Borazine

DescriptionBorazole (borazine) is a colourless liquid with an aromatic smell. With water, it decomposes to form boric acid, ammonia, and hydrogen. The reaction product of boron and ammonia at high temperatures is also known as inorganic benzene.

UsesBorazine can be useful in the study of structural stability and the low-lying singlet and triplet states of BN - n -acenes, n = 1-7.

General DescriptionBorazine can be prepared by copyrolysis of NaBH4 and NH4Cl in a highboiling glyme, by reduction of trichloroborazine, or by pyrolysis of ammonia borane in diglyme.A large body of literature exists on the preparation and chemistry of symmetrically and unsymmetrically substituted borazines. B-Substituted trihaloborazines, readily prepared from BX3 and NH4Cl, react with Grignard reagents to give symmetrical trialkyl- or triarylborazines. Symmetrically substituted N-trialkylor N-triarylborazines are readily prepared from LiBH4 and RNH3Cl, or by pyrolysis of RNH2BH3.Borazine is thermally stable at 0 C, but decomposes slowly at ambient temperature. Borazine hydrolyzes slowly, but trihaloborazines hydrolyze quite rapidly. Hydrogen halides form 1 : 3 adducts with borazine, which decompose to trihaloborazines on warming.

PreparationBorazine was discovered when a mixture consisting of B3H6 and NH3 (or the addition product B3H6-NH3) was heated in a sealed tube. It can also be produced by pyrolysis of a mixture of LiBH4 and NH4Cl. The best yield is obtained by reducing (ClBNH)3 with LiBH4 in n-butyl ether. This reaction also yields B2H6.