Shan Changkai, Dong Shicheng, Yao Shenglai, Zhu Jun, Driess Matthias
Metalorganics and Inorganic Materials, Department of Chemistry, Technische Universität Berlin, Straße des 17, Juni 135, Sekr. C2, 10623 Berlin, Germany.
State Key Laboratory of Physical Chemistry of Solid Surfaces and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, 361005 Xiamen, China.
J Am Chem Soc. 2023 Apr 5;145(13):7084-7089. doi: 10.1021/jacs.3c00722. Epub 2023 Mar 21.
For a long time, planar tetracoordinate carbon (ptC) represented an exotic coordination mode in organic and organometallic chemistry, but it is now a useful synthetic building block. In contrast, realization of planar tetracoordinate silicon (ptSi), a heavier analogue of ptC, is still challenging. Herein we report the successful synthesis and unusual reactivity of the first ptSi species of divalent silicon present in , supported by the chelating bis(-heterocyclic silylene)bipyridine ligand, 2,2'-{[(4-BuPh)C(NBu)]SiNMe}(CN), ]. The compound resulted from direct reaction of with Idipp-SiI [Idipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]. Alternatively, it can also be synthesized by a two-electron reduction of the corresponding Si(IV) precursor with 2 molar equiv of KCH. Density functional theory calculations show that the lone pair at the ptSi(II) resides almost completely in its 3 orbital, very different from known four-coordinate silylenes. Oxidative addition of MeI to the ptSi(II) atom affords the corresponding pentacoordinate Si(IV) compound , with the methyl group located in an apical position. Remarkably, the reaction of with [CuOBu] leads to the regeneration of the bis(silylene) arms via Si-Si bond scission and induces the Si(II) → Si(IV) oxidation of the central Si(II) atom and concomitant two-electron reduction of the bipyridine moiety to form the neutral bis(silylene)silyl Cu(I) complex .
长期以来，平面四配位碳（ptC）在有机化学和有机金属化学中代表着一种奇特的配位模式，但如今它已成为一种有用的合成砌块。相比之下，平面四配位硅（ptSi）作为ptC的较重类似物，其实现仍然具有挑战性。在此，我们报道了由螯合双（-杂环硅烯）联吡啶配体2,2'-{[(4-BuPh)C(NBu)]SiNMe}(CN) ]支撑的首个二价硅的ptSi物种的成功合成及其异常反应性。该化合物由 与Idipp-SiI [Idipp = 1,3-双（2,6-二异丙基苯基）咪唑-2-亚基]直接反应制得。或者，它也可以通过用2摩尔当量的KCH对相应的Si(IV)前体 进行双电子还原合成。密度泛函理论计算表明，ptSi(II)上的孤对电子几乎完全位于其3轨道，这与已知的四配位硅烯非常不同。MeI对ptSi(II)原子的氧化加成得到相应的五配位Si(IV)化合物，并使甲基位于顶端位置。值得注意的是， 与[CuOBu]的反应通过Si-Si键断裂导致双（硅烯）臂再生，并诱导中心Si(II)原子发生Si(II)→Si(IV)氧化以及联吡啶部分伴随双电子还原，从而形成中性双（硅烯）硅基Cu(I)配合物 。
