Access to Air-Stable 1,3-Diphosphacyclobutane-2,4-diyls by an Arylation Reaction with Arynes

Tuning of the physicochemical properties of the 1,3-diphosphacyclobutane-2,4-diyl unit is attractive in view of materials applications. The use of arynes is shown to be effective for installing relatively electron rich aryl substituents into the open-shell singlet P-heterocyclic system. Treatment of the sterically encumbered 1,3-diphosphacyclobuten-4-yl anion with ortho-silylated aryl triflates in the presence of fluoride under appropriate conditions afforded the corresponding 1-aryl 1,3-diphosphacyclobutane-2,4-diyls. The air-stable open-shell singlet P-heterocycles exhibit considerable electron-donating character, and the aromatic substituent influences the open-shell character, which is thought to be related to the property of p-type semiconductivity. The P-arylated 1,3-diphosphacyclobutane-2,4-diyl systems can be further utilized as detectors of hydrogen fluoride (HF), which causes a remarkable change in their photoabsorption properties.