Preparation, characterization, and crystal, molecular, and electronic structure of (H2EDTA)99TcIV(.mu.-O)299TcIV(H2EDTA).cntdot.5H2O. A 2.33-.ANG. Tc-Tc distance which may represent a .sigma.2.pi.2.delta.*2 bond

Buergi, H. B.; Anderegg, G.; Blaêuenstein, P.

doi:10.1021/ic50225a046

Cited by 76 publications

(27 citation statements)

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“…Finally, Tc(IV) could be adsorbed as isolated complex on the surface of the iron oxide phase. Although interpretation of the results is complicated by tendency of Tc(IV) to form metal-metal bonds [17,18,22,23] and the fact that isomorphic substitution of Tc(IV) into an Fe(III) structure requires charge compensation, the final mechanism, surface sorption, best explains the EXAFS results.Bulk or surface precipitation of TcO 2 . xH 2 O was not observed at these pertechnetate concentrations and fraction surface coverage.…”

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confidence: 99%

Removal of Pertechnetate from Simulated Nuclear Waste Streams Using Supported Zerovalent Iron

et al. 2007

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The application of zero-valent iron nanoparticles or "Ferragels," either unsupported or supported, to the separation and reduction of pertechnetate anions (TcO 4 -) from complex waste mixtures was investigated as an alternative approach to current waste processing schemes. Although applicable to pertechnetate-containing waste streams in general, the tests reviewed here were directed at two specific potential applications at the U.S. Department of Energy's Hanford Site: (1) the direct removal of pertechnetate from highly alkaline solutions, typical of those found in Hanford tank waste; and (2) the removal of dilute pertechnetate from near neutral solutions, typical of the eluate streams from commercial organic ion-exchange resins that may be used to remediate Hanford tank wastes. It was envisioned that both applications would involve the subsequent encapsulation of the loaded sorbent material into a separate waste form. A high surface area (>200 m 2 /g) base-stable, nano-crystalline zirconia was used as a support for Ferragel for tests with highly alkaline solutions, while a silica gel support was used for tests with near neutral solutions. It was shown that after 24 hours of contact time, the high surface area zirconia supported Ferragel sorbent removed about 50% (K d = 370 L/kg) of the pertechnetate from a pH 14 tank waste simulant containing 0.51 mM TcO 4 -and large concentrations of Na + , OH -, NO 3 -, and CO 3 2-for a phase ratio of 360 L simulant per kg of sorbent. It was also shown that after 18 hours of contact time, the silica supported Ferragel removed >95% pertechnetate from a neutral pH eluate simulant containing 0.076 mM TcO 4 -for a phase ratio of 290 L/kg. It was determined that in all cases, Ferragels reduced the Tc(VII) to Tc(IV), or possibly Tc(V), through a redox reaction. Finally, it was demonstrated that a mixture of 20 mass % of the solid reaction products obtained from contacting zirconia support Ferragel with an alkaline waste solution containing Re(VII) -a surrogate for Tc(VII) -with 80 mass % alkali borosilicate based frit heat treated at 700°C for 4 hours sintered into a handleable waste form. INTRODUCTIONA vast amount of solid and liquid radioactive waste had been generated during the approximately thirty years since the world's first full-scale nuclear reactors and processing plants needed for the production and isolation of plutonium-239 began operating in 1944 at the Hanford Site River in southeastern Washington,. One reference [1] indicates that these wastes consist of approximately 208,000 m 3 of mixed waste in 177 underground storage tanks. Current emphasis at U.S. Department of Energy (DOE) and commercial sites has been directed at remediation of such radioactive wastes.One plan for Hanford Site tank wastes, for example, has been to separate the waste into primarily solid, i.e., sludge containing insoluble high-activity waste (HAW) species as well as non-radioactive solids, and aqueous liquid portions that will contain tank supernatant and watersoluble species derived from HAW...

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Removal of Pertechnetate from Simulated Nuclear Waste Streams Using Supported Zerovalent Iron

et al. 2007

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“…Since the rhenium ions in the diamagnetic complex 1 are formally in the + 4 oxidation state with a d 3 -d 3 electron configuration, it would indicate a Re`Re triple bond. A "longer than expected" Re`Re bond has been explained in terms of a σ 2 π 2 δ ⁎2 , rather than the conventional σ 2 π 2 δ 2 , electronic configuration [13]. The former configuration was supported by molecular orbital calculations, which intimated that the interaction of the orbitals of bridging ligands would place the energy of the δ orbital higher than that of the δ* orbital, thus providing some antibonding character to the Re`Re bond [8,13].…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 97%

“…A "longer than expected" Re`Re bond has been explained in terms of a σ 2 π 2 δ ⁎2 , rather than the conventional σ 2 π 2 δ 2 , electronic configuration [13]. The former configuration was supported by molecular orbital calculations, which intimated that the interaction of the orbitals of bridging ligands would place the energy of the δ orbital higher than that of the δ* orbital, thus providing some antibonding character to the Re`Re bond [8,13]. This may be due to the strong interaction of the p orbitals of the bridging oxo and bromide ions with the bonding molecular δ orbital.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 97%

A (μ-O)(μ-Br)ReIV2 metal–metal triple bond complex with a bridging tridentate ligand: Synthesis, structure and DFT study

Mukiza

Gerber

Hosten

et al. 2014

Inorganic Chemistry Communications

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“…Their ground states were assigned to be the B states, respectively, as assigned by the MRMP2 method. Two large absorption bands about 2.1 and 2.6 eV for A1 and A2 are theoretically assigned to be 1 1 Introduction S ulfur-bridged [1], halogen-bridged [2][3][4][5][6], and oxo-bridged [7][8][9][10][11] dinuclear complexes are very interesting because the metal centers take various oxidation states and various coordination numbers in these compounds. Especially, oxobridged rhenium, tungsten, and molybdenum complexes have attracted a lot of interests because their metal-metal distances are much shorter than those of other complexes, i.e., they should have strong metal-metal bond interaction [7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Theoretical investigation of μ‐O‐bridged dinuclear Re complexes: Electronic structure, bonding nature, and absorption spectra

Nakao

Saito

Sakaki

2009

Int J of Quantum Chemistry

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ABSTRACT:The ground state and some low-lying excited states of [Re B states, respectively, as assigned by the MRMP2 method. Two large absorption bands about 2.1 and 2.6 eV for A1 and A2 are theoretically assigned to be 1 1 B and 2 1 B states by the MRMP2 method. These energies are calculated to be 2.12 and 2.15 eV by the MRMP2 method, which are in good agreement with the experimental values of the similar complexes. Significant difference in absorption spectra of B from those of A1 and A2 are also discussed, based on MRMP2 calculations.

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Preparation, characterization, and crystal, molecular, and electronic structure of (H2EDTA)99TcIV(.mu.-O)299TcIV(H2EDTA).cntdot.5H2O. A 2.33-.ANG. Tc-Tc distance which may represent a .sigma.2.pi.2.delta.*2 bond

Cited by 76 publications

References 3 publications

Removal of Pertechnetate from Simulated Nuclear Waste Streams Using Supported Zerovalent Iron

Removal of Pertechnetate from Simulated Nuclear Waste Streams Using Supported Zerovalent Iron

A (μ-O)(μ-Br)ReIV2 metal–metal triple bond complex with a bridging tridentate ligand: Synthesis, structure and DFT study

Theoretical investigation of μ‐O‐bridged dinuclear Re complexes: Electronic structure, bonding nature, and absorption spectra

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