Sorbelli Diego, Rossi Elisa, Havenith Remco W A, Klein Johannes E M N, Belpassi Leonardo, Belanzoni Paola
Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto, 8, 06123 Perugia, Italy.
CNR Institute of Chemical Science and Technologies "Giulio Natta" (CNR-SCITEC), Via Elce di Sotto, 8, 06123 Perugia, Italy.
Inorg Chem. 2022 May 16;61(19):7327-7337. doi: 10.1021/acs.inorgchem.2c00174. Epub 2022 May 5.
The unconventional carbon dioxide insertion reaction of a gold-aluminyl [BuPAuAl(NON)] complex has been recently shown to be related to the electron-sharing character of the Au-Al bond that acts as a nucleophile and stabilizes the insertion product through a radical-like behavior. Since a gold-diarylboryl [IPrAuB(-tol)] complex with similar reactivity features has been recently reported, in this work we computationally investigate the reaction of carbon dioxide with [LAuX] (L = phosphine, N-heterocyclic carbene (NHC); X = Al(NON), B(-tol)) complexes to get insights into the Al/B anionic and gold ancillary ligand effects on the Au-Al/B bond nature, electronic structure, and reactivity of these compounds. We demonstrate that the Au-Al and Au-B bonds possess a similar electron-sharing nature, with diarylboryl complexes displaying a slightly more polarized bond as Au(δ)-B(δ). This feature reduces the radical-like reactivity toward CO, and the Al/B anionic ligand effect is found to favor aluminyls over boryls, despite the greater oxophilicity of B. Remarkably, the ancillary ligand of gold has a negligible electronic trans effect on the Au-X bond and only a minor impact on the formation of the insertion product, which is slightly more stable with carbene ligands. Surprisingly, we find that the modification of the steric hindrance at the carbene site may exert a sizable control over the reaction, with more sterically hindered ligands thermodynamically disfavoring the formation of the CO insertion product.
最近研究表明，金-铝基[BuPAuAl(NON)]配合物的非常规二氧化碳插入反应与Au-Al键的电子共享特性有关，该键作为亲核试剂，通过类似自由基的行为稳定插入产物。由于最近报道了具有类似反应活性特征的金-二芳基硼基[IPrAuB(-tol)]配合物，在这项工作中，我们通过计算研究了二氧化碳与[LAuX]（L = 膦、N-杂环卡宾（NHC）；X = Al(NON)、B(-tol)）配合物的反应，以深入了解Al/B阴离子和金辅助配体对这些化合物的Au-Al/B键性质、电子结构和反应活性的影响。我们证明，Au-Al键和Au-B键具有相似的电子共享性质，二芳基硼基配合物的键极化程度略高，呈Au(δ)-B(δ)形式。这一特征降低了对CO的类似自由基的反应活性，并且发现Al/B阴离子配体效应有利于铝基配合物而非硼基配合物，尽管B的亲氧性更强。值得注意的是，金的辅助配体对Au-X键的电子反位效应可忽略不计，对插入产物形成的影响也较小，卡宾配体使插入产物略更稳定。令人惊讶的是，我们发现卡宾位点空间位阻的改变可能对反应产生相当大的控制作用，空间位阻更大的配体在热力学上不利于CO插入产物的形成。
