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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Combined Experimental and Theoretical Study on the Formation of the Elusive 2-Methyl-1-silacycloprop-2-enylidene Molecule under Single Collision Conditions via Reactions of the Silylidyne Radical (SiH; X-2 Pi) with Allene (H2CCCH2; X(1)A(1)) and D4-Allene (D2CCCD2; X(1)A(1))
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Combined Experimental and Theoretical Study on the Formation of the Elusive 2-Methyl-1-silacycloprop-2-enylidene Molecule under Single Collision Conditions via Reactions of the Silylidyne Radical (SiH; X-2 Pi) with Allene (H2CCCH2; X(1)A(1)) and D4-Allene (D2CCCD2; X(1)A(1))

机译：通过单硅烷基自由基（SiH; X-2 Pi）与丙二烯（H2CCCH2; X（1））反应在单碰撞条件下形成难以捉摸的2-甲基-1-硅环丙-2-烯基亚烷基分子的实验和理论研究相结合A（1））和D4-Allene（D2CCCD2; X（1）A（1））

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The crossed molecular beam reactions of the ground-state silylidyne radical (SiH; X-2 Pi) with allene (H2CCCH2; X(1)A(1)) and D4-allene (D2CCCD2; X(1)A(1)) were carried out at collision energies of 30 kJ mol(-1). Electronic structure calculations propose that the reaction of silylidyne with allene has no entrance barrier and is initiated by silylidyne addition to the pi electron density of allene either to one carbon atom (C1/C2) or to both carbon atoms simultaneously via indirect (complex forming) reaction dynamics. The initially formed addition complexes isomerize via two distinct reaction pathways, both leading eventually to a cyclic SiC3H5 intermediate. The latter decomposes through a loose exit transition state via an atomic hydrogen loss perpendicularly to the plane of the decomposing complex (sideways scattering) in an overall exoergic reaction (experimentally: -19 +/- 13 kJ mol(-1) computationally: -5 +/- 3 kJ mol(-1)). This hydrogen loss yields the hitherto elusive 2-methyl-1-silacycloprop-2-enylidene molecule (c-SiC3H4), which can be derived from the closed-shell cyclopropenylidene molecule (c-C3H2) by replacing a hydrogen atom with a methyl group and the carbene carbon atom by the isovalent silicon atom. The synthesis of the 2-methyl-1-silacydoprop-2-enylidene molecule in the bimolecular gas-phase reaction of silylidyne with allene enriches our understanding toward the formation of organosilicon species in the gas phase of the interstellar medium in particular via exoergic reactions of no entrance barrier. This facile route to 2-methyl-1-silacycloprop-2-enylidene via a silylidyne radical reaction with allene opens up a versatile approach to form hitherto poorly Characterized silicon-bearing species in extraterrestrial environments; this reaction class might represent the missing link, leading from silicon-bearing radicals via organosilicon chemistry eventually to silicon carbon-rich interstellar grains even in cold molecular clouds where temperatures are as low as 10 K.
机译：基态甲硅烷基（SiH; X-2 Pi）与丙二烯（H2CCCH2; X（1）A（1））和D4-丙二烯（D2CCCD2; X（1）A（1））的交叉分子束反应在30 kJ mol（-1）的碰撞能量下进行。电子结构计算表明，甲硅烷基炔与丙二烯的反应没有入口壁垒，并且是通过甲硅烷基丙二烯的π电子密度加到一个碳原子（C1 / C2）或同时通过间接（复合形成）同时加到两个碳原子上而引发的反应动力学。最初形成的加成配合物通过两个不同的反应途径异构化，最终都形成环状SiC3H5中间体。后者在整个放热反应中通过垂直于分解复合物平面（横向散射）的氢原子损失通过松散的出口过渡态分解（实验上：-19 +/- 13 kJ mol（-1）计算：-5 +/- 3 kJ mol（-1））。这种氢的损失产生了迄今难以捉摸的2-甲基-1-硅环丙-2-烯基分子（c-SiC3H4），该分子可以通过将氢原子替换为甲基而衍生自闭壳环丙烯基分子（c-C3H2）。卡宾碳原子由等价硅原子构成。在甲硅烷基乙炔与丙二烯的双分子气相反应中合成2-甲基-1-甲硅烷基丙-2-烯基分子，特别是通过星云的热能反应，丰富了我们对星际介质气相中有机硅物质形成的理解。没有入口障碍。这种通过甲硅烷基与甲硅烷基进行甲硅烷基自由基反应而生成2-甲基-1-硅环丙-2-烯基的简便途径，为在地球外环境中形成迄今表征欠佳的含硅物种开辟了一种通用方法。该反应类别可能代表了缺失的环节，甚至是在温度低至10 K的寒冷分子云中，从含硅自由基通过有机硅化学反应最终到富含硅碳的星际晶粒。

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