观察者离子在水性金属阳离子化学中具有已知和新兴的作用,分别指导溶解度,物种形成,和反应性。这里,我们分离并在结构上表征了碱铀酰三过氧化物系列的最后两个亚稳态成员,Rb+和Cs+盐(Cs-U1和Rb-U1)。我们通过小角度X射线散射记录了它们的快速溶液聚合,与更稳定的Li+相比,Na+和K+类似物。为了了解碱的作用,我们还量化了碱金属氢氧化物促进的过氧化物去质子化和分解,其通常表现出随着碱尺寸的增加而增加的反应性。Cs-U1,最不稳定的铀酰三过氧化物单体,在固态环境中经历CO2的直接空气捕获,转换为Cs4[UVIO2(CO3)3],单晶X射线衍射证明,透射电子显微镜,和拉曼光谱。我们试图以Cs-U1向三碳酸铀酰的演变为基准,这涉及到一个短暂的,主要含有五价铀的不稳定吸湿性固体,通过X射线光电子能谱定量。粉末X射线衍射表明,这种中间状态包含CsUVO3的含水衍生物,其中母相已通过计算预测,但尚未合成。
Spectator ions have known and emerging roles in aqueous metal-cation chemistry, respectively directing solubility, speciation, and reactivity. Here, we isolate and structurally characterize the last two metastable members of the alkali uranyl triperoxide series, the Rb+ and Cs+ salts (Cs-U1 and Rb-U1). We document their rapid solution polymerization via small-angle X-ray scattering, which is compared to the more stable Li+, Na+ and K+ analogues. To understand the role of the alkalis, we also quantify alkali-hydroxide promoted peroxide deprotonation and decomposition, which generally exhibits increasing reactivity with increasing alkali size. Cs-U1, the most unstable of the uranyl triperoxide monomers, undergoes ambient direct air capture of CO2 in the solid-state, converting to Cs4[UVIO2(CO3)3], evidenced by single-crystal X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. We have attempted to benchmark the evolution of Cs-U1 to uranyl tricarbonate, which involves a transient, unstable hygroscopic solid that contains predominantly pentavalent uranium, quantified by X-ray photoelectron spectroscopy. Powder X-ray diffraction suggests this intermediate state contains a hydrous derivative of CsUVO3, where the parent phase has been computationally predicted, but not yet synthesized.