Triplet Phenylarsinidene and Its Oxidation to Dioxophenylarsine

Diradicals are key intermediates involved in numerous chemical processes and have attracted considerable attention in synthetic chemistry, biochemistry, and materials science. Even though parent arsinidene (H-As) has been characterized well, the high reactivity of subsituted arsinidenes has prohibited their isolation and characterization to date. Here, we report the preparation of triplet phenylarsinidene through the photolysis of phenylarsenic diazide, isolated in an argon matrix, and its subsequent characterization by infrared and UV/Vis spectroscopy. Doping the matrices containing phenylarsinidene with molecular oxygen leads to the formation of hitherto unknown anti-dioxyphenylarsine. The latter undergoes isomerization to novel dioxophenylarsine upon 465 nm irradiation. The assignments were validated by isotope-labeling experiments combined with B3LYP/def2-TZVP computations.