Tris(pentafluorophenyl)alane

Selective Reduction of CO2 to CH4 by Tandem Hydrosilylation with Mixed Al/B Catalysts

“…As [B] was shown to be ineffective in catalyzing reduction of CO 2 via hydrosilylation, we turned our attention to [Al], a stronger LA based on several lines of experimental and theoretical evidence. , Most recently, we have revealed that the Al center of the even unsolvated Al­(C 6 F 5 ) 3 is not truly tricoordinated, but it adopts a dimeric structure with double Al···F­( ortho ) interactions in solid state . Such weak interactions are readily destroyed by addition of more electron-donating substrates than [Al] itself, such as toluene, ferrocene, or even fluorosilane and hydrosilane. ,, For instance, the unsolvated [Al] forms a stable and isolable adduct with Et 3 SiH in hexanes, while the interaction between [B] and Et 3 SiH could only be detected by indirect spectroscopic evidence .…”

“…In this context, it is of great interest and importance to survey suitable main-group LA candidates for effective CO 2 reduction. Inspired by the dual activation of CO 2 and silane R 3 SiH {[SiH]} by the above overviewed TM or TM/B­(C 6 F 5 ) 3 systems, we envisioned that a combination of the more oxophilic and higher Lewis acidic Al­(C 6 F 5 ) 3 {[Al]}, which could be sufficiently potent to render CO 2 fixation into silyl formate, with the less oxophilic B­(C 6 F 5 ) 3 {[B]}, which favors FLP-type [SiH] activation for subsequent steps of reduction, could serve as a main-group tandem FLP system that effectively converts CO 2 to CH 4 . The tunability of [Al]/[B] catalysts should allow us to develop more efficient, economical, and recyclable tandem LA catalysts based on inter- or intramolecular and heterogeneous platforms.…”

“…In this context, it is of great interest and importance to survey suitable main-group LA candidates for effective CO shown to be ineffective in catalyzing reduction of CO 2 via hydrosilylation, 29 we turned our attention to [Al], a stronger LA based on several lines of experimental and theoretical evidence. 27,30 Most recently, we have revealed that the Al center of the even unsolvated Al(C 6 F 5 ) 3 is not truly tricoordinated, but it adopts a dimeric structure with double Al•••F(ortho) interactions in solid state. 31 Such weak interactions are readily destroyed by addition of more electron-donating substrates than [Al] itself, such as toluene, ferrocene, or even fluorosilane and hydrosilane.…”

Polymerization of Polar Monomers Mediated by Main-Group Lewis Acid–Base Pairs

“…Replacing boron with aluminum in B­(C 6 F 5 ) 3 led to another widely applied LA, Al­(C 6 F 5 ) 3 . Al­(C 6 F 5 ) 3 can be prepared by ligand exchange between B­(C 6 F 5 ) 3 and AlMe 3 or AlEt 3 . − Several lines of evidence, as summarized by Chen in 2012, argued that Al­(C 6 F 5 ) 3 possesses higher Lewis acidity. More recently, the successful isolation of stable adducts with weak LBs such as Et 3 SiH and ferrocene with only Al­(C 6 F 5 ) 3 further supports this argument. , Suitable synthetic approaches toward LAs with enhanced acidity can be designed, but the challenge to maintain a completely undisturbed electron-accepting site might not be trivial, because such highly acidic species tend to seek stabilization even from their weakly basic environments, such as solvents, counterions, and their own ligands.…”

Elusive Silane–Alane Complex [SiH⋅⋅⋅Al]: Isolation, Characterization, and Multifaceted Frustrated Lewis Pair Type Catalysis

“…Almost 20 years after the original report, Piers and co-workers successfully isolated and structurally characterized the silane-borane adduct derived from Et 3 SiH and 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene,aperfluoroborole sophisticatedly tailored for higher Lewis acidity than B(C 6 F 5 ) 3 . [7] As compared with B(C 6 F 5 ) 3 ,the congener alane Al(C 6 F 5 ) 3 is as tronger LA [8] as gauged, for example,b yd ouble activation of bridged metallocene dimethyls, [9] fluoride ion affinity, [10] stable adduct formation with weakly basic arenes, [11] as well as by DFT calculations on the gas-phase Lewis acidity [12] and the enthalpy of ion-pair formation in solution for the methide abstraction reaction. [13] Despite its high Lewis acidity,the application of Al(C 6 F 5 ) 3 in the area of FLP studies is much less explored.…”