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

ABSTRACT: 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. The use of dehydrogenative coupling to build up catenatedstructures (molecular and polymeric) has become a highly topical area of main group chemistry. The newly developed dehydrogenative protocols are viable alternatives to the classical coupling strategies, such as salt eliminations. The growing interest in dehydrogenative coupling stems from the range of possibilities it opens up for new milder and more efficient syntheses of p-block element based materials. The potential is further strengthened by the amenability to catalysis, which is an aspect that received ample attention especially in the past decade.1 One of the main drivers of the dehydrogenative chemistry is its ability to generate unique new structures, such as the distinctive P16 macrocycle reported by Stephan.