Synthesis and Structural Characterization of Alkaline-Earth-Metal Bis(amido)silane and Lithium Oxobis(aminolato)silane Complexes

Several of alkaline-earth-metal complexes [(η2:η2:μ(N):μ(N)-Li)+]2[{η2-Me2Si(DippN)2}2Mg]2– (4), [η2(N,N)-Me2Si(DippN)2Ca·3THF] (5), [η2(N,N)-Me2Si(DippN)2Sr·THF] (6), and [η2(N,N)-Me2Si(DippN)2Ba·4THF] (7) of a bulky bis(amido)silane ligand were readily prepared by the metathesis reaction of alkali-metal bis(amido)silane [Me2Si(DippNLi)2] (Dipp = 2,6-i-Pr2C6H3) and alkaline-earth-metal halides MX2 (M = Mg, X = Br; M = Ca, Sr, Ba, X = I). Alternatively, compounds 5–7 were synthesized either by transamination of M[N(SiMe3)2]2·2THF (M = Ca, Sr, Ba) and [Me2Si(DippNH)2] or by transmetalation of Sn[N(SiMe3)2]2, [Me2Si(DippNH)2], and metallic calcium, strontium, and barium in situ. The metathesis reaction of dilithium bis(amido)silane [Me2Si(DippNLi)2] and magnesium bromide in the presence of oxygen afforded, however, an unusual lithium oxo polyhedral complex {[(DippN(Me2Si)2)(μ-O)(Me2Si)]2(μ-Br)2[(μ3-Li)·THF]4(μ4-O)4(μ3-Li)2} (8) with a square-basket-shaped core Li6Br2O4 bearing a bis(aminolato)silane ligand. All complexes were characterized using 1H, 13C, and 7Li NMR and IR spectroscopy, in addition to X-ray crystallography.

数种位阻型双(酰胺基)硅烷配体的碱土金属配合物[(η2:η2:μ(N):μ(N)-Li)+]2[{η2-Me2Si(DippN)2}2Mg]2– (4)、[η2(N,N)-Me2Si(DippN)2Ca·3THF] (5)、[η2(N,N)-Me2Si(DippN)2Sr·THF] (6) 与[η2(N,N)-Me2Si(DippN)2Ba·4THF] (7)，可通过碱金属双(酰胺基)硅烷[Me2Si(DippNLi)2]（Dipp = 2,6-二异丙基苯基，2,6-i-Pr2C6H3）与碱土金属卤化物MX2（M=Mg，X=Br；M=Ca、Sr、Ba，X=I）的复分解反应便捷制备。此外，化合物5~7也可通过两条路径合成：其一为M[N(SiMe3)2]2·2THF（M=Ca、Sr、Ba）与[Me2Si(DippNH)2]的转胺反应；其二为Sn[N(SiMe3)2]2、[Me2Si(DippNH)2]与金属钙、锶、钡的原位转金属化反应。但当以氧气为助剂，通过[Me2Si(DippNLi)2]与溴化镁进行复分解反应时，却得到了一例特殊的含氧锂多面体配合物{[(DippN(Me2Si)2)(μ-O)(Me2Si)]2(μ-Br)2[(μ3-Li)·THF]4(μ4-O)4(μ3-Li)2} (8)，其核心为带有双(氨基酰胺基)硅烷配体、呈方篮状结构的Li6Br2O4簇。所有配合物均通过1H、13C及7Li核磁共振波谱（NMR，nuclear magnetic resonance spectroscopy）、红外光谱（IR，infrared spectroscopy）以及X射线晶体衍射（X-ray crystallography）完成表征。