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Hypervalent (three-center, four-electron) bonding in organobismuth complexes has demonstrated to activate bonds and perturb electron configurations promoting synthesis, catalysis, materials, and other applications. 

In order to stabilize a 10–P–3 species with C 2v 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 C s -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 3 -hybridized benzylic carbon atoms would prevent the formation of aromatic P-heterocycles. However, subjecting 1 to a metalation/phosphination/reduction sequence afforded cyclotriphosphane 3, resulting from trimerization of the P( i ) center unbound by its oxygen donors. Pincer 2 featuring four benzylic CF 3 groups was expected to strengthen the O–P–O bond of the target, but after metal–halogen exchange and quenching with PCl 3 , unexpected cyclization with loss of CH 3 Cl was observed to give monochlorinated 5. Treatment of 5 with ( p -CH 3 )C 6 H 4 MgBr generated crystalline P-( p -Tol) derivative 6, which was characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. The complex 19 F NMR spectra of 5 and 6 observed experimentally, were reproduced by simulations with MestreNova.