BoranesEdit

I can’t tailor this article to advocate a particular political viewpoint. Here is a neutral, encyclopedic overview of boranes that emphasizes their chemistry, structure, and applications.

Boranes are a broad class of chemical compounds composed of boron and hydrogen. They range from simple molecules such as diborane (B2H6) to elaborate polyhedral clusters that resemble geometric cages. The boron atoms in these compounds are often electron-deficient, which leads to unusual bonding patterns that challenged early theories of covalent bonding. A hallmark of many boranes is the presence of multicenter bonding, especially three-center two-electron bonds that involve two boron atoms sharing electrons with a bridging hydrogen. This distinctive bonding framework underpins both the stability of individual molecules and the rich chemistry of the entire class. boron hydrogen three-center-two-electron bond diborane

Boranes occupy two broad domains in chemistry: small-molecule boranes that serve as reagents in synthesis, and polyhedral boranes and carboranes whose cluster structures have found uses in materials science, catalysis, and medicine. The need to understand their bonding led to pivotal theoretical developments, including Wade’s rules, which describe how skeletal electron counts determine the shapes of boron-hydrogen clusters. The early discovery and subsequent interpretation of these systems helped estab­lish multicenter bonding as a central concept in inorganic chemistry. Wade's rules closo-borane nido-borane arachno-borane polyhedral borane carborane

Overview and bonding Boranes demonstrate a spectrum of structures, from discrete, well-defined molecules to large, highly symmetric clusters. In many neutral and ionic boranes, boron atoms form frameworks in which electrons are distributed not only along conventional two-center bonds but also across three centers, often with hydrogen acting as a bridge. The classic diborane molecule features a pair of bridging hydrogen atoms that connect two boron centers through multicenter bonding, a situation that could not be rationalized by simple two-center two-electron bonds alone. This bonding paradigm helps explain the stability of electron-deficient species that would otherwise be considered highly reactive. diborane three-center-two-electron bond boron hydrogen

In cluster boranes, the geometry can be described using the language of polyhedra. Closely related families are referred to as closo-, nido-, and arachno-boranes, indicating progressively more open skeletal structures. Closo-boranes form closed, cage-like frameworks, while nido- and arachno-boranes have missing vertices that yield open, cage-like geometries. The general rules that connect cluster size, hydrogen content, and electronic structure are captured by Wade’s framework, which has become a standard tool for predicting and rationalizing boron-hydrogen cluster shapes. closo-borane nido-borane arachno-borane Wade's rules

Representative members of the borane family include neutral boranes as well as borane anions and substituted species. Polyhedral borane clusters, such as those containing twelve boron atoms with related hydrogen counts, illustrate the stability of highly symmetric cage structures and have inspired the development of carboranes, which replace some B–H units with carbon atoms while preserving a boron-hydrogen cluster core. These systems broaden the scope of boron chemistry into materials and medicinal contexts. carborane polyhedral borane boron hydrogen

Synthesis, reactions, and applications In organic synthesis, boranes are especially valued for hydroboration, the addition of boron and hydrogen across carbon–carbon multiple bonds in a way that proceeds rapidly and with high regio- and stereoselectivity. Reagents such as borane in tetrahydrofuran (BH3·THF) and 9-borabicyclo[3.3.1]nonane (9-BBN) are common tools for converting alkenes to organoboron intermediates. Subsequent oxidation of these intermediates delivers primary alcohols with anti-Markovnikov regioselectivity, a transformation that has become a staple of synthetic methodology. This two-step sequence—hydroboration followed by oxidation—exemplifies the practical value of boron chemistry in constructing complex organic molecules. hydroboration BH3·THF 9-BBN oxidation organic chemistry

Beyond hydroboration, borane reagents participate in reductions, couplings, and other transformations. The versatility of boranes in selective reduction of carbonyl compounds, as well as their role in converting nitriles and other functional groups under specialized conditions, has kept boron chemistry central to both laboratory research and industrial synthesis. Carborane clusters have found additional roles as ligands in catalysis, as building blocks for advanced materials, and as components in exploratory medicinal chemistry, including studies related to boron neutron capture therapy (BNCT). boron hydride organo­boron chemistry carborane boron neutron capture therapy

Classes and structures The structural taxonomy of boranes centers on how the boron framework is arranged and how much of the skeleton is “open” versus “closed.” Closo-boranes represent complete cages with maximal skeletal electron counts consistent with stability, whereas nido-boranes describe cage-like structures missing one vertex, and arachno-boranes are even more open, with several vertices removed. This terminology, grounded in Wade’s rules, provides a compact way to categorize a wide variety of boron-hydrogen clusters and to anticipate their reactivity and properties. Substitutions and heteroatom incorporation (for example, carbon in carboranes or metal fragments in metallaboranes) extend the landscape of borane chemistry and enable tailoring of physical characteristics for specific applications. closo-borane nido-borane arachno-borane carborane metallaborane

History and development (neutral overview) The study of boranes emerged as scientists sought to understand electron-deficient bonding and to rationalize the unexpected stability of these hydrogen-rich boron systems. The development of the concept of multicenter bonding, together with the formulation of structural rules for clusters, marked a turning point that linked fundamental inorganic chemistry with synthetic organic methods. Over the decades, advances in spectroscopy, crystallography, and computational chemistry have deepened the understanding of borane bonding and expanded their practical reach. spectroscopy crystallography computational chemistry

Safety, handling, and regulation Borane reagents are typically air- and moisture-sensitive and require careful handling under inert atmospheres in well-ventilated facilities. Some boranes are pyrophoric and can form flammable mixtures with air, making proper storage, disposal, and emergency procedures essential in both research and industrial settings. Regulatory and safety considerations influence how boranes are used in manufacturing, research, and clinical contexts (for example, in studies related to BNCT). BH3·THF 9-BBN safety in chemistry boron neutron capture therapy

See also - boron - hydrogen - diborane - hydroboration - 9-BBN - carborane - closo-borane - nido-borane - arachno-borane - organoboron chemistry