Wang Lei, Fang Yong, Mao Haochuan, Qu Yi, Zuo Jiacheng, Zhang Zaichao, Tan Gengwen, Wang Xinping
State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, P. R. China.
School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huai'an, 223300, P. R. China.
Chemistry. 2017 May 17;23(28):6930-6936. doi: 10.1002/chem.201701308. Epub 2017 Apr 24.
Two new diboranes, 2,6-bis(BMes )mesitylene (1) and 3,3'-bis(BMes )bimesitylene (3), were synthesized. Two-electron reduction of 1 with elemental potassium afforded the C-H activation product [(18-c-6)K(THF) ] ⋅2 bearing a BC four-membered ring as colorless crystals, whereas the reduction of 3 with potassium led to the isolation of [(18-c-6)K(THF) ] ⋅3 as dark blue crystals. Both reduction products were characterized by structural and spectroscopic methods. Electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations revealed that the electron spin density of 3 mainly resides on the two boron nuclei and features a triplet ground state, which was confirmed by superconducting quantum interference device (SQUID) measurements as well as theoretical calculations. 3 represents the first structurally characterized boron-centered diradical with a triplet ground state. In addition, the reactivity of [(18-c-6)K(THF) ] ⋅3 toward PhSeSePh and nBu SnH was investigated, which is consistent with its radical character.
合成了两种新的乙硼烷，即2,6-双（硼甲基）均三甲苯（1）和3,3'-双（硼甲基）联均三甲苯（3）。用金属钾对1进行双电子还原得到C-H活化产物[（18-冠-6）钾（四氢呋喃）]·2，其含有一个硼碳四元环，呈无色晶体，而用钾还原3则得到深蓝色晶体[（18-冠-6）钾（四氢呋喃）]·3。两种还原产物均通过结构和光谱方法进行了表征。电子顺磁共振（EPR）光谱和理论计算表明，3的电子自旋密度主要位于两个硼原子核上，具有三重态基态，这一点通过超导量子干涉装置（SQUID）测量以及理论计算得到了证实。3是首个具有三重态基态且结构已表征的以硼为中心的双自由基。此外，还研究了[（18-冠-6）钾（四氢呋喃）]·3与二苯基二硒醚和正丁基锡烷的反应活性，这与其自由基性质相符。
