Xue Ying-Ying, Sui Jing-Jing, Xu Jing, Ding Yi-Hong
Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China.
Department of Chemistry, University of California, Irvine, California 92697-2025, United States.
ACS Omega. 2017 Sep 5;2(9):5407-5414. doi: 10.1021/acsomega.7b00487. eCollection 2017 Sep 30.
It is well-known that the chemistry of aluminum is dominated by Al(III) in the +3 oxidation state. Only during the past 2 decades has the chemistry of Al(I) and Al(II) been rapidly developed. However, if Al(I) and Al(III) are combined, the inherently high reactivities of Al(I) and Al(III) mostly result in their coupling with each other or interacting with surrounding elements, which easily results in significant deactivation or quenching of the desired oxidation states, as in the case of reported mixed valent Al-compounds. In this article, we report an unprecedented type of organoaluminum system, CAlR (R = H, SiH, Si(CH), SiPrDis, SiMe(SiBu)), whose lowest-energy structure, CAlR-, contains two Al(I) and two Al(III) atoms. The global nature and bonding motif of the parent CAlR- (R = H) were supported by an extensive global isomeric search, CBS-QB3 energy calculations, adaptive natural density partitioning, and bond order analysis. Interestingly and in sharp contrast to most organoaluminum species, CAlR- is associated with little multicenter bonding. CAlR- has a high feasibility of being observed either in the gas or condensed phases (with suitable substitutents). With well-separated Al(I) and Al(III), CAlR- (with suitable substitutents) could serve as the first Al/Al frustrated Lewis pair.
众所周知，铝的化学性质主要由处于 +3 氧化态的 Al(III) 主导。仅在过去 20 年里，Al(I) 和 Al(II) 的化学性质才得到迅速发展。然而，如果将 Al(I) 和 Al(III) 结合起来，Al(I) 和 Al(III) 固有的高反应活性大多会导致它们彼此偶联或与周围元素相互作用，这很容易导致所需氧化态的显著失活或猝灭，就像已报道的混合价态铝化合物那样。在本文中，我们报道了一种前所未有的有机铝体系，即 CAlR（R = H、SiH、Si(CH)、SiPrDis、SiMe(SiBu)），其能量最低的结构 CAlR⁻ 包含两个 Al(I) 原子和两个 Al(III) 原子。通过广泛的全局异构体搜索、CBS - QB3 能量计算、自适应自然密度划分和键级分析，证实了母体 CAlR⁻（R = H）的整体性质和键合模式。有趣的是，与大多数有机铝物种形成鲜明对比的是，CAlR⁻ 几乎没有多中心键合。CAlR⁻ 在气相或凝聚相（有合适的取代基）中都有很高的被观测到的可能性。由于 Al(I) 和 Al(III) 分隔良好，CAlR⁻（有合适的取代基）可以作为首个 Al/Al 受阻路易斯酸碱对。
