Density functional and complete active space (CAS) SCF and CASPT2 calculations have been performed to investigate structural and electronic features of p-phenylbisphosphinidene and the analogous p-phenylbisnitrene, p-phenylbismethylene, p-phenylbis(fluoromethylene), and p-phenylbis(chloromethylene) molecules. Similar to the other species investigated, with the exception of p-phenylbis(fluoromethylene), p-phenylbisphosphinidene exhibits an open-shell singlet diradical ground state with a quinone-like structure. The singlet-triplet energy gap, computed with CASPT2 on CASSCF(10,10)/6-31+G* optimized structures, amounts to 1.78 kcal/mol. At the DFT (B3LYP/6-31+G*) level a value of 5.14 kcal/mol is obtained. Due to the highly multiconfigurational character of the p-phenylbisphosphinidene singlet and triplet wave functions, the DFT treatment becomes less accurate. Going to p-phenylbisnitrene, p-phenylbis(chloromethylene), p-phenylbis(fluoromethylene), and p-phenylbismethylene energies are better described by DFT calculations as the triplet wave functions have only one and the singlet wave functions exactly two leading configurations. The calculated singlet-triplet energy gaps are found to lie in a range of 1.3-2.2 kcal/mol at both DFT and CASPT2 levels of theory. p-Phenylbis(fluoromethylene) is a special case in the series as it has a closed-shell singlet ground state. The multiconfigurational treatment shows, however, that the singlet diradical state is very close in energy to the closed-shell singlet, even though the stability of the diradical is somewhat overemphasized by this method. The relative energies and the respective IR spectra are also discussed.