Study of the Air-Tolerant 1,3-Diphosphacyclobutane-2,4-diyl through the Direct Arylation.

Installing π-functional substituents on the skeletal phosphorus atoms of the air-tolerant 1,3-diphosphacyclobutane-2,4-diyl unit are promising for tuning the open-shell singlet P-heterocyclic chromophore. The sterically encumbered 1,3-diphosphaCycloButen-4-yl Anion (CBA), generated from the phosphorus-carbon triple bond, was available for the regioselective arylation via nucleophilic aromatic substitution (SN Ar) reaction, addition to arynes, and single-electron transfer (SET) process affording the corresponding P-arylated 1,3-diphosphacyclobutane-2,4-diyls. The photo-absorption and redox properties correlated with the effects of the aryl substituents on the 1,3-diphosphacyclobutane-2,4-diyl unit. The X-ray analyses enabled not only to discuss the metric parameters but also to visualize the radicalic electrons via the electron-density distribution analysis. The electron-donating character of the P-heterocyclic chromophores induced the p-type semiconductor behavior. Detection of hydrogen fluoride via formation of the 1λ5 ,3λ5 -diphosphete derivative was also developed.