Facile Intermolecular Aryl−F Bond Cleavage in the Presence of Aryl C−H Bonds: Is the η2-Arene Intermediate Bypassed?

The complex TpW(NO)(PMe3)(η2-benzene) cleanly inserts into the C−F bond of fluorobenzene to form the seven-coordinate complex TpW(NO)(PMe3)(F)(Ph) (confirmed by X-ray diffraction), while no C−H insertion is detected. Treatment of this product with triethyl- or phenyldimethylsilane results in liberation of benzene and the corresponding silyl fluoride. DFT calculations suggest a low-energy reaction pathway for C−F activation involving a fluorine-bound σ-complex that does not require the presence of an η2-arene intermediate. As the fluorine content of the benzene increases, or the benzene is replaced by fluoronaphthalene, C−F addition is no longer observed, and either C−H addition or η2-coordination dominates. Two species thought to be η2-silanes are also reported.

配合物TpW(NO)(PMe3)(η²-苯)可选择性地插入氟苯的碳氟（C−F）键，生成七配位配合物TpW(NO)(PMe3)(F)(Ph)（经X射线衍射（X-ray diffraction）确认），未检测到碳氢（C−H）插入产物。将该产物与三乙基硅烷或二甲基苯基硅烷反应，可释放出苯并得到相应的氟硅烷。密度泛函理论（Density Functional Theory, DFT）计算表明，碳氟键活化存在一条低能反应路径，该路径经由氟配位的σ配合物，无需η²-芳烃中间体参与。随着苯环上氟取代含量增加，或苯被氟萘取代时，不再观察到碳氟键加成反应，反应转而以碳氢键插入或η²-配位为主。另有研究报道了两种被认为是η²-硅烷的物种。