Pressure‐Induced Diels–Alder Reactions in C6H6‐C6F6 Cocrystal towards Graphane Structure

• Published in: Angewandte Chemie International Edition 2019-01, Vol.58 (5), p.1468-1473
• Main Authors: Wang, Yajie, Dong, Xiao, Tang, Xingyu, Zheng, Haiyan, Li, Kuo, Lin, Xiaohuan, Fang, Leiming, Sun, Guang'ai, Chen, Xiping, Xie, Lei, Bull, Craig L., Funnell, Nicholas P., Hattori, Takanori, Sano‐Furukawa, Asami, Chen, Jihua, Hensley, Dale K., Cody, George D., Ren, Yang, Lee, Hyun Hwi, Mao, Ho‐kwang
• Format: Article
• Language: English
• Subjects: Aromatic compounds; Benzene; Chemical reactions; Compressing; Crystal structure; cycloaddition; Diamonds; Diels-Alder reactions; Gas chromatography; graphane; Hydrocarbons; Neutron diffraction; Neutrons; Polymerization; Pressure; solid-state reactions; structure determination; Substitutes
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201813120

Pressure‐induced polymerization (PIP) of aromatics is a novel method for constructing sp3‐carbon frameworks, and nanothreads with diamond‐like structures were synthesized by compressing benzene and its derivatives. Here by compressing a benzene‐hexafluorobenzene cocrystal (CHCF), H‐F‐substituted graphane with a layered structure in the PIP product was identified. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by gas chromatography‐mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, and leads to a [4+2] polymer, which then transforms to short‐range ordered H‐F‐substituted graphane. The reaction process involves [4+2] Diels–Alder, retro‐Diels–Alder, and 1‐1′ coupling reactions, and the former is the key reaction in the PIP. These studies confirm the elemental reactions of PIP of CHCF for the first time, and provide insight into the PIP of aromatics. Short‐range ordered H,F‐substituted graphane was obtained by compressing benzene and hexafluorobenzene cocrystals. By using neutron diffraction and GC‐MS, the reaction process and elementary reactions were identified. The reaction process involves [4+2]Diels–Alder, retro‐Diels–Alder, and 1‐1′ coupling reactions, and the Diels–Alder reaction is the key reaction in the polymerization process.