Electrophilic Activation of Lewis Base Complexes of Borane with Trityl Tetrakis(pentafluorophenyl)borate

Abstract

Borenium ions do not accumulate under the conditions of hydride abstraction from Lewis base borane complexes (L·BH3) using trityl cation because subsequent rapid reaction with L·BH3 occurs to form B−H−B bonds. The hydride-bridged cations are sufficiently stabilized to resist abstraction of the remaining hydride by excess trityl cation; however, reversible cleavage of the 3c2e bond does take place to release borenium ion equivalents, as evidenced by interaction with weak nucleophiles.

Lewis Superacidic Ionic Liquids with Tricoordinate Borenium Cations

“…[9,22] Similarly, the main signal at 36±1 ppm and shoulder ca. 45.5 ppm for P888-BCl3-2MCl3 systems is consistent with [BCl2{P888}] + [23] and BCl3. Partial ligand transfer onto a metal centre was confirmed with 27 Al NMR spectroscopy (Figure 3-SI, [24][25][26] with a shoulder at 75±1 ppm, originating from a pentacoordinate complex, [AlCl3L2], and/or cationic complex, [AlCl2L2] + .…”

Superelectrophilic Intermediates in Nitrogen-Directed Aromatic Borylation

“…3). 20 The 3c2e bond in 12 increases electron density at boron compared to the borenium ion 11 , but 12 is a capable electrophile nevertheless, and undergoes bonding interactions with weak nucleophiles including triflate and bistriflimidate anions, trialkylsilanes, and dichloromethane.…”

Fundamental and Applied Properties of Borocations

“…The avoidance of strongly coordinating solvents and the use of a solvent that is stable towards cationic boron electrophiles are obviously essential requirements for harnessing borenium ion reactivity in solution. Whilst ethers unsurprisingly decompose in the presence of many borocations [22,23], even CH 2 Cl 2 will react with certain borocations [24]. One specific example is from attempts to form [(amine) [25].…”