Indirect synthesis of a pair of formal methane activation products at a phosphane/borane frustrated Lewis pair.

The regioisomeric formal MesPCHCHB(CF) FLP methane splitting products MesP(H)CHCHB(CH)(CF) and MesP(CH)CHCHB(H)(CF) were produced by indirect stepwise reactions. They were stable at 60 °C and were both characterized by X-ray diffraction. A DFT analysis revealed that their formation from the FLP and CH would be endergonic by +6.9 and +3.6 kcal mol, respectively, and it indicated that methane elimination from the zwitterionic products is kinetically hindered by barriers of 54.0 and 72.3 kcal mol, respectively.