Pushing steric limits in osmium(IV) tetraaryl complexes
Pushing steric limits in osmium(IV) tetraaryl complexes
复制标题
突破锇(IV)四芳基配合物的空间限制
DOI：
10.1039/d2dt01706g
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发表时间：
2022
影响因子：
4
通讯作者：
Inkpen, Michael Stephen
中科院分区：
文献类型：
--
作者：
Parr, Joseph Michael;Olivar, Clarissa;Saal, Thomas;Haiges, Ralf;Inkpen, Michael Stephen
四芳基锇配合物的反应活性、性质和应用研究一直受到限制，因为它们的合成产率很低，通常由挥发性和有毒的OsO 4（通常≤34%）合成。在这里，我们表明，已知的空气稳定的M（芳基）4化合物（M = Os，Ru;芳基= 2-甲苯基，2，5-二甲苯基）可以以≤73%的产率使用新的、危险性较小的（Oct 4 N）2[MX6]前体（M = Os，Ru; X = Cl，Br）制备。这种方法也有利于制备Os（mesityl）4（Os3）的第一次，一个复杂的包含庞大的2，6-二甲基取代的芳基配体，虽然在低收率（5%）。为了更好地理解这些产率极值，我们通过合成另外两种具有不同2-取代的σ-芳基配体的新配合物来追踪Os（aryl）4的产率与配体空间体积之间的明确关系。这些化合物的单晶X-射线结构表明，所观察到的产率趋势反映了容易容纳芳基取代基到一个开放的口袋，直接位于每个M-芳基配位位点的对面。我们进行变温1H NMR研究Os3，利用“四面体”度量来评估Ru（aryl）4和Os（aryl）4材料中的几何畸变，并计算锥角和百分比掩埋体积度量以进一步说明和帮助量化σ-芳基配体的空间性质。Os（aryl）4的溶液循环伏安图表明，它们可逆的1-/0和0/1+氧化还原特性的电位可以通过改变芳基取代基来微调，并且Os3表现出以前在这类化合物中没有观察到的额外的1+/2+氧化还原事件。总之，这项工作有助于推进这些相对未被探索的有机金属配合物在分子材料科学的既定和新兴领域的潜在应用，例如扩展的分子框架和自组装单层，其中类似的四苯基甲烷和硅烷物种（M = C，Si）经常被作为目标。
Investigations into the reactivity, properties, and applications of osmium(IV) tetraaryl complexes have been hampered by their low yielding syntheses from volatile and toxic OsO4 (typically ≤34%). Here we show that known air-stable M(aryl)4 compounds (M = Os, Ru; aryl = 2-tolyl, 2,5-xylyl) can be prepared in ≤73% yields using new, less hazardous (Oct4N)2[MX6] precursors (M = Os, Ru; X = Cl, Br). This approach also facilitates the preparation of Os(mesityl)4 (Os3) for the first time, a complex comprising bulky 2,6-dimethyl substituted aryl ligands, albeit in low yield (5%). To better understand these yield extremes, we track, by synthesizing two additional new complexes with different 2-substituted σ-aryl ligands, a clear relationship between the yields of Os(aryl)4 and ligand steric bulk. Single-crystal X-ray structures of these compounds indicate that the observed yield trend reflects the ease of accommodating aryl substituents into an open pocket that lies directly opposite each M–aryl coordination site. We perform variable-temperature 1H NMR studies of Os3, utilize a “tetrahedricity” metric to assess geometric distortion in Ru(aryl)4 and Os(aryl)4 materials, and calculate cone angle and percentage buried volume metrics to further illustrate and help quantify σ-aryl ligand steric properties. Solution cyclic voltammograms of Os(aryl)4 show that the potentials of their reversible 1−/0 and 0/1+ redox features can be fine-tuned by varying aryl substituents, and that Os3 exhibits an additional 1+/2+ redox event not previously observed in this class of compounds. Taken together, this work helps to advance the potential application of these relatively underexplored organometallic complexes in established and emerging areas of molecular materials science, such as extended molecular frameworks and self-assembled monolayers, where analogous tetraphenylmethane and silane species (M = C, Si) have been frequently targeted.