Ghana Priyabrata, Rump Jens, Schnakenburg Gregor, Arz Marius I, Filippou Alexander C
Institute of Inorganic Chemistry, University of Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany.
J Am Chem Soc. 2021 Jan 13;143(1):420-432. doi: 10.1021/jacs.0c11628. Epub 2020 Dec 21.
While a variety of compounds containing planar tetracoordinated carbon (ptC), the so-called anti-van't Hoff/Le Bel carbon, are known experimentally, stable systems containing planar tetracoordinated silicon (ptSi) are barely known. As part of our studies on the application of stereoelectronically well-defined transition-metal fragments to stabilize silicon in unprecedented bonding modes, we report herein the synthesis and full characterization of a series of thermally stable complexes of the general formula [Tp'(CO)MSiC(R)C(R)M(CO)Tp'] (M = Mo, W; R = R = Me or R = H, R = SiMe, Ph; Tp' = κ-,',″-hydridotris(3,5-dimethylpyrazolyl)borate), which incorporate a ptSi atom in addition to two ptC atoms. The complexes were obtained by reacting the metallasilylidyne complexes [Tp'(CO)M≡Si-M(CO)(PMe)Tp'] with alkynes RC≡CR and were comprehensively analyzed by experimental studies and quantum chemical calculations. The analyses revealed that the ptSi atom is embedded in a tricyclic trapezoidal core featuring one internal SiC and two outer M-Si-C three-membered rings, which are fused via two Si-C bonds. The structural peculiarities evoked by the presence of an anti-van't Hoff/Le Bel ptSi center, such as the short M-Si bonds, a nearly linear M-Si-M spine, long M-C bonds, and the presence of two planar tetracoordinated carbon atoms were elucidated by a detailed analysis of the electronic structure, suggesting that one factor for the stabilization of the ptSi geometry is the aromaticity of the central SiC ring having two delocalized π electrons. Remarkably, the results further indicate the existence of both anti-van't Hoff/Le Bel carbon and silicon centers next to each other in the isolated complexes.
虽然实验上已知多种含有平面四配位碳（ptC），即所谓的反范特霍夫/勒贝尔碳的化合物，但含平面四配位硅（ptSi）的稳定体系却鲜为人知。作为我们关于应用立体电子定义明确的过渡金属片段以前所未有的键合模式稳定硅的研究的一部分，我们在此报告一系列通式为[Tp'(CO)MSiC(R)C(R)M(CO)Tp']（M = Mo、W；R = R = Me或R = H、R = SiMe₃、Ph；Tp' = κ-，'，″-氢三（3,5-二甲基吡唑基）硼酸盐）的热稳定配合物的合成及全面表征，这些配合物除了含有两个ptC原子外还包含一个ptSi原子。这些配合物是通过金属硅炔配合物[Tp'(CO)M≡Si-M(CO)(PMe₃)Tp']与炔烃RC≡CR反应得到的，并通过实验研究和量子化学计算进行了全面分析。分析表明，ptSi原子嵌入在一个三环梯形核中，该核具有一个内部SiC和两个外部M-Si-C三元环，它们通过两个Si-C键稠合。通过对电子结构的详细分析阐明了由反范特霍夫/勒贝尔ptSi中心的存在所引起的结构特性，如短的M-Si键、近乎线性的M-Si-M主链、长的M-C键以及两个平面四配位碳原子的存在，这表明稳定ptSi几何结构的一个因素是具有两个离域π电子的中心SiC环的芳香性。值得注意的是，结果进一步表明在分离的配合物中反范特霍夫/勒贝尔碳和硅中心彼此相邻存在。
