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Mebi C.A.,Arkansas Tech University | Karr D.S.,Arkansas Tech University | Noll B.C.,Bruker AXS Inc.
Polyhedron | Year: 2013

Diiron-carbonyl complexes coupled to naphthalene-2-thiolate ligands, [(μ-naphthalene-2-thiolato)2Fe2(CO)6] (1) and [(μ-naphthalene-2-thiolato)2Fe2(CO) 5PPh3] (2), have been usefully prepared and structurally characterized. As models for the active site of hydrogenase enzymes, these compounds have been examined as electrocatalysts for the reduction of proton to produce molecular hydrogen. In the presence of acetic acid, 1 and 2 catalyze the electrochemical production of molecular hydrogen with mild overpotentials of -0.54 and -0.51 V versus Fc/Fc+, respectively. The overpotential for compound 1 is 260 mV smaller than that of the analogous compound, [(μ-SPh)2Fe2(CO)6]. © 2012 Elsevier Ltd. All rights reserved. Source


West J.K.,University of North Dakota | Fondong G.L.,University of North Dakota | Noll B.C.,Bruker AXS Inc. | Stahl L.,University of North Dakota
Dalton Transactions | Year: 2013

Because of the increasing importance of N-heterocyclic carbenes in organometallic chemistry we investigated the ligand properties of structurally-related acyclic and cyclic heavier carbene analogues with transition metal chlorides. Acyclic {(Me3Si)2N} 2El, El = Ge and Sn, react with CuCl with transfer of one (Me 3Si)2N ligand to yield the known copper tetramer {(Me 3Si)2NCu}4. The cyclic Me2Si(μ- NtBu)2Ge, by contrast, binds copper through germanium only, furnishing a tetranuclear ladder structure with both terminal and bridging germylenes. The tin homologue, however, inserts into the CuCl bond, and the ensuing {Me2Si(μ-NtBu)2SnCl}- ions then coordinate one copper ion via their tin atoms while sandwiching the remaining three copper ions in an unprecedented κ2-N,N′ fashion. Chemically-harder Cr(ii) - created in a redox reaction of Me 2Si(μ-NtBu)2Sn with CrCl3(THF) 3 - is not coordinated by tin, but chelated by both nitrogen atoms of one {Me2Si(μ-NtBu)2SnCl}- ion and more weakly through the tin-bound chloride. This journal is © 2013 The Royal Society of Chemistry. Source


Nyman M.,Sandia National Laboratories | Rodriguez M.A.,Sandia National Laboratories | Campana C.F.,Bruker AXS Inc.
Inorganic Chemistry | Year: 2010

The hexavalent uranium specie, uranyl triperoxide, UO2(O 2)3 4-, has been shown recently to behave like high oxidation-state d0 transition-metals, self-assembling into polyoxometalate-like clusters that contain up to 60 uranyl cations bridged by peroxide ligands. There has been much less focus on synthesis and structural characterization of salts of the monomeric UO2(O2) 3 4- building block of these clusters. However, these could serve as water-soluble uranyl precursors for both clusters and materials, and also be used as simple models to study aqueous behavior by experiment and modeling. The countercation is of utmost importance to the assembly of these clusters, and Li+ has proven useful for the crystallization of many of the known cluster geometries to date. We present in this paper synthesis and structural characterization of two monomeric lithium uranyl-peroxide salts, Li4[UO2(O2)3] 10H2O (1) and [UO2(O2)3]12[(UO 2(OH)4)Li16(H2O)28] 3 Li6[H2O]26 (2). They were obtained from aqueous-alcohol solutions rather than the analogous aqueous solutions from which lithium uranyl-peroxide clusters are crystallized. Rapid introduction of the alcohol gives the structure of (1) whereas slow diffusion of alcohol results in crystallization of (2). (2) is an unusual structure featuring uranyl-centered alkali clusters that are linked into ring and spherical arrangements via [UO2(O2)3] anions. Furthermore, partial substitution of Rb or Cs into the synthesis results in formation of (2) with substitution of these larger alkalis into the uranyl-centered clusters. We surmise that the slow crystallization allows for direct bonding of alkali metals to the uranyl-peroxide oxygen ligands that is observed in (2), and its Rb and Cs-substituted derivatives. In contrast, the only interaction between UO2(O2)3 4- and Li+ observed in (1) is through hydrogen bonding of the lithium-bound water. These structures potentially provide some insight to understanding how alkali counterions interact with the UO2(O 2)3 4- anions during the self-assembly, crystallization and even redissolution of uranyl-peroxide polyanionic clusters. © 2010 American Chemical Society. Source


Ying J.-W.,Purdue University | Liu I.P.-C.,Purdue University | Xi B.,Purdue University | Song Y.,Nanjing University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2010

(Figure Presented) Ru communicating? Butadiyn-diyl bridges link three Ru2 moieties together to give a molecular wire (see structure, red Ru, green C, blue N, purple O). Voltammetric, spectroscopic, and magnetic data all point to extensive electronic derealization across the linear trimer. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Source


Shaw B.J.,Amgen Inc. | Semin D.J.,Amgen Inc. | Rider M.E.,Bruker AXS Inc. | Beebe M.R.,Technos International Inc.
Journal of Pharmaceutical and Biomedical Analysis | Year: 2012

Palladium (Pd) is extensively used in pharmaceutical small molecule drug substance processes, however it must be removed prior to release of the active pharmaceutical ingredient (API). Evaluation of four TXRF instruments and configurations were compared to ICP-MS instrumentation for trace metal analysis, most importantly for Pd. Standards and six pharmaceutical drug substances, triprolidine HCl, diphenhydramine HCl, chlorpheniramine maleate, pseudoephedrine HCl, ephedrine sulfate, and scopolamine HBr, were analyzed to determine linearity, sensitivity, accuracy, and precision for Pd plus Cr, Fe, Cu, Rh, and Pt versus interferences, particularly from Cl, S, and Ar, on the various X-ray fluorescence lines. Irrespective of instrument platform, in general X-ray sources capable of accessing Pd-K lines were found to be most effective in determination of Pd in APIs. © 2012 Elsevier B.V.. Source

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