Isolable Diphosphorus-Centered Radical Anion and Diradical Dianion

Two salts containing diphosphorus-centered radical anion 1•– and diradical dianion 12–•• were obtained by one- and two-electron reductions of an indenofluorene-bridging diphosphaalkene (1) with K and KC8, respectively. The salts have been characterized by electron paramagnetic resonance (EPR) spectroscopy, UV–vis absorption spectroscopy, and single-crystal X-ray diffraction analysis. EPR spectroscopy and theoretical calculations reveal that the spin density of the radicals mainly resides on the phosphorus atoms, and 12–•• has an open-shell singlet ground state. 1•– and 12–•• represent the first isolable and structurally characterized diphosphorus-centered radical anion and dianion.