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The influence of fission product doping on the structure, composition, and electrochemical reactivity of uranium dioxide has been studied using X-ray diffractometry (XRD), scanning electron microscopy (SEM/EDX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Experiments were conducted on SIMFUEL specimens with simulated burn-ups (increasing doping levels) of 1.5, 3.0, and 6.0 atom%. As the dopant level increased, the lattice contracted, suggesting the dominant formation of dopant-oxygen vacancy clusters. The smaller than expected lattice contraction can be attributed to the segregation of Zr (one of eleven added dopants) to ABO3 perovskite-type phases that SEM/EDX shows also contain Ba, Ce, and possibly some U. Raman spectroscopy shows that doping leads to a loss of cubic symmetry, possibly associated with tetragonal distortions. Raman mapping confirms this loss of cubic symmetry and suggests the specimen is not uniformly doped. Electrochemical experiments show that these distortions lead to a decrease in the oxidative dissolution rate of the UO2 with increased doping density.Key words: UO2, X-ray diffraction, electrochemistry, Raman spectroscopy, nuclear fission products.

The effect of changing the bite angle of the dipyridyl ligand LL on the reactivity of the dimethylplatinum-(II) complexes [PtMe 2 (LL)] has been studied, by comparing complexes with the ligands LL ) di-2pyridylamine (DPA) or di-2-pyridyl ketone (DPK), which form a six-membered chelate ring, to compounds with 2,2′-bipyridyl derivatives, which form a five-membered chelate ring. The complex [PtMe 2 (DPA)] undergoes easy oxidative addition of methyl iodide to give the corresponding platinum(IV) complex [PtIMe 3 (DPA)]. Both [PtMe 2 (DPA)] and [PtMe 2 (DPK)] are protonated by acids HX at low temperature to give the hydridodimethylplatinum(IV) complexes [PtHXMe 2 (NN)] and [PtH(S)Me 2 (NN)]X (S ) solvent), which can exist in two isomeric forms with H trans to X or N. The structure of the complex [PtHClMe 2 (DPK)] was determined crystallographically. In a solution containing excess CD 3 OD, extensive hydrogen/deuterium exchange occurs into the methylplatinum groups and methane product at low temperature, indicating very easy reversibility of the exchange between hydridomethylplatinum(IV) and (methane)platinum(II) complexes. The hydridomethylplatinum(IV) complexes reductively eliminate methane at room temperature in solution but have significantly higher thermal stability and undergo more extensive H-D exchange than when NN ) 2,2′-bipyridyl. The reaction of [PtMe 2 (DPA)] with excess HCl gave [PtCl 2 (DPA)], and the reaction of [PtMe 2 (DPK)] with excess CF 3 SO 3 H gave the aqua complex [Pt(OH 2 ) 2 (DPK)](CF 3 SO 3 ) 2 or the binuclear hydroxo complex [Pt 2 (µ-OH) 2 (DPK) 2 ](CF 3 SO 3 ) 2 , depending on the experimental conditions.

The dimethylplatinum(II) complex [PtMe2(DPK)] (DPK = di-2-pyridyl ketone) undergoes easy oxidative addition to give platinum(IV) complexes. For example, reaction of [PtMe2(DPK)] with MeI gave [PtIMe3(DPK)], reaction with N-chlorosuccinimide in methanol gave [PtCl(OMe)Me2(DPK)], and reaction with [FN(CH2CH2)2NCH2Cl][BF4]2 in MeCN gave [PtF(NCMe)Me2(DPK)][BF4]. In several cases, the ketone group of the DPK ligand took part in the reactions. For example, oxidation of [PtMe2(DPK)] by air or hydrogen peroxide gave [Pt(OH)Me2(DPKOH)] (DPKOH = κ3-NN′O-(2-C5H4N)2C(OH)O), which reacted with HCl to give [PtClMe2(DPKOH)] or with excess acetyl chloride to give [PtCl2Me2(DPK)]. Reaction of [PtMe2(DPK)] with methyl triflate in MeCN solution gave [PtMe3(NCMe)(DPK)][OTf], which reacted with more MeOTf in the presence of base to give [PtMe3{DPC(OMe)2}][OTf], where DPC(OMe)2 = κ3-NN′O-(2-C5H4N)2C(OMe)2. Hydrolysis of [PtF(NCMe)Me2(DPK)][BF4] gave [Pt{NHC(=O)Me}Me2(DPKOH)], which crystallized in partially protonated form as an unusual supramolecular polymer [Pt{NHC(=O)Me}Me2(DPKOH)]·0.5HBF4.Key words: platinum, oxidative addition, ketone, pyridyl.

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