乙硅烯的可分离阳离子自由基：合成、表征及可逆单电子氧化还原体系

The isolable cation radical of disilene: synthesis, characterization, and a reversible one-electron redox system.

作者信息

Inoue Shigeyoshi, Ichinohe Masaaki, Sekiguchi Akira

机构信息

Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.

出版信息

J Am Chem Soc. 2008 May 14;130(19):6078-9. doi: 10.1021/ja801761w. Epub 2008 Apr 19.

DOI:10.1021/ja801761w

PMID:18422315

Abstract

The highly twisted tetrakis(di-tert-butylmethylsilyl)disilene 1 was treated with Ph3C+.BAr4- (BAr4-: TPFPB = tetrakis(pentafluorophenyl)borate) in toluene, producing disilene cation radical 3 upon one-electron oxidation. Cation radical 3 was isolated in the form of its borate salt as extremely air- and moisture-sensitive red-brown crystals. The molecular structure of 3 was established by X-ray crystallography, which showed a highly twisted structure (twisting angle of 64.9 degrees) along the central Si-Si bond with a bond length of 2.307(2) A, which is 2.1% elongated relative to that of 1. The cation radical is stabilized by sigma-pi hyperconjugation by the four tBu2MeSi groups attached to the two central sp2-Si atoms. An electron paramagnetic resonance (EPR) study of the hyperfine coupling constants (hfcc) of the 29Si nuclei indicates delocalization of the spin over the central two Si atoms. A reversible one-electron redox system between disilene, cation radical, and anion radical is also reported.

摘要

将高度扭曲的四（二叔丁基甲基硅基）二硅烯1在甲苯中用三苯基碳正离子四（五氟苯基）硼酸盐（BAr4-：TPFPB）处理，经单电子氧化生成二硅烯阳离子自由基3。阳离子自由基3以其硼酸盐的形式被分离出来，为对空气和水分极度敏感的红棕色晶体。通过X射线晶体学确定了3的分子结构，结果表明其沿着中心Si-Si键具有高度扭曲的结构（扭曲角为64.9度），键长为2.307(2) Å，相对于1伸长了2.1%。该阳离子自由基通过连接在两个中心sp2-Si原子上的四个tBu2MeSi基团的σ-π超共轭作用得以稳定。对29Si核的超精细偶合常数（hfcc）进行的电子顺磁共振（EPR）研究表明，自旋在中心的两个Si原子上离域。还报道了二硅烯、阳离子自由基和阴离子自由基之间的可逆单电子氧化还原体系。