Identification of the Limiting Species in the Plutonium(IV) Carbonate System. Solid State and Solution Molecular Structure of the [Pu(CO3)5]6- Ion

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• 作者：David L. Clark ; Steven D. Conradson ; D. Webster Keogh ; Phillip D. Palmer ; Brian L. Scott ; and C. Drew Tait
• 刊名：Inorganic Chemistry
• 出版年：1998
• 出版时间：June 15, 1998
• 年：1998
• 卷：37
• 期：12
• 页码：2893 - 2899
• 全文大小：145K
• 年卷期：v.37,no.12(June 15, 1998)
• ISSN：1520-510X

文摘

The identity of the limiting Pu(IV) species under highcarbonate concentrations has been determined to bePu(CO₃)₅^6-.Single crystals of[Na₆Pu(CO₃)₅]₂·Na₂CO₃·33H₂Owere obtained from a 0.15 M solution of Pu(IV)in 2.6M Na₂CO₃. The asymmetric unitcontains a complex network consisting of[Pu(CO₃)₅]^6-anions and Na⁺cations which are linked through interactions withCO₃^2- and H₂Oligands. Each Na⁺ ion is coordinated totheO atoms of H₂O orCO₃^2- ligands such that theNa⁺ ions achieve either octahedral or square-basedpyramidalcoordination. The[Pu(CO₃)₅]^6-anion can be viewed as a pseudohexagonal bipyramid with threeCO₃^2- ligandsin a equatorial plane and two in axial positions. EXAFS data forPu(IV) in 2.5M Na₂CO₃ solution werecollectedat the Pu L_III edge. Curve fitting reveals threeshells in the FT spectrum. The first shell contains ten Oatomswith Pu-O = 2.42(2) Å; the second shell was fit with five Catoms with Pu- - -C = 2.89(2) Å; and the thirdshellwas fit with five O atoms with Pu- - -O = 4.17(2) Å.These distances and coordination numbers correspondwellwith the average Pu-O, nonbonding Pu- - -C, and distal Pu- - -Odistances of 2.415(7), 2.874(9), and4.117(10)Å, respectively, found in the[Pu(CO₃)₅]^6-ion in the solid-state structure of[Na₆Pu(CO₃)₅]₂·Na₂CO₃·33H₂O.The UV-vis diffuse reflectance spectrum of a single crystal of[Na₆Pu(CO₃)₅]₂·Na₂CO₃·33H₂Oground into apowder is nearly identical to the solution absorption spectrum of thelimiting Pu(IV) carbonato complex in 2.5 MNa₂CO₃ solution. The peak by peakcorrespondence by position and relative absorption strengths, alongwithsolution EXAFS data, suggest that the Pu(IV) chromophore is thesame in both cases, and confirms that the[Pu(CO₃)₅]^6-ion is the limiting species in high carbonate solutions. Crystaldata for[Na₆Pu(CO₃)₅]₂·Na₂CO₃·33H₂O: monoclinic space groupP2₁/c (No. 14), a =9.860(2) Å, b = 17.427(2) Å, c =18.210(1) Å, mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> =101.42(1)mages/entities/deg.gif">, Z = 2, R₁ = 0.0337,wR₂ = 0.0775.