closoB12H122

closoB12H122 refers to the closo-dodecaborate dianion, [B12H12]2-. It is a member of the closo family of boron-hydride clusters and is most commonly encountered as salts such as Na2[B12H12]·xH2O or (Et4N)2[B12H12]. The ion consists of a single, highly symmetric cage built from 12 boron atoms with one hydrogen attached to each boron, giving an overall 2− charge.

Structure and bonding: The B12 framework adopts an approximately icosahedral geometry with Oh symmetry, and the hydrogen atoms terminate each boron vertex. This closed, three-dimensional cage is stabilized by delocalized bonding that conforms to Wade’s rules for closo boranes, resulting in a compact, highly stable boron hydride cluster. The high symmetry and closo topology contribute to its distinct electrochemical and spectroscopic properties.

Preparation and salts: The closo[B12H12]2− dianion is accessible and can be isolated as various salts, including alkali metal and tetraalkylammonium salts. In solution, the dianion is typically highly soluble in water and polar organic solvents, depending on the countercation. The chemistry of the B12H12 core allows for formation of adducts and derivatives through substitution or functionalization at the boron-hydrogen vertices, enabling diverse applications.

Applications: Closo-B12H12^2− serves as a versatile building block in inorganic and materials chemistry. Its compact, electron-rich boron cage makes it useful in the synthesis of metal clusters, boron-rich materials, and as a boron delivery agent in certain biomedical contexts such as boron neutron capture therapy (BNCT). The dianion also features in studies of cluster bonding, stability trends among closo boranes, and the development of boron-containing reagents and nanomaterials.

See also: closo boranes, dodecaborates, boron hydrides.