Lu Xin, Wang Xinlan, Yuan Qinghong, Zhang Qianer
State Key Laboratory for Physical Chemistry of Solid Surfaces and Center for Theoretical Chemistry, Department of Chemistry, Xiamen University, Xiamen 361005, China.
J Am Chem Soc. 2003 Jul 2;125(26):7923-9. doi: 10.1021/ja035329+.
The cycloaddition chemistry of several representative unsaturated hydrocarbons (1,3-butadiene, benzene, ethylene, and acetylene) and a heterocyclic aromatic (thiophene) on a Si(111)-7x7 surface has been explored by means of density functional cluster model calculations. It is shown that (i) 1,3-butadiene, benzene, and thiophene can undergo both [4+2]-like and [2+2]-like cycloadditions onto a rest atom-adatom pair, with the former process being favored over the latter both thermodynamically and kinetically; (ii) ethylene and acetylene undergo [2+2] cycloaddition-like chemisorptions onto a rest atom-adatom pair; and (iii) all of these reactions adopt diradical mechanisms. This is in contrast to the [4+2] cycloaddition-like chemisorptions of conjugated dienes on a Si(100) surface and to the prototype [4+2] cycloadditions in organic chemistry, which were believed to adopt concerted reaction pathways. Of particular interest is the [4+2]-like cycloaddition of s-trans-1,3-butadiene, whose stereochemistry is retained during its chemisorption on the Si(111) surface.
通过密度泛函簇模型计算，研究了几种代表性不饱和烃（1,3 - 丁二烯、苯、乙烯和乙炔）以及一种杂环芳烃（噻吩）在Si(111)-7x7表面的环加成化学。结果表明：（i）1,3 - 丁二烯、苯和噻吩能够在一个静止原子 - 吸附原子对发生类似[4 + 2]和类似[2 + 2]的环加成反应，前者在热力学和动力学上都比后者更有利；（ii）乙烯和乙炔在一个静止原子 - 吸附原子对发生类似[2 + 2]环加成的化学吸附；（iii）所有这些反应都采用双自由基机制。这与共轭二烯在Si(100)表面的类似[4 + 2]环加成化学吸附以及有机化学中的原型[
