Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

Cycloaddition reactions of the acyclic silylene Si­(SAriPr4)2 (AriPr4 = C6H3-2,6­(C6H3-2,6-iPr2)2) with a variety of alkenes and alkynes were investigated. Its reactions with the alkynes phenylacetylene and diphenylacetylene and the diene 2,3-dimethyl-1,3-butadiene yielded silacycles (AriPr4S)2Si­(CHCPh) (1), (AriPr4S)2Si­(PhCCPh) (2), and (AriPr4S)2SiCH2CMeCMeCH2 (3) at ambient temperature. The compounds were characterized by X-ray crystallography, 1H, 13C, and 29Si NMR spectroscopy, and IR spectroscopy. No reaction was observed with more substituted alkenes such as propene, (Z)-2-butene, tert-butylethylene, cyclopentene, 1-hexene, or the alkyne bis­(trimethylsilyl)­acetylene under the same reaction conditions. The germylene Ge­(SArMe6)2 and stannylene Sn­(SArMe6)2 (ArMe6 = C6H3-2,6­(C6H2-2,4,6-Me3)2) analogues of Si­(SArMe6)2 displayed no reaction with ethylene. Quantum chemical calculations using model tetrylenes E­(SPh)2 (E = Si, Ge, Sn; Ph = C6H5) show that cyclization reactions are endothermic in the case of germanium and tin derivatives but energetically favored for the silicon species.

本工作考察了无环亚硅基（acyclic silylene）Si(SAriPr4)2 [AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2]与各类烯烃、炔烃的环加成反应。该亚硅基与苯乙炔、二苯乙炔以及二烯2,3-二甲基-1,3-丁二烯在室温条件下发生反应，分别生成硅杂环化合物(AriPr4S)2Si(CH=CPh)（1）、(AriPr4S)2Si(PhC=CPh)（2）与(AriPr4S)2SiCH2CMeCMeCH2（3）。上述产物均通过X射线单晶衍射（X-ray crystallography）、1H、13C及29Si核磁共振波谱以及红外光谱完成表征。在相同反应条件下，该亚硅基与多取代烯烃（如丙烯、(Z)-2-丁烯、叔丁基乙烯、环戊烯、1-己烯）以及炔烃双(三甲基硅基)乙炔均未发生反应。与Si(SAriPr4)2结构类似的亚锗基Ge(SArMe6)2与亚锡基Sn(SArMe6)2 [ArMe6 = C6H3-2,6-(C6H2-2,4,6-Me3)2]，与乙烯均未发生反应。采用模型化第14族亚烷基（model tetrylenes）E(SPh)2（E = Si、Ge、Sn；Ph = C6H5）开展的量子化学计算结果表明：锗、锡衍生物的环加成反应为吸热过程，而硅衍生物的该类反应则在热力学上更具优势。