Geometrically enforced donor-facilitated dehydrocoupling leading to an isolable arsanylidine-phosphorane

A proximate Lewis basic group facilitates the mild dehydrogenative PAs intramolecular coupling in the phosphine-arsine peri-substituted acenaphthene 3, affording thermally and hydrolytically stable arsanylidine- phosphorane 4 with a sterically accessible two-coordinate arsenic atom. The formation of 4 is thermoneutral due to the dehydrogenation being concerted with the donor coordination. Reaction of 4 with a limited amount of oxygen reveals arsinidene-like reactivity via formation of cyclooligoarsines, supporting the formulation of the bonding in 4 as base-stabilized arsinidene R3P→AsR.