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Borate ions occur, alone or with other anions, in many borate and borosilicate minerals such as borax, boracite, ulexite (boronatrocalcite) and colemanite. Borates also occur in seawater, where they make an important contribution to the absorption of low frequency sound in seawater. [1] Borates also occur in plants, including almost all fruits. [2]
An important synthetic application using such dialkylboranes, such as diethylborane, is the transmetallation of the organoboron compounds to form organozinc compounds. [9] [10] Some diaryl and dialkylboranes are well known. Dimesitylborane is a dimer (C 6 H 2 Me 3) 4 B 2 H 2). It reacts only slowly with simple terminal alkenes.
Trimethyl borate is a popular borate ester used in organic synthesis. Borate esters form spontaneously when treated with diols such as sugars and the reaction with mannitol forms the basis of a titrimetric analytical method for boric acid. Metaborate esters show considerable Lewis acidity and can initiate epoxide polymerization reactions. [4]
The Borate Minerals are minerals which contain a borate anion group. The borate (BO 3) units may be polymerised similar to the SiO 4 unit of the silicate mineral class. This results in B 2 O 5, B 3 O 6, B 2 O 4 anions as well as more complex structures which include hydroxide or halogen anions. [2] The [B(O,OH) 4] − anion exists as well.
Unlike silicates, boron minerals never contain boron with coordination number greater than four. A typical motif is exemplified by the tetraborate anions of the common mineral borax, shown at left. The formal negative charge of the tetrahedral borate center is balanced by metal cations in the minerals, such as the sodium (Na +) in borax. [1]
The ratio of tellurate to borate reflects the degree of condensation. In [TeO 4 (BO 3) 2] 8-the anions are linked into a chain. [1] In [TeO 2 (BO 3) 4] 10− the structure is zero dimensional with isolated anions. These arrangements of oxygen around boron and tellurium can have forms resembling silicates. The first borotellurates to be ...
Ulexite is a borate mineral because its formula (NaCaB 5 O 6 (OH) 6 ·5H 2 O) contains boron and oxygen. The isolated borate polyanion [B 5 O 6 (OH) 6] 3− has five boron atoms, therefore placing ulexite in the pentaborate group. Ulexite is a structurally complex mineral, with a basic structure containing chains of sodium, water and hydroxide ...
Lithium metaborate forms glass relatively easily, and consists of approximately 40% tetrahedral borate anions, and 60% trigonal planar boron. The ratio of tetrahedral to trigonal boron has been shown to be strongly temperature dependent in the liquid and supercooled liquid state. [3] [4]