作者:Miguel F. Silva Valverde、Peter Schweyen、Daria Gisinger、Thomas Bannenberg、Matthias Freytag、Christian Kleeberg、Matthias Tamm
DOI:10.1002/anie.201610903
日期:2017.1.19
with diarylboron halides (4‐R‐C6H4)2BX (R=H, X=Br; R=CH3, X=Cl; R=CF3, X=Cl) afforded the NHC‐stabilized borenium cations 10 a–c. Cyclic voltammetry revealed a linear correlation between the Hammett parameter σp of the para substituent and the half‐wave potential. Chemical reduction with decamethylcobaltocene, [(C5Me5)2Co], furnished the corresponding radicals 11 a–c; their characterization by EPR spectroscopy
三氟甲磺酸2-(三甲基甲硅烷基)咪唑鎓9与卤化二芳基硼化物(4-RC- 6 H 4)2 BX(R = H,X = Br; R = CH 3,X = Cl; R = CF 3, X = Cl)提供了NHC稳定的硼阳离子10 a – c。循环伏安法揭示哈米特参数之间的线性相关σ p的的对位取代基,且半波电位。用十甲基钴茂金属[[C 5 Me 5)2 Co]进行化学还原,得到相应的基团11 a – c; 通过EPR光谱对其进行表征,证实了11 a – c的顺磁特性,与硼同位素11 B和10 B具有较大的超精细耦合常数,而未成对电子向NHC的离域作用可忽略不计。用DFT计算卡宾(NHC)和硼基片段(BR 2)之间的自旋密度分布的百分比,得出11a – c的自旋密度比(BR 2 / NHC)为ca。9:1,这突出了它们独特的硼自由基特征。通过X射线衍射分析确定了最稳定的物质11 c的分子结构。