Shohel Mohammad, Bjorklund Jennifer L, Smith Jack A, Kravchuk Dmytro V, Mason Sara E, Forbes Tori Z
Department of Chemistry, University of Iowa, Iowa City, IA, 52242, USA.
Angew Chem Int Ed Engl. 2021 Apr 12;60(16):8755-8759. doi: 10.1002/anie.202017321. Epub 2021 Mar 9.
Keggin-type polyaluminum cations belong to a unique class of compounds with their large positive charge, hydroxo bridges, and divergent isomerization/oligomerization. Previous reports indicated that oligomerization of this species can only occur through one isomer (δ), but herein we report the isolation of largest Keggin-type cluster that occurs through self-condensation of four ϵ-isomers ϵ-GeAl to form [Ge O Al (OH) (H O) ] cluster (Ge Al ). The cluster was crystallized and structurally characterized by single-crystal X-ray diffraction (SCXRD) and the elemental composition was confirmed by ICP-MS and SEM-EDS. Additional dynamic light scattering experiments confirms the presence of the Ge Al in thermally aged solutions. DFT calculations reveal that a single atom Ge substitution in tetrahedral site of ϵ-isomer is the key for the formation of Ge Al because it activates deprotonation at key surface sites that control the self-condensation process.
Keggin型聚铝阳离子属于一类独特的化合物，具有大的正电荷、羟基桥以及不同的异构化/低聚作用。先前的报道表明，该物种的低聚只能通过一种异构体（δ）发生，但在此我们报告了通过四个ε-异构体ε-GeAl的自缩合形成[GeOAl(OH)(H₂O)]簇（Ge₉Al₉）而产生的最大Keggin型簇的分离。该簇通过单晶X射线衍射（SCXRD）进行结晶和结构表征，并通过电感耦合等离子体质谱（ICP-MS）和扫描电子显微镜-能谱仪（SEM-EDS）确认其元素组成。额外的动态光散射实验证实了热老化溶液中存在Ge₉Al₉。密度泛函理论（DFT）计算表明，ε-异构体四面体位置的单个Ge原子取代是形成Ge₉Al₉的关键，因为它激活了控制自缩合过程的关键表面位点的去质子化。
