29Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)-Silanide Bond Covalency.
29Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)-Silanide Bond Covalency.
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29Si NMR 光谱作为 s-和 f-区金属 (II)-硅烷化物键共价的探针。
DOI：
10.1021/jacs.1c03236
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发表时间：
2021
影响因子：
15
通讯作者：
Réant BLL
中科院分区：
文献类型：
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作者：
Réant BLL
我们报道了用29SiNMR谱和密度泛函计算相结合的方法，对S和f-嵌段金属-硅键的化学键的共价性进行了基准测试。合成并表征了配合物[M(SitBu3)2(THF)2(THF)x](1-M：M=Mg，Ca，Yb，x=0；M=Sm，Eu，x=1)和[M(SitBu2Me)2(THF)2(THF)x](2-M：M=Mg，x=0；M=Ca，Sm，Eu，Yb，x=1)。1-MAN2-M(M=Mg，Ca，Yb，No，由于实验不可用)以及已知的{Si(SiMe3)3}−-，{Si(SiMe2H)3}−-和{SiPh3}−-取代的类似物提供了20个具有代表性的例子，跨越五个硅酰胺配体和四个二价金属，揭示了当金属保持不变时，金属结合的29SiNMR各向同性化学位移δSi跨越一个很宽的(∼225 ppm)范围，并且在δSi和计算的原子离域指数和量子化学拓扑交换相关能之间发现了直接的线性相关关系，这些都是衡量键的共价性的指标。计算结果表明，这些硅酰胺络合物的成键以S轨道和d轨道为主，没有显著的f轨道贡献。相对地，当硅酰胺改变时，δSII由给定金属的顺磁屏蔽决定，而当金属改变给定配体时，则由自旋轨道屏蔽项决定。计算结果表明，它们的共价性顺序为：No(II)&Gt；Yb(II)&Gt；Ca(II)≈Mg(II)，这挑战了认为晚期榄系元素化学键等同于晚期稀土元素化学键的传统观点。
We report the use of29Si NMR spectroscopy and DFT calculations combined to benchmark the covalency in the chemical bonding of s- and f-block metal–silicon bonds. The complexes [M(SitBu3)2(THF)2(THF)x] (1-M: M = Mg, Ca, Yb,x= 0; M = Sm, Eu,x= 1) and [M(SitBu2Me)2(THF)2(THF)x] (2-M: M = Mg,x= 0; M = Ca, Sm, Eu, Yb,x= 1) have been synthesized and characterized. DFT calculations and29Si NMR spectroscopic analyses of1-Mand2-M(M = Mg, Ca, Yb, No, the lastin silicodue to experimental unavailability) together with known {Si(SiMe3)3}−-, {Si(SiMe2H)3}−-, and {SiPh3}−-substituted analogues provide 20 representative examples spanning five silanide ligands and four divalent metals, revealing that the metal-bound29Si NMR isotropic chemical shifts, δSi, span a wide (∼225 ppm) range when the metal is kept constant, and direct, linear correlations are found between δSiand computed delocalization indices and quantum chemical topology interatomic exchange-correlation energies that are measures of bond covalency. The calculations reveal dominant s- and d-orbital character in the bonding of these silanide complexes, with no significant f-orbital contributions. The δSiis determined, relatively, by paramagnetic shielding for a given metal when the silanide is varied but by the spin–orbit shielding term when the metal is varied for a given ligand. The calculations suggest a covalency ordering of No(II) > Yb(II) > Ca(II) ≈ Mg(II), challenging the traditional view of late actinide chemical bonding being equivalent to that of the late lanthanides.