Isolable p- and m-[(tBu2MeSi)2Si]2C6H4: Disilaquinodimethane vs Triplet Bis(silyl radical)

Isomeric p- and m-disilaquinodimethanes 2 and 4 were synthesized by the reductive dehalogenation of the corresponding p- and m-bis(halosilyl)benzenes 1 and 3, respectively, and were isolated and structurally characterized. The X-ray diffraction and solid-state NMR studies of 2 revealed its singlet quinodimethane structure featuring two exocyclic SiC double bonds with some singlet biradical contribution. In contrast, the X-ray crystallography and EPR measurements of 4 disclosed its biradical nature, described as a triplet ground state bis(silyl radical).通过分别对相应的对位和间位双(卤硅基)苯1与3进行还原脱卤反应，成功合成了异构的对位与间位二硅代醌二甲烷（disilaquinodimethanes）2和4，并完成了分离与结构表征。对化合物2开展的X射线衍射（X-ray diffraction）与固态核磁共振（solid-state NMR）研究显示，其具有单重态醌二甲烷结构，包含两个环外Si=C双键，并表现出一定的单重态双自由基特征。与之相对，对化合物4的X射线晶体学（X-ray crystallography）与电子顺磁共振（EPR, Electron Paramagnetic Resonance）测试则揭示了其双自由基属性，该属性可被描述为三重态基态双(硅基自由基)。