Boron: Inorganic Chemistry

AbstractBoron is unique among the elements and displays remarkable chemistry in all of its compounds. It is widely distributed at low concentrations on the Earth and is virtually always found bound to oxygen in its natural forms. Boron enters into the life cycle of and is an essential element for plants and animals. The vast majority of industrial uses of boron on a weight basis also involve boron–oxygen compounds, including important mineral sources, metal borates, boric acid, boric oxide, and boric acid esters. These find large‐scale applications in many industries, most notably in the manufacture of glass and other vitreous materials. Boric acid is a weak Lewis acid and does not display Brønsted acidity in aqueous solution. The condensation of B(OH)3and B(OH)4−species to form polyborates in relatively concentrated borate solutions has important implications for the solubilities and other solution properties of metal and nonmetal borate salts. Boric acid reacts with alcohols and other hydroxyl group‐bearing compounds to form esters, which find many industrial uses. Reversible borate ester crosslinking leads to polymer gel formation and provides the basis for the essential biological role of boron. Nonoxide boron compounds also have important industrial uses. These include refractory compounds, such as boron carbide, boron nitrides, boron phosphides, elemental boron, and metal–boron alloys, as well as nonrefractories, such as the boron halides. Nonrefractory boron–phosphorus and boron–sulfur compounds and the boron subhalides are yet to find significant industrial use, yet, nonetheless exhibit fascinating chemistries.