-6 all exhibit eight-coordinate geometry with up to four perrhenate groups in addition to three (DPPMO2 and TPPO) or four (TEP, TiBP, TBPO) coordinated organic ligands. In the case of compounds 5 and 6, the coordination of eight ligands to the U(IV) center is completed by the binding of a solvent molecule (CH3CN) and OH-, respectively. Solid-state physical analysis (elemental and thermogravimetric) and infrared spectroscopy are in agreement with the structural studies. The crystallographic data suggest that the strength of the U(IV)-O-donor ligand bonds decreases across the series R3PO > [ReO4]- > (RO)3PO. Solution-state IR and 31P NMR spectroscopy appear to be in agreement with these solid-state results.

Alkoxide Route to Mixed Oxides of Rhenium, Niobium, and Tantalum. Preparation and X-ray Single-Crystal Study of a Novel Rhenium−Niobium Methoxo Complex, Nb2(OMe)8(ReO4)2

Thermal decomposition of complex oxomethoxo compounds Nb4O2(OMe)14(ReO4)2 (I) and Ta4O2(OMe)14(ReO4)2 (II) has been investigated. The decomposition of (II) at temperatures exceeding 100 °C results in the formation of MeOMe, MeOCH2OMe, MeOH, and H2O vapor and is accompanied by sublimation at temperatures over 135 °C. Plausible mechanisms of the processes studied are discussed. A new bimetallic methoxo compound, Nb2(OMe)8(ReO4)2 (III), was synthesized by interaction between Re2O7 and Nb2(OMe)10 in toluene solution and its structure was determined by means of an X-ray single-crystal study. The structure can be considered as a product of substitution for terminal methoxo groups with two perrhenate groups in dimeric Nb2(OMe)10 molecules. Decomposition of II in an inert atmosphere at 900 °C gave a Re−Ta mixed oxide phase, supposedly based on the L-Ta2O5 structure. Decomposition of I and III under similar conditions leads to the formation of rhenium−niobium oxide phases. The results obtained provide a basis for ...

Evaluation of three rhenium-188 candidates for intravascular radiation therapy with liquid-filled balloons to prevent restenosis

Background. Intravascular brachytherapy is an effective method for inhibiting coronary restenosis after percutaneous transluminal coronary angioplasty. A new concept for preventing restenosis is the use of a liquid-filled balloon containing a beta-ray-emitting radioisotope. Generator-produced rhenium-188 (Re-188) is a good candidate for intravascular brachytherapy. However, in the unlikely event of balloon rupture, release of Re-188 perrhenate may cause a high radiation dose to the thyroid and stomach. In this study, we compared the biodistributions of three Re-188 preparations (Re-188 perrhenate, Re-188 pentetic acid [DTPA], and Re-188 MAG3) to assess the radiation dose to organs in a rat model that mimicked balloon rupture. Methods and Results. After injection of Re-188 preparations intravenously, rats were killed at 10 minutes, 30 minutes, 60 minutes, 2 hours, and 6 hours (n = 5/group). Tissue concentrations were calculated and expressed as percent injected dose per gram or per milliliter. In addition, urine excretion and thyroid gland uptake were evaluated in rats (n = 5/group) with a gamma camera after administration of 37 MBq (1 mCi) of each agent. Our data showed all 3 agents were excreted primarily via urine. In the Re-188 MAG3 group, 82% was excreted within 1 hour, but in the Re-188 perrhenate group, only 28% was excreted. The biodistribution data for these agents revealed that radioactivity levels in the stomach and the thyroid gland were high in the perrhenate group but low in the Re-188 DTPA and Re-188 MAG3 groups. The concentration levels in other tissues including lung, liver, testis, muscle, and blood were low throughout this study for all 3 agents. The thyroid radiation values were 0.163, 0.0167, and 0.00728 mGy/MBq for Re-188 perrhenate, Re-188 DTPA, and Re-188 MAG3, respectively. The stomach radiation values were 0.127 mGy/MBq for Re-188 perrhenate, 0.013 mGy/MBq for Re-188 DTPA, and 0.0104 mGy/MBq for Re-188 MAG3. Conclusions. In the event of balloon rupture, the release of Re-188 MAG3 or Re-188 DTPA results in lower radiation doses than release of Re-188 perrhenate, especially to the thyroid gland and the stomach. (J Nucl Cardiol 2000;7:37–42.)

Rhenium-188-labeled DTPA: a new radiopharmaceutical for intravascular radiation therapy

Balloon angioplasty is a standard treatment for artherosclerotic coronary artery disease. However, its clinical value is reduced by a high restenosis rate. A new concept in preventing restenosis is the use of a liquid-filled balloon containing a beta-emitting radioisotope. In this study, we performed biodistribution studies of Re-188 perrhenate and Re-188 diethylenetriaminopentaacetate (DTPA) to assess the resulting organ dose values in the event of balloon rupture if these agents are used for the clinical inhibition of restenosis after percutaneous transluminal coronary angioplasty (PTCA). After injecting Re-188 preparations intravenously, rats were killed at 10 min, 30 min, 60 min, 2 h, and 6 h ( n =5 per group). Tissue concentrations were calculated and expressed as percent injected dose per gram or per milliliter (%ID/g or %ID/mL). In addition, urine excretion and thyroid gland uptake were evaluated in rats ( n =5 per group) with a gamma camera after administration of 37 MBq (1 mCi) of each agent. Our data showed that both agents were excreted primarily via urine. However, the excretion of Re-188 DTPA was much faster than that of Re-188 perrhenate via the urinary system. The biodistribution data revealed that radioactivity levels in the stomach and the thyroid gland were high in the perrhenate group but low in the Re-188 DTPA group. The concentration levels in other tissues including lung, liver, testis, muscle, and blood were low throughout this study for both agents. The thyroid radiation value in the Re-188 perrhenate group was 0.163 mGy/MBq, which was much higher than that of the Re-188 DTPA group (0.0167 mGy/MBq). The stomach radiation value was as high as 0.127 mGy/MBq for Re-188 perrhenate, compared with 0.013 mGy/MBq for Re-188 DTPA. In conclusion, in the event of balloon rupture, the release of Re-188 DTPA results in lower radiation doses than Re-188 perrhenate, especially to the thyroid gland and the stomach. Our data suggest that Re-188 DTPA is a useful radiopharmaceutical for endovascular irradiation.

Mehrfachbindungen zwischen Hauptgruppenelementen und Übergangsmetallen, LXXIX. / Multiple Bonds between Main Group Elements and Transition Metals, LXXIX.

Trimethylstannyl perrhenate, (CH3)3SnOReO3 (2), synthesized from dirheniumheptoxide and tetramethyltin, has a zigzag-chain crystal structure. This structure originates from catenation of individual molecules via the tin atom to a perrhenate group of another molecule. The tin atom thus forms the center of a trigonal-bipyramidal coordination geometry, with two oxygen atoms adopting apical positions while three methyl groups define the equatorial plane. The Re—O—Sn bonds alternate between linear and slightly bent. The zigzag-aggregation of the chain-structure results from the tetrahedral [ReO4] subunits. Ionic contributions to the Re—O—Sn bonds are not evident from the structural data, nor do data obtained from solution indicate any ionization such as [(CH3)3Sn]+[ReO4]⁻. Following the synthesis of the title compound 2, the heavier congener triphenylplumbyl perrhenate (5) has been synthesized from Re2O7 and Pb(C6H5)4.

Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen: XV. Reduktive aggregation des halbsandwich-komplexes trioxo(η 5-pentamethylcyclopentadienyl)rhenium

The trioxo complex (η 5-C 5Me 5)ReO 3 ( 1) undergoes partial deoxygenation in the presence of the Lewis base triphenylphosphane. When this reaction is conducted in tetrahydrofuran solution with rigorous exclusion of air, the dinuclear, very oxygen-sensitive d 2-Re V derivative 2 of composition (η 5-C 5Me 5) 2Re 2O 4 is cleanly formed. In the presence of trace amounts of oxygen, however, a second reaction pathway is opened up, which leads to the tetranuclear Re V/Re VII complex 3 in 30–60% yield. This compound is structurally derived from the dinuclear species 2, in that one of the two terminal oxo groups is replaced by two O-coordinated perrhenate ligands; in keeping with the requirements of the EAN rule and supported by the bond length of 265.1(1) pm, the doubly oxygen-bridged Re V-Re V interaction is best interpreted in terms of a metal—metal double bond (single-crystal X-ray diffraction study). Finally, upon treatment of 1 with triphenylphosphane in air-saturated solutions of tetrahydrofuran, the ionic cluster compound 4 of net composition (C 5Me 5) 3Re 5O 14 is surprisingly formed in 70–90% yield. This latter complex exhibits the C 3-symmetrical cation [(η 5-C 5Me 5) 3Re 3(μ-O) 6] 2+, with the two counter-ions being isolated perrhenate groups. The metal—metal distances within the cyclic cation are crystallographically identical and amount to 274.7(2) pm (single-crystal X-ray diffraction study).

Studies of rhenium–carboxylate complexes. III. The crystal and molecular structure of tetra-μ-n-butyratodirhenium(III) diperrhenate

One of the compounds obtained by the reaction of rhenium(III) chloride with n-butyric acid while exposed to oxygen has been shown by single crystal X-ray diffraction to be tetra-μ-n-butyratodi-rhenium(III) diperrhenate. The crystals are triclinic with lattice parameters a = 7.836(8) Å, b = 10.746(8) Å, c = 8.773(8) Å, α = 88.9(1)°, β = 106.5(1)°, and γ = 98.0(1)°. The space group is [Formula: see text] and there is one formula unit per cell. A total of 1593 independent reflections were examined and the structure was refined by full 3-dimensional least-squares to an R value of 0.123. Two rhenium environments are found, one consisting of a dimer unit bridged by 4 carboxylate groups and the other a per-rhenate group. This latter group, showing a mean Re—O distance of 1.75 Å, shares an oxygen atom with a rhenium atom in the dimer unit, and this Re—O bond length is 2.18 Å long. The structure results from packing of short chains, consisting of the dimer unit and the 2 perrhenate groups, running roughly parallel to the [111] direction.

Studies of rhenium–carboxylate complexes. I. Tris(μ-i-butyrato)di(chlororhenium(III)) perrhenate

One of the compounds obtained by reacting rhenium(III) chloride with isobutyric acid while exposed to oxygen has been shown by single crystal X-ray diffraction to be tris(μ-i-butyrato)di(chlororhenium(III)) perrhenate. The crystals are monoclinic with lattice parameters a = 8.980(5) Å, b = 17.790(8) Å, c = 15.361(8) Å, and β = 114.4(1)°. The space group is P21/c and there are 4 formula units per cell. A total of 1729 independent reflections were examined and the structure was refined by full three dimensional least squares to an R value of 0.114. Two Re environments are found, one consisting of a dimer unit bridged by three carboxylate groups with a chlorine atom per rhenium and the other as a perrhenate group. This latter group, showing a mean Re—O distance of 1.74 Å, shares an oxygen atom with a Re in the dimer unit, and this Re—O bond length is 2.28 Å long. The structure consists of a packing of chains of alternate dimers and perrhenate groups running parallel to the c axis.

Perrhenato complexes of bivalent cations

A series of complexes of the general formula [ML 4(ReO 4) 2] were prepared and studied: M = cobalt(II), copper(II), manganese(II), nickel(II) and zinc(II); L = pyridine(py) or 4-methylpyridine(4-mepy). Magnetic susceptibility measurements, infrared spectra (2.5 – 50μ), and near-infrared and visible spectra indicate coordination of the perrhenate groups to form tetragonally distorted octahedral complexes. Metal-ligand vibrations were assigned from the far-infrared spectral data, and Ds, Dt, Dq xy Dq z values of the nickel compounds were calculated from the near-infrared and visible spectral data. These studies indicate that the perrhenate anion coordinates more strongly than the perchlorate and tetra-fluoroborate anions and less strongly than the bromide and chloride anions.