Dehydrohalogenation of halobenzenes and C(sp3)-X (X = F, OPh) bond activation by a molecular calcium hydride

The molecular calcium hydride, [(BDI)CaH]2 (BDI = HC{(Me)CN-2,6-i-Pr2C6H3}2), effects the slow hydrodehalogenation of C6H5X (X I, Br) to provide benzene and respective dimeric halides, [(BDI)CaX]2. Although a similar reaction with fluorobenzene was non-discriminating, analogous hydrogenation chlorobenzene observed, albeit this process yields hydride-chloride as alkaline earth-containing product. Assessment bromide- chloride-based processes by density functional theory (DFT) calculations, imply that reactions take place retention structures throughout. Both systems invoke an SNAr-type displacement halide, via barriers (in range 32–34 kcal mol?1 for C6H5Br 31.1–32.9 C6H5Cl), which vary only marginally during transformation initial hydride halide-hydride intermediates. isolation is ascribed, therefore, its more rapid crystallisation depletion from solution. Also reported reactivity ?,?,?-trifluorotoluene anisole, yield corresponding dicalcium hydride-fluoride phenoxide derivatives, respectively, rather than products directed ortho metalation.