Isolable Silicon-Based Polycations with Lewis Superacidity.
Isolable Silicon-Based Polycations with Lewis Superacidity.
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DOI：
10.1002/anie.202011696
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发表时间：
2020-12-14
期刊：
影响因子：
--
通讯作者：
Driess M
中科院分区：
文献类型：
--
作者：
Hermannsdorfer A;Driess M
分子硅多阳离子R2Si2+和RSi3+ （R=H，有机基团）是难以捉摸的路易斯超强酸，目前在缩合相中尚不清楚。在这里，我们报道了一系列可分离的三联吡啶稳定的R2Si2+和RSi3+配合物，[R2Si(terpy)]2+ (R=Ph 12 +; R2=C12H8 2 2+, (CH2) 32 2+)和[RSi(terpy)]3+ (R=Ph 4 3+，环己基5 3+，m -木基6 3+)，以它们的三酸盐形式合成。后者的稳定是通过更高的配位和降低氟离子亲和的代价来实现的，但理论和实验证实，刘易斯超酸性仍然保持在一个显著的水平。这些配合物激活了C(sp3)−F键，通过化学计量法从1氟adamantane （AdF）中提取氟化物并催化AdF的加氢脱氟。结晶加合物[2(F)]+和[5(H)]2+的形成特别证明了对氟化物和氢化物供体的高反应性。三吡啶配体与难以捉摸的气相分子R2Si2+和RSi3+的配位在保留Lewis超酸性特征的情况下提供了可分离的多阳离子配合物。广泛的标度和反应性研究揭示了迄今为止已知的硅基分子阳离子的最高刘易斯酸度。
Molecular silicon polycations of the types R2Si2+ and RSi3+ (R=H, organic groups) are elusive Lewis superacids and currently unknown in the condensed phase. Here, we report the synthesis of a series of isolable terpyridine‐stabilized R2Si2+ and RSi3+ complexes, [R2Si(terpy)]2+ (R=Ph 1 2+; R2=C12H8 2 2+, (CH2)3 3 2+) and [RSi(terpy)]3+ (R=Ph 4 3+, cyclohexyl 5 3+, m‐xylyl 6 3+), in form of their triflate salts. The stabilization of the latter is achieved through higher coordination and to the expense of reduced fluoride‐ion affinities, but a significant level of Lewis superacidity is nonetheless retained as verified by theory and experiment. The complexes activate C(sp3)−F bonds, as showcased by stoichiometric fluoride abstraction from 1‐fluoroadamantane (AdF) and the catalytic hydrodefluorination of AdF. The formation of the crystalline adducts [2(F)]+ and [5(H)]2+ documents in particular the high reactivity towards fluoride and hydride donors. Coordination of the terpyridine ligand to the elusive gas‐phase molecules R2Si2+ and RSi3+ affords isolable polycationic complexes under retention of Lewis superacidic features. Extensive scaling and reactivity studies reveal the highest Lewis acidity of a silicon‐based trication complex known to date for molecular Si‐based cations.
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