A Blueprint for the Stabilization of Sub-Valent Alkaline Earth Complexes**
A Blueprint for the Stabilization of Sub-Valent Alkaline Earth Complexes**
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亚价碱土配合物稳定的蓝图**
DOI：
10.1002/chem.202301850
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Bowles A
中科院分区：
文献类型：
--
作者：
Bowles A
低价第二族化学的研究是一个相对较新的研究领域，在2007年随着第一个Mg（I）二聚体的报告而建立。这些物种通过形成Mg-Mg共价键而稳定;然而，这种化学性质延伸到较重的碱土金属（AE）金属受到重大合成挑战的阻碍，主要与重AE-AE相互作用的不稳定性有关。在这里，我们提出了一个新的蓝图稳定的重AE（I）配合物，减少AE（II）前体与平面配位几何的基础上。我们报道了单齿酰胺{N（SiMe 3）2}-和{N（Mes）（SiMe 3）}-的均配三角平面AE（II）配合物的合成和结构表征。DFT计算表明，这些配合物的LUMO都表现出AE = Ca−Ba的特征.对正方形平面Sr（II）配合物[Sr{N（SiMe 3）2}（dioxane）2]∞的DFT分析显示了类似的前线轨道特征。AE（I）复合物，可以通过减少这些AE（II）的前体进行建模计算，揭示在所有情况下的放能形成。重要的是，NBO计算表明，在还原时，理论AE（I）产物的自组织轨道中保留了一些特征，这表明d轨道在获得稳定的重AE（I）络合物中起着至关重要的作用。
The study of sub‐valent Group 2 chemistry is a relatively new research field, being established in 2007 with the report of the first Mg(I) dimers. These species are stabilized by the formation of a Mg−Mg covalent bond; however, the extension of this chemistry to heavier alkaline earth (AE) metals has been frustrated by significant synthetic challenges, primarily associated with the instability of heavy AE−AE interactions. Here we present a new blueprint for the stabilization of heavy AE(I) complexes, based upon the reduction of AE(II) precursors with planar coordination geometries. We report the synthesis and structural characterisation of homoleptic trigonal planar AE(II) complexes of the monodentate amides {N(SiMe3)2}−and {N(Mes)(SiMe3)}−. DFT calculations showed that the LUMOs of these complexes all show somed‐character for AE = Ca−Ba. DFT analysis of the square planar Sr(II) complex [Sr{N(SiMe3)2}(dioxane)2]∞revealed analogous frontier orbitald‐character. AE(I) complexes that could be accessed by reduction of these AE(II) precursors were modelled computationally, revealing exergonic formation in all cases. Crucially, NBO calculations show that somed‐character is preserved in the SOMO of theoretical AE(I) products upon reduction, showing thatd‐orbitals could play a crucial role in achieving stable heavy AE(I) complexes.