Isolable Anionic, Neutral and Cationic Radicals from Reactions ofN,N′‐Dimesityldiamidocarbene and Lewis Acids

Abstract

B(C6F5)3 undergoes nucleophilic attack by N,N′‐dimesityldiamidocarbene (DAC) with fluoride transfer to the boron center, resulting in a new zwitterion (1). This B−F fluoride can be replaced or abstracted to give the corresponding hydride (2) or triflate (3) derivatives or the corresponding cation (4). These species are reduced with KC8 or Cp2Co to give isolable anionic and neutral radicals (5–8). Similarly, the [Ph3C] cation undergoes nucleophilic attack by DAC resulting in the spontaneous formation of the radical cation (9).

Frustrated Radical Pairs: Insights from EPR Spectroscopy

“…Radical chemistry of FLPs containing boron Lewis acids and Group 14 Lewis bases such as carbenes or germylene have also been studied. Stephan et al, [22] demonstrated the reactivities of Lewis acidic boranes towards the nucleophilic carbene N,N'-dimesityldiamidocarbene (DAC) (Scheme 8). The reaction between DAC and B(C 6 F 5 ) 3 in benzene afforded a crystalline solid Me 2 C-(CONMes) 2 CC 6 F 4 BF(C 6 F 5 ) 2 in 80 % yield via nucleophilic attack of DAC to one of the para positions of a C 6 F 5 ring of B(C 6 F 5 ) 3 , followed by fluoride transfer to the boron center.…”

“…Stephan et al, [22] have also investigated the reactivities of the same trityl salt [Ph 3 C][B(C 6 F 5 ) 4 ] with the nucleophilic DAC carbene described earlier (Scheme 11, bottom). Nucleophilic attack of DAC at one of the para-positions of the trityl cation was observed, followed immediately with H 2 evolution to afford a cationic radical [Me 2 C(CONMes) 2 C C 6 H 4 CPh 2 C]C + (13) (Scheme 11, bottom).…”

Activation of C–F, Si–F, and S–F Bonds by N-Heterocyclic Carbenes and Their Isoelectronic Analogues

“…The reactivity of this type of zwitterionic adducts has been recently described by Stephan and co-workers utilizing a six-membered diamidocarbene. 55 Scheme 9 Unexpected C-F bond activation providing a zwitterionic adduct; Ar = DiPP…”

Frustrated Radical Pairs: Insights from EPR Spectroscopy

“…Stephan et al., [22] have also investigated the reactivities of the same trityl salt [Ph 3 C][B(C 6 F 5 ) 4 ] with the nucleophilic DAC carbene described earlier (Scheme 11, bottom). Nucleophilic attack of DAC at one of the para ‐positions of the trityl cation was observed, followed immediately with H 2 evolution to afford a cationic radical [Me 2 C(CONMes) 2 C C 6 H 4 CPh 2 C] .+ ( 13 ) (Scheme 11, bottom).…”

“…Theexciting preliminary outcomes from frustrated Lewis pair chemistry has drawn considerable interest in main group chemistry.Radical chemistry of FLPs containing boron Lewis acids and Group 14 Lewis bases such as carbenes or germylene have also been studied. Stephan et al, [22] demonstrated the reactivities of Lewis acidic boranes towards the nucleophilic carbene N,N'-dimesityldiamidocarbene (DAC) (Scheme 8). Ther eaction between DACa nd B(C 6 F 5 ) 3 in benzene afforded ac rystalline solid Me 2 C-(CONMes) 2 CC 6 F 4 BF(C 6 F 5 ) 2 in 80 %y ield via nucleophilic attack of DACt oo ne of the para positions of aC 6 F 5 ring of B(C 6 F 5 ) 3 ,f ollowed by fluoride transfer to the boron center.…”