title: Carborane acids. New "strong yet gentle" acids for organic and inorganic chemistry.
abstract: Icosahedral carborane anions such as CHB11Cl11- are amongst the least coordinating, most chemically inert anions known. They are also amongst the least basic, so their conjugate acids, H(carborane), are superacids (i.e. stronger than 100% H2SO4). Acidity scale measurements indicate that H(CHB11Cl11) is the strongest pure Brønsted acid presently known, surpassing triflic and fluorosulfuric acid. Nevertheless, it is also an extremely gentle acid--because its conjugate base engages in so little chemistry. Carborane acids separate protic acidity from anion nucleophilicity and destructive oxidative capacity in the conjugate base, to a degree not previously achieved. As a result, many long-sought, highly acidic, reactive cations such as protonated benzene (C6H7+), protonated C60(HC60+), tertiary carbocations (R3C+), vinyl cations (R2C=C(+)-R), silylium ions (R3Si+) and discrete hydronium ions (H3O+, H5O2+ etc.) can be readily isolated as carborane salts and characterized at room temperature by X-ray crystallography.
authors.affiliation: Department of Chemistry and Center for S and P Block Chemistry, University of California, Riverside, California 92521-0403, USA. chris.reed@ucr.edu
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Reed
mesh_terms: D000143:Acids / Q000737:chemistry*; D000473:Alkanes / Q000737:chemistry; D000478:Alkylation; D000838:Anions / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry*; D015392:Chemistry, Inorganic / Q000379:methods*; D002625:Chemistry, Organic / Q000379:methods*; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009861:Onium Compounds / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D011522:Protons
chemical_list: D000143:Acids; D000473:Alkanes; D000838:Anions; D002254:Carbonates; D007477:Ions; D009861:Onium Compounds; D010087:Oxides; D011522:Protons; C027727:hydronium ion