Simple Access to the Non‐Oxidizing Lewis Superacid PhF→Al(OR^F)₃ (R^F=C(CF₃)₃)

Tris(perfluorotolyl)borane—A Boron Lewis Superacid

“…[21] Attempts to prepare bis(2,3,5,6-tetrafluoro-4-trifluoromethyl)borane,H B(p-C 6 F 4 CF 3 ) 2 ,b ye mploying the standard method [22] There is still no experimental structure for BCF,b ut crystals of BTolF for X-ray diffraction experiments were grown from ac oncentrated solution in n-hexane at À30 8 8C. We determined structures of the free molecules of BTolF and BCF in the gas-phase by electron diffraction (GED) using the diffractometer at Bielefeld University [24,25] (details see Supporting Information).…”

Synthesis and oxidation of hexafluoroisopropoxyborylferrocenes

“…To combine a decent stability with sufficient Lewis acidity, we chose the fluorinated alkoxide 1,1,1,3,3,3-hexafluoro-2-propoxy ligand (Ohfip) for the boryl residue. The Ohfip-ligand was proven to provide suitable Lewis acidity to an electron-deficient central atom, e.g., in the related B(Ohfip) 3 , as well as in monomeric Al[OC(CF 3 ) 3 ] 3 or dimeric Al 2 (Ohfip) 6 [30][31][32][33][34]. Carpenter and coworkers suggested that oxidation enhances the Lewis acidity of ferrocenylboranes, so that the B center in certain borylferrocinium compounds abstracts a fluoride from a [BF 4 ] -counteranion [35].…”

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

“…This intermolecular Al···F interaction also leads to an extended structure featuring aherringbone pattern for the SiÀH···Al···F motif (Figure 2). It is worth noting that such as econdary intermolecular interaction is also present in PhF·Al(OC(CF 3 ) 3 ) 3 (Al···F: 2.770(8) ), [10] . [18] In the present case,E t 3 SiH, as aw eak LB,i sn ot electron-donating enough to effectively stabilize the unsolvated Al(C 6 F 5 ) 3 so it seeks for additional stabilization by interacting with afluorine atom from asecond molecule.Incomparison, the geometry at the Al center in the F-bridged complex, [Et 3 SiÀF···Al(C 6 F 5 ) 3 ], features more pronounced pyramidalization, with aS i-F distance of 1.725 (2) , an Al···F contact of 1.841 (2) , and a AE C-Al-C of 348.18 8,a ll of which are averaged from three independent molecules (see Figure S22 in the Supporting Information).…”

“…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.…”

“…[17] Moreover,Krossing and co-workers noted that the analogous aluminum super LA [Al{OC(CF 3 ) 3 } 3 ]f orms stable adducts with PhF and Me 3 SiF. [10] Interestingly,the fluorosilane adduct [Me 3 Si À F···Al{OC(CF 3 ) 3 } 3 ]was viewed as aJ anus-like bifunctional LA with as oft electrophilic Si site and ah ard electrophilic Al site for different substrates. [18] We hypothesized that, as ar esult of the demonstrated superior Lewis acidity and activity in many catalytic reactions by the alane compared to the borane,Al(C 6 F 5 ) 3 could lead to the isolable and characterizable simple silane-alane complex [R 3 Si À H···Al(C 6 F 5 ) 3 ], and thus uncover its potentially unique catalytic utilities.Inthis context, we communicate herein the isolation and structural characterization of silane-alane complexes with ah ydride or fluoride bridge.E xcitingly,t he silane-alane complex effectively catalyzes (or is involved in) avariety of transformations,including four different types of catalytic reactions:l igand redistribution of silanes,p olymerization of polar alkenes,h ydrosilylation of unactivated alkenes,and hydrodefluorination of fluoroalkanes.…”