Hydrido complexes

Article By:

Warf, James C. Department of Chemistry, University of Southern California. Los Angeles, California.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.327600

Complex hydrides containing a hydride ligand bonded to a central atom. The prefix hydro instead of hydrido is sometimes used. Sodium tetrahydridoborate, NaBH₄ (or sodium tetrahydroborate, originally called sodium borohydride), and lithium tetrahydridoaluminate, LiAlH₄ (originally called lithium aluminum hydride), are important reducing agents in synthetic and industrial reactions. NaBH₄ is employed in aqueous or alcoholic solutions, and LiAlH₄ is employed in ethers. Sodium cyanotrihydridoborate, NaBH₃CN, can be used in acidic medium. A family of aluminum-based reducing agents is now available commercially, including sodium diethyldihydridoaluminate, NaAlH₂(C₂H₅)₂; sodium tri-tert-butoxohydridoaluminate, NaAlH(O-t-C₄H₉)₃; and sodium bis(2-methoxyethoxo)-dihydridoaluminate, NaAlH₂(OCH₂CH₂OCH₃)₂. All are soluble in aromatic hydrocarbons. They are rather expensive, but their specific reducing powers make them attractive for synthesizing high-value products, such as pharmaceuticals, flavorings, fragrances, dyes, and insecticides.

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