A Linear Di-coordinate Boron Radical Cation

Abstract The pursuit of di-coordinate boron radical has been continued for more than a half century with no irrefutable experimental evidence. Through stabilizing the two reactive atomic orbitals of the central boron atom by two orthogonal p-donating and p-accepting functionalities, a linear di-coordinate boron radical cation [3][B(C6F5)4] is isolated and structurally characterized. The electron deficient radical cation undergoes facile one-electron reduction to borylene and binds Lewis base to give heteroleptic tri-coordinate boron radical cation. The co-existence of half-filled and empty p orbitals at boron also allows the CO-regulated electron transfer to be explored. As the introduction of CO promotes the electron transfer from tri-coordinate neutral boron radical (2•) to boron radical cation ([8]+•), the removal of CO under vacuum furnishes the reverse electron transfer from borylene (4) to [1]+ to yield a solution consisting of two boron radicals, 2• and [3]+•.