Matrix Isolation of the Arsinoborene FB-As═BF with an As═B Double Bond Character.

We report on the generation of FB-As═BF, an arsinoborene (boranylidenearsane) with a genuine As═B double bond, where both the As and B atoms are two-coordinate. It was obtained from the reaction of AsF with laser-ablated boron atoms under cryogenic conditions in neon and argon matrices. In addition, the single-bonded arsenic-boron radicals FB-AsF and FB-AsF were characterized. These species were identified by infrared spectroscopy and B isotope substitution in conjunction with quantum-chemical calculations at the B3LYP and CCSD(T) levels of theory. The isomerization from FB-AsF to FB-AsF can be triggered by irradiation with ultraviolet light (λ = 275 nm) in argon. This discovery of the arsinoborene FB-As═BF further extends the series of multiple-bonded systems between heavy main group elements and boron.