Trimerization and cyclization of reactive P-functionalities confined within OCO pincers.

In order to stabilize a 10-P-3 species with symmetry and two lone pairs on the central phosphorus atom, a specialized ligand is required. Using an NCN pincer, previous efforts to enforce this planarized geometry at P resulted in the formation of a -symmetric, 10π-electron benzazaphosphole that existed as a dynamic "bell-clapper" in solution. Here, OCO pincers 1 and 2 were synthesized, operating under the hypothesis that the more electron-withdrawing oxygen donors would better stabilize the 3-center, 4-electron O-P-O bond of the 10-P-3 target and the sp-hybridized benzylic carbon atoms would prevent the formation of aromatic P-heterocycles.