Reactivity Differences of Rieke Zinc Arise Primarily from Salts in the Supernatant, Not in the Solids.
Reactivity Differences of Rieke Zinc Arise Primarily from Salts in the Supernatant, Not in the Solids.
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DOI：
10.1021/jacs.2c02471
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发表时间：
2022-07-13
影响因子：
15
通讯作者：
Blum, Suzanne A.
中科院分区：
文献类型：
--
作者：
Hanada, Erin M.;Tagawa, Tristen Kazumasa Soriano;Kawada, Masamu;Blum, Suzanne A.
与普遍的想法相反，发现上清液的盐含量决定了 Rieke 锌的不同制备方法对有机卤化物的氧化加成的反应性差异。这一结论是通过结合单颗粒显微镜和系综光谱实验，并在 Rieke 锌制备过程中小心去除或保留上清液而得出的。具有单 Rieke 锌颗粒分辨率的荧光显微镜实验确定了在没有上清液的情况下 Rieke 锌的微观表面反应性，从而确定了其固有的反应性，与复杂的上清液成分无关。在平行实验中，SEM、EDS、XPS 和 ICP-MS 在块体和单颗粒水平上表征了锌金属化学成分。 1 H NMR 光谱动力学表征了在存在和不存在不同上清液和外源盐添加剂的情况下的小规模 Rieke 锌反应性。总之，这些实验表明，钠还原的 Rieke 锌与锂还原的 Rieke 锌的反应性差异源于上清液中的残留盐，而不是固体的不同盐组成。该上清液盐还决定了最终有机锌产物的结构，生成二有机锌或单有机锌卤化物络合物。尽管 Rieke 锌被广泛使用，但之前并未报道过直接插入不同的 Rieke 锌制剂中形成不同的有机锌复合物。这些发现出人意料地表明，通过向用于制备金属的溶液中简单添加可溶性盐即可实现所需的 Rieke 锌反应性，这对有机锌试剂和纳米材料的合成产生了影响，这比固体成分和形态控制更容易进行合成操作。
Contrary to prevailing thought, the salt content of the supernatants is found to dictate reactivity differences of different preparation methods of Rieke zinc toward oxidative addition of organohalides. This conclusion is established through combined single-particle microscopy and ensemble spectroscopy experiments, coupled with careful removal or keeping of the supernatants during Rieke zinc preparations. Fluorescence microscopy experiments with single-Rieke-zinc-particle resolution determined the microscale surface reactivity of the Rieke zinc in the absence of supernatant, thus pinpointing its inherent reactivity independent of convoluting supernatant composition. In parallel experiments, SEM, EDS, XPS, and ICP-MS characterized zinc metal chemical composition at the bulk and single-particle levels. 1H NMR spectroscopy kinetics characterized bench-scale Rieke zinc reactivity in the presence and absence of different supernatants and exogenous salt additives. Together, these experiments show that the differences in reactivity from sodium-reduced vs. lithium-reduced Rieke zinc arise from the residual salts in the supernatant rather than the differing salt compositions of the solids. This supernatant salt also determines the structure of the ultimate organozinc product, generating either the diorganozinc or monoorganozinc halide complex. That different organozinc complexes formed upon direct insertion to different preparations of Rieke zinc was not previously reported, despite Rieke zinc’s widespread use. These findings impact organozinc-reagent and nanomaterial synthesis by showing that, unexpectedly, desired Rieke zinc reactivity can be achieved through simple addition of soluble salts to solutions that were used to prepare the metals—a substantially easier synthetic manipulation than solid composition and morphology control.
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