Stability of B₁₂(CN)₁₂²⁻: Implications for Lithium and Magnesium Ion Batteries

Abstract

Multiply charged negative ions are seldom stable in the gas phase. Electrostatic repulsion leads either to autodetachment of electrons or fragmentation of the parent ion. With a binding energy of the second electron at 0.9 eV, B12 H12 (2-) is a classic example of a stable dianion. It is shown here that ligand substitution can lead to unusually stable multiply charged anions. For example, dodecacyanododecaborate, B12 (CN)12 (2-) , created by substituting H by CN is found to be highly stable with the second electron bound by 5.3 eV, which is six times larger than that in the B12 H12 (2-) . Equally important is the observation that CB11 (CN)12 (2-) , which contains one electron more than needed to satisfy the Wade-Mingos rule, is also stable with its second electron bound by 1.1 eV, while CB11 H12 (2-) is unstable. The ability to stabilize multiply charged anions in the gas phase by ligand manipulation opens a new door for multiply charged species with potential applications as halogen-free electrolytes in ion batteries.

Superhalogen and Superacid

“…Its anion is formed by a carborane cage surrounded with fluorine atoms and shows superhalogenic behavior. A similar structure with cyano groups, B 12 (CN) 12 2− , was suggested as a highly stable dianion with second electron bound by 5.3 eV …”

Colossal Stability of Gas‐Phase Trianions: Super‐Pnictogens

“…Instead of using only the octet rule,w eu sed multiple electron counting rules simultaneously;n amely,t he octet and Wade-Mingos rules. B 12 [11] showed that B 12 (CN) 12 2À is more stable than its monoanion and it takes 5.3 eV to eject the second electron. [10] According to the Wade-Mingos rule,( n + 1) pairs of electrons are required to stabilize aborane cage where n is the number of vertices in the boron polyhedron.…”

“…Here E is the total energy corresponding to the ground-state structure.T he FEA, SEA, and TEA for BeB 11 is strongly stable against its dianion, while the previously studied trianion B(C 3 O 2 ) 3 3À was thermodynamically unstable by À0.40 eV. [7] To validate our numerical method, we computed the structure and energetics of B(C 3 O 2 ) 3 3À using the same level of theory as used for the study of BeB 11 (CN) 12 3À (Supporting Information, Text 1).…”

Substituent‐Stabilized Organic Dianions in the Gas Phase and Their Potential Use as Electrolytes in Lithium‐Ion Batteries

“…The role of substituents in enhancing the stability of multiply charged species in the gas phase was recently studied by substituting H atoms in B 12 H 12 2− by CN moieties. The resulting B 12 (CN) 12 2− cluster was found to be unusually stable with the second electron bound by 5.3 eV, which is almost six times larger than that in the B 12 H 12 2− dianion . The power of substituent engineering was further demonstrated when a B atom in the cage was replaced by a C atom, to form CB 11 (CN) 12 2− .…”