Geometrically Enforced Donor-Facilitated Dehydrocoupling Leading to an Isolable Arsanylidine-Phosphorane

A proximate Lewis
basic group facilitates the mild dehydrogenative
P–As 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.