- The 2-Arsaethynolate Anion: Synthesis and Reactivity Towards Heteroallenes
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The synthesis and isolation of the 2-arsaethynolate anion, AsCO?, and its subsequent reactivity towards heteroallenes is reported. Reactions with ketenes and carbodiimides afford four-membered anionic heterocycles in formal [2+2] cycloaddition reactions. By contrast, reaction with an isocyanate yielded a 1,4,2-diazaarsolidine-3,5-dionide anion and the unprecedented cluster anions As102?and As124?. These preliminary reactivity studies hint at the enormous potential synthetic utility of this novel anion, which may be employed as an arsenide (As?) source.
- Hinz, Alexander,Goicoechea, Jose M.
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- Flux requirements for the growth of RFeAsO (R=rare earth) superconductors
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Millimeter-sized LaFeAsO single crystals have been successfully grown out of NaAs flux starting with (LaAs+1/2 Fe2 O3):20NaAs. The factors which allow the growth of these crystals out of NaAs but not out of many other fluxes, such as FeAs, have been investigated. X-ray powder diffraction found that NaAs synthesized for the growth of RFeAsO superconductors has monoclinic LiAs structure. Thermal analysis confirmed that NaAs melts congruently at about 600 °C. The ability to extract RFeAsO crystals from this NaAs flux suggests that NaAs has a significant oxygen solubility, possibly due to the formation of the ternary compound NaAsO2, and enough oxygen diffusivity to transport solute to the growth front. Oxygen solubility and diffusivity are two important factors in searching for an alternative environmentally benign flux for the growth of RFeAsO superconductors.
- Yan,Jensen,Dennis,McCallum,Lograsso
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- Electrochemical Oxidation of the Phospha- and Arsaethynolate Anions, PCO– and AsCO–
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The anions PCO– and AsCO– are shown to be electroactive and are studied in aqueous and non-aqueous solutions. Cyclic voltammetry is used to extract fundamental physicochemical parameters such as oxidation peak potentials, and transfer and diffusion coefficients of the anions to better understand the nature of the oxidation process. Variation of the potential scan rate reveals that electro-oxidation of PCO– with the release of CO is controlled by diffusion and is a one-electron irreversible process yielding phosphorus-containing deposits. In contrast, the oxidation of AsCO– is a near electrochemically reversible process, forming pure arsenic deposits, with a chemically irreversible follow-up reaction. For both anions, the electrode surface is substantially “blocked” by the reaction products. The formed deposits were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy.
- Tambornino, Frank,Tanner, Eden E. L.,Amin, Hatem M. A.,Holter, Jennifer,Claridge, Tim,Compton, Richard G.,Goicoechea, Jose M.
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