Abstract The concept of hypercoordination has been extensively used and debated in the literature specifically in case of silicon complexes from the last three decades which has neither been proved nor disproved. In fact, all these silicon complexes reported in the literature consist of various bonding features i.e. covalent (C–Si, N–Si or X–Si), dative (N→Si or O→Si) and/or ionic (X-{Si+}, X = halogen). The present work compares the structural features of selected hypercoordinate silicon(IV) complexes derived from the hydrazide ligands and describes the relative stability aspects of penta- and hexa-coordinate hydrazide-based silicon dichelates with respect to the charge on central silicon atoms. Some selected examples of penta- and hexa-coordinate silicon complexes without having Si-halogen covalent bond reported in the literature were selected for the comparison of structural properties through DFT calculations. The results indicate that the electrophilicity on silicon atom in penta-coordinate silicon complexes are significantly higher, thus, indicating their better reactivity compared to their hexa-coordinate analogues.

中文翻译：

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酰肼基超配位硅 (IV) 配合物的稳定性和结构方面的研究

摘要 超配位的概念在文献中被广泛使用和争论，特别是在过去三十年的硅配合物的情况下，既未被证明也未被反驳。事实上，文献中报道的所有这些硅配合物都由各种键合特征组成，即共价键（C-Si、N-Si 或 X-Si）、配价（N→Si 或 O→Si）和/或离子键（X-{ Si+}，X = 卤素）。目前的工作比较了从酰肼配体衍生的选定超配位硅 (IV) 配合物的结构特征，并描述了五配位和六配位酰肼基硅二螯合物相对于中心硅原子电荷的相对稳定性方面。选择了文献中报道的一些没有硅卤素共价键的五配位和六配位硅配合物的选定例子，用于通过 DFT 计算比较结构特性。结果表明，五配位硅配合物中硅原子上的亲电性显着更高，因此表明与其六配位类似物相比，它们具有更好的反应性。