The intramolecular frustrated Lewis pair (mesityl)(2)P-CH(2)-CH(2)-B(C(6)F(5))(2) was generated in situ by HB(C(6)F(5))(2) hydroboration of dimesitylvinylphosphine. The compound reacts with 1-pentyne by C-H bond cleavage. It undergoes a 1,2-addition to the carbonyl group of trans-cinnamic aldehyde to yield a zwitterionic six-membered heterocycle by B-O and P-C bond formation. The Lewis pair regioselectively adds to the electron-rich C=C double bond of ethyl vinyl ether, and it selectively undergoes an exo-cis-2,3-addition to norbornene. A combined experimental/theoretical study suggests that this reaction takes place in an asynchronous concerted fashion with the B-C bond being formed in slight preference to the P-C bond. The addition products were characterized by X-ray crystal structure analyses.

The intramolecular vicinal frustrated P/B Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 readily abstracts a methyl anion equivalent from dimethylzirconocene to give the salt [Cp2ZrCH3](+) [Mes2PCH2CH2B(CH3)(C6F5)2](-) that features phosphane coordination to the zirconium cation. The analogous reaction between this FLP and Cp*2Zr(CH3)2 yields the analogous salt that, however, features a methyl bridged ([Zr]···H3C-[B]) tight ion pair structure. Both these products were characterized by X-ray diffraction. They both undergo 1,2-[Zr(+)]/P addition to carbon dioxide. The [Cp2ZrCH3](+) containing compound also adds to benzaldehyde or to p-tolyl isocyanate to give the respective [Zr(+)]/P addition products which were characterized by X-ray diffraction.

The reactive intramolecular frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 reacts rapidly with thionyl chloride to yield the zwitterionic chlorination product [Mes2PCl+]CH2–CH2[BCl(C6F5)2–]. Analogous zwitterionic products were obtained by the reaction of the FLP with chlorine or bromine. Compounds [Mes2PX+]CH2CH2[BX(C6F5)2–] (X = Cl, Br) were characterized by X‐ray crystal structure analyses.

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.