Silicon-Halogen Bond Activation in Mixed Si/Al Compounds and an Approach to Intramolecular Stabilized Silylium Ions
Silicon-Halogen Bond Activation in Mixed Si/Al Compounds and an Approach to Intramolecular Stabilized Silylium Ions
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DOI：
10.1002/ejic.201801273
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发表时间：
2019-02
影响因子：
2.3
通讯作者：
W. Uhl;Michael Tolzmann;Kira Willeke;Christian Honacker;A. Hepp;M. Layh;E. Würthwein
中科院分区：
文献类型：
--
作者：
W. Uhl;Michael Tolzmann;Kira Willeke;Christian Honacker;A. Hepp;M. Layh;E. Würthwein
通过配位不饱和Al原子官能化的烯基氯硅烷，R“”（R“）Si（Cl）C（AltBu 2）=C（H）R5[R =tBu，cHex，1-Ad，Ph，3，5-（F3 C）2C 6 H3; R”= Mes，Ph，4-tBuC 6 H4，4-tBuOC 6 H4，4-Et 2NC 6 H4，tBu; R“"= Mes，CH（SiMe 3）2，tBu]，以良好的产率通过相应的炔基氯硅烷R”“（R”）Si（Cl）C（AltBu 2）= C（H）R5与tBu 2Al-H的氢铝化获得。它们通过分子内Al-Cl相互作用以四元、接近平面SiCAlCl杂环为特征。Si-Cl键的活化导致键从3中的约209 μ m延长到化合物5中的220至225 μ m。29 Si的NMR共振峰向低场移动，从5a [R =tBu，R′ = R′′ = Mes]的δ= 24.0到5 j [R = R′ = R ′ ′ =tBu]的δ= 68.1。后一个值接近溶剂配位的甲硅烷基阳离子如Et 3Si（C6 H5 Me）+的值。相关的氟化物R′（tBuC <$C）Si（F）C（AltBu 2）C = C（H）tBu 9（R′ = Ph，Mes）类似地通过炔基硅烷R′Si（F）（C <$C-tBu）28的氢铝化获得。化合物9通过Si-F-Al桥形成二聚体并形成八元C2 Al 2Si 2F 2杂环。δ= -4.7和-14.7的29 Si NMR位移以及约170 pm的Si-F键长表明存在四配位共价键合的Si原子。用两当量的tBu 2Al-H处理8a导致H/F交换并形成tBu 2Al-F，其通过Si-F-Al和Al-F-Al桥与单体9a配位以形成六元SiCAlFAlF杂环。
Alkenylchlorosilanes functionalized by coordinatively unsaturated Al atoms, R′′(R′)Si(Cl)C(AltBu2)=C(H)R5[R =tBu,cHex, 1‐Ad, Ph, 3,5‐(F3C)2C6H3; R′ = Mes, Ph, 4‐tBuC6H4, 4‐tBuOC6H4, 4‐Et2NC6H4,tBu; R′′ = Mes, CH(SiMe3)2,tBu], were obtained in good yields by hydroalumination of the respective alkynylchlorosilanes R′′(R′)Si(Cl)C≡C‐R3withtBu2Al‐H. They feature four‐membered, close to planar SiCAlCl heterocycles by intramolecular Al–Cl interactions. The activation of the Si–Cl bonds results in bond lengthening from about 209 pm in3to 220 to 225 pm in compounds5. The29Si NMR resonances show an increasing shift to a lower field and range fromδ= 24.0 for5a[R =tBu, R′ = R′′ = Mes] toδ= 68.1 for5j[R = R′ = R′′ =tBu]. The latter value approaches those of solvent coordinated silyl cations such as Et3Si(C6H5Me)+. The related fluorides R′(tBuC≡C)Si(F)C(AltBu2)C = C(H)tBu9(R′ = Ph, Mes) were similarly obtained by hydroalumination of alkynylsilanes R′Si(F)(C≡C‐tBu)28. Compounds9are dimeric via Si–F–Al bridges and form eight‐membered C2Al2Si2F2heterocycles. The29Si NMR shifts ofδ= –4.7 and –14.7 and Si–F bond lengths of about 170 pm indicate the presence of four‐coordinate, covalently bound Si atoms. Treatment of8awith two equivalents oftBu2Al‐H led to H/F exchange and formation oftBu2Al‐F which is coordinated by monomeric9avia Si–F–Al and Al–F–Al bridges to form a six‐membered SiCAlFAlF heterocycle.