PB₁₂⁺ and P₂B₁₂^+/0/-: The Novel B₁₂ Cage Doped by Nonmetallic P Atoms

A new kind of nonmetallic atom-doped boron cluster is described herein theoretically. When a phosphorus atom is added to the B₁₂ motif and loses an electron, a novel B₁₂ cage is obtained, composed of two B₃ rings at both ends and one B₆ ring in the middle, forming a triangular bifrustum. Interestingly, this B₁₂ cage is formed by three B₇ units joined together from three directions at an angle of 120°. When two P atoms are added to the B₁₂ motif, this novel B₁₂ cage is also obtained, and two P atoms are attached to the B₃ rings at both ends of the triangular bifrustum, forming a triangular bipyramid (Johnson solid). Amazingly, the global minimums of neutral, monocationic, and monoanionic P₂B₁₂^+/0/- have the same cage structure with a D₃ symmetry; this is the smallest boron cage with the same structure. The P atom has five valence electrons, according to adaptive natural density partitioning bonding analyses of cage PB₁₂⁺ and P₂B₁₂, in addition to one lone pair, the other three electrons of the P atom combine with an electron of each B atom on the B₃ ring to form three 2c-2e σ bonds and form three electron sharing bonds with B atoms through covalent interactions, stabilizing the B₁₂ cage. The calculated photoelectron spectra can be compared with future experimental values and provide a theoretical basis for the identification and confirmation of PB₁₂^- (n = 1-2).