Scope and Mechanisms of Frustrated Lewis Pair Catalyzed Hydrogenation Reactions of Electron‐Deficient CC Double Bonds

Abstract

Several phosphonium and ammonium triarylborohydrides, which are intermediates in hydrogenation reactions catalyzed by frustrated Lewis pairs, were synthesized in high yield under mild conditions from triaryl boranes, ammonium or phosphonium halides, and triethylsilane. The kinetics and mechanisms of the reactions of these hydridoborate salts with benzhydrylium ions, iminium ions, quinone methides, and Michael acceptors were investigated, and their nucleophilicity was determined and compared with that of other hydride donors.

Heterolytic Si−H Bond Cleavage at a Molybdenum‐Oxido‐Based Lewis Pair

“…Additionally, 11 B NMR spectroscopy of Int 3 a’ in CD 2 Cl 2 revealed the disappearance of the doublet corresponding to the borohydride moiety of 3 a (−25.4 ppm) and a new sharp singlet at −2.7 ppm, matching literature data for the [PhCH 2 OB(C 6 F 5 ) 3 ] − anion (Figure S8) …”

“…The resulting 1 H NMR spectrum revealed the ‐(CHD)‐ methylene resonance integrating for only one proton, compared to two in the non‐deuterated compound (Figure S9). Additionally, the corresponding 13 C NMR spectrum showed resonances for the aromatic benzylate protons in agreement with literature as well as a triplet for the ‐(CHD)‐ moiety ( 1 J (C−D) ≈21 Hz), confirming insertion into the B−D bond (Figure S10) …”

“…We found that treatment of Na[HB(C 6 F 5 ) 3 ] or [NBu 4 ][HB(C 6 F 5 ) 3 ] with [Ph 3 C][BF 4 ] also lead to the formation of triphenylmethane and 19 F NMR spectroscopy revealed new sets of signals (−140.2, −157.8, −163.6, −199.1 ppm for the Na + salt and −136.3, −162.1, −166.7, −191.1 ppm for the [NBu 4 ] + compound) suggesting a similar fluoride transfer. These data are different to those found for 4 a and 4 b , but comparable to those of [NEt 4 ][FB(C 6 F 5 ) 3 ], indicating that the fluoride transfer occurs independently of the used cation.…”

Solid frustrated-Lewis-pair catalysts constructed by regulations on surface defects of porous nanorods of CeO2

“…Hydrogen activation by either transition metal complexes or metal-based heterogeneous catalysts have been well developed and successfully applied for various reactions4. Recently, frustrated Lewis pairs (FLPs), Lewis acids and bases that are sterically prevented from interaction to form Lewis acid–base adjuncts, can efficiently and cooperatively activate many small molecules (for example, H 2 , CO 2 , and NO) and even strong C–H bond for important catalytic reactions including hydrogenation, hydroamination and carbon dioxide reduction5678910111213141516171819202122232425.…”

Synthesis of a Perfluorinated Phenoxyphosphorane and Conversion to Its Hexacoordinate Anions

“…The PÀOb ond lengths in 3 are significantly greater than the corresponding values in 1,c onsistent with the trans influence exertedb yt he substituents in the octahedral geometry.T he PÀFb ond length of 1.619(1) in 3 is longer than the value observed in [NMe 4 ][PF 6 ]( 1.568-1.592 ), but comparable to the values observed in the [F 2 P(CN) 4 ] À anion [1.591(2)-1.603 (2) ]. [18] The structure of 3 also contains one O···H [2.661(3) ], one meta-F···H [2.539(3) ], and two ortho-F···H [2.554(4), 2.658(4) ]i nter-ion bonding interactions. (2) ].…”