Bis(silylene)‐Induced Conversion of Yellow Arsenic

Despite their structural similarity, the controlled conversion of elemental arsenic remains significantly less investigated than that of its lighter congener phosphorus. Exploring how As 4 responds to low‐valent main‐group compounds is therefore essential to understand differences in bonding and reactivity across the heavier pnictogens. The reactivity of N,N‐bis(silylenyl)aniline ((LSi) 2 NPh) (L = PhC(N t Bu) 2 ) toward yellow arsenic (As 4 ) has been explored, revealing unprecedented arsasila‐cycles. Under strict light‐excluding conditions, a selective conversion of As 4 with (LSi) 2 NPh into the first 2,5‐disila‐3,4‐diarsapyrrole, [(LSi) 2 (NPh)As 2 ] ( 1 ), featuring two SiAs double bonds is observed. Irradiation of 1 induces dimerization and ring contraction to [(LSi)(NPh)AsSi] 2 L 2 (L 2 = [PhC(N t Bu) 2 ] 2 ) ( 2 ), accompanied by the formation of gray arsenic. Compound 2 reacts with untreated glass surfaces to give [(LSi)(NPh)As(L H Si)] (L H = PhCH(N t Bu) 2 ) ( 3 ), retaining the four‐membered heterocycle. Variation of stoichiometry between 1 and As 4 affords the six‐membered heterocycle [(LSi) 2 (NPh)As 2 (LSi)] ( 4 ) and the four‐membered heterocycle [(LSiH) 2 (NPh) 2 ] ( 5 ). The product distribution can be directed by controlling light exposure, stoichiometry, temperature, and vessel surface, highlighting the distinctive structural rearrangements and enhanced reactivity of arsenic compared to phosphorus.