Jess Kristof, Hanada Erin M, Peacock Hannah, Blum Suzanne A
Chemistry Department, University of California, Irvine, Irvine, CA 92697-2025.
Organometallics. 2020 Jul 27;39(14):2575-2579. doi: 10.1021/acs.organomet.0c00417. Epub 2020 Jul 14.
Yields of organoindium reagents synthesized from indium metal were previously reported to be highly dependent on metal batch and supplier due to the presence or absence of anticaking agent. Here, single-particle fluorescence microscopy established that MgO, an additive in some batches nominally for anticaking, significantly increased the physisorption of small-molecule organics onto the surface of the resulting MgO-coated indium metal particles. An inert and relatively nonpolar boron dipyrromethene fluorophore with a hydrocarbon tail provided a sensitive probe for this surface physisorption. SEM images revealed markedly different surface properties of indium particles either with or without MgO, consistent with their different physisorption properties observed by fluorescence microscopy. We further documented incomplete commercial bottle labeling regarding the presence and composition of this anticaking agent, both within our laboratory and previously in the literature, which may complicate reproducibility between laboratories. Trimethylsilyl chloride pretreatment, a step employed in a subset of reported synthetic procedures, removed the anticaking agent and produced particles with similar physisorption properties as commercial batches of indium powder distributed without the anticaking agent. These data indicate the possibility of an additional substrate/catalyst physisorption mechanism by which the anticaking agent may be influencing synthetic procedures that generate organoindium reagents from indium metal, in addition to simple anticaking.
由于是否存在抗结块剂，由铟金属合成的有机铟试剂的产率先前据报道高度依赖于金属批次和供应商。在此，单颗粒荧光显微镜确定，氧化镁（在某些批次中名义上作为抗结块剂的添加剂）显著增加了小分子有机物在所得氧化镁包覆的铟金属颗粒表面的物理吸附。一种带有烃链的惰性且相对非极性的硼二吡咯亚甲基荧光团为这种表面物理吸附提供了灵敏的探针。扫描电子显微镜图像显示了有或没有氧化镁的铟颗粒明显不同的表面性质，这与其通过荧光显微镜观察到的不同物理吸附性质一致。我们进一步记录了在我们实验室内部以及先前在文献中关于这种抗结块剂的存在和组成的商业瓶标签不完整的情况，这可能会使不同实验室之间的可重复性变得复杂。三甲基氯硅烷预处理（在所报道的一部分合成程序中采用的一个步骤）去除了抗结块剂，并产生了与未添加抗结块剂的市售铟粉批次具有相似物理吸附性质的颗粒。这些数据表明，除了简单的抗结块作用外，抗结块剂可能通过一种额外的底物/催化剂物理吸附机制影响从铟金属生成有机铟试剂的合成程序。
