Monoanionic N,N-chelating triazenide ligands, [R-NNN-R]⁻, are compared to formamidinate or β-diketiminate ligands considerably less electron-donating and therefore potentially suitable for stabilizing electron rich metals in low oxidations states. A feature reported for silyl-substituted triazenide ligands, is their ability to eliminate N₂ resulting in (R₃Si)₂N⁻ anions. Here we describe a series of group 1 and 2 metal complexes with the very bulky bis-silyl-triazenide ligand [tBu₃Si-NNN-SitBu₃]⁻. Heteroleptic complexes could be isolated for Mg: {[(tBu₃Si)₂N₃]MgnBu}₂ or {[(tBu₃Si)₂N₃]MgI}₂, including its ether adducts. Despite bulky silyl substituents, the ligand did not stabilize heteroleptic [(tBu₃Si)₂N₃]AeN(SiMe₃)₂ complexes for Ca, Sr and Ba and only homoleptic Ae[(tBu₃Si)₂N₃]₂ complexes were isolated. Thermal decomposition of these complexes did result in N₂ elimination and formation of the expected amide complexes. Reduction of [(tBu₃Si)₂N₃]MgI ⋅ (Et₂O) with KC₈ in Et₂O led to the formation of a Mg^I complex with a Mg−Mg bond length of 2.902(1) Å. As only one of the Mg centres shows coordination with a Et₂O ligand, this is a rare example of an asymmetric Mg−Mg bond. This Mg^I complex is rather unstable in benzene solution, likely due to reduction of the ligand system. Triazenide ligands are therefore not suitable for stabilization of group 2 metals in low oxidation states.

中文翻译：

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碱土金属化学中的双甲硅烷基三氮烯化物配体

与甲脒或β-二酮亚胺配体相比，单阴离子N，N-螯合三氮烯化物配体[R-NNN-R] ^-的电子供给要少得多，因此可能适合在低氧化态下稳定富电子金属。据报道，甲硅烷基取代的三氮烯化物配体的一个特征是它们能够消除N ₂，从而产生(R ₃ Si) ₂ N ^-阴离子。在这里，我们描述了一系列具有非常大的双甲硅烷基三氮烯配体 [ t Bu ₃ Si-NNN-Si t Bu ₃ ] ^-的第 1 族和第 2 族金属配合物。可以分离出镁的杂配配合物：{[( t Bu ₃ Si) ₂ N ₃ ]Mg n Bu} ₂或{[( t Bu ₃ Si) ₂ N ₃ ]MgI} ₂，包括其醚加合物。尽管存在大量的甲硅烷基取代基，该配体并不能稳定Ca、Sr和Ba的杂配[( t Bu ₃ Si) ₂ N ₃ ]AeN(SiMe ₃ ) ₂配合物，并且只能稳定均配Ae[( t Bu ₃ Si) ₂ N ₃ ]分离出_2个复合物。这些络合物的热分解确实导致N ₂消除并形成预期的酰胺络合物。在Et 2 O 中用 KC ₈还原 [( t Bu ₃ Si) ₂ N ₃ ]MgI ⋅ (Et ₂ O)导致形成 Mg ^I络合物，其 Mg−Mg 键长为 2.902(1) Å _。由于只有一个 Mg 中心显示出与 Et ₂ O 配体的配位，因此这是不对称 Mg−Mg 键的罕见例子。该 Mg ^I络合物在苯溶液中相当不稳定，可能是由于配体系统的还原。因此，三氮烯​​化物配体不适合稳定低氧化态的第2族金属。