Probing the Boundaries between Lewis‐Basic and Redox Behavior of a Parent Borylene. Issue 70 (11th November 2021) - Arrowsmith, Merle
Abstract: The parent borylene (CAAC)(Me3 P)BH, 1 (CAAC=cyclic alkyl(amino)carbene), acts both as a Lewis base and one‐electron reducing agent towards group 13 trichlorides (ECl3, E=B, Al, Ga, In), yielding the adducts 1‐ECl3 and increasing proportions of the radical cation [1] + for the heavier group 13 analogues. With boron trihalides (BX3, X=F, Cl, Br, I) 1 undergoes sequential adduct formation and halide abstraction reactions to yield borylboronium cations and shows an increasing tendency towards redox processes for the heavier halides. Calculations confirm that 1 acts as a strong Lewis base towards EX3 and show a marked increase in the B−E bond dissociation energies down both group 13 and the halide group. Abstract : Electrophile or nucleophile: A cyclic alkyl(amino)carbene‐ and PMe3 ‐stabilized parent borylene acts both as a Lewis base and reducing agent towards group 13 trihalides (EX3, E=B, Al, Ga, In, X=F, Cl, Br, I), yielding borylene‐EX3 adducts and the boryl radical cation. Halide abstraction converts the borylene‐BX3 adducts to the unsymmetrical borylboronium species. Computations probe the bond dissociation energy and electronic nature of the B–E bonds in the Lewis adducts.