n ‐Butyldichloroborane

Synthesis and Reactions of Borazines

“…The boron precursors employed for these syntheses can include: tris(dimethylamino)borane­, triisopropoxyborane, triethoxyborane, tris(propyl­thio)borane, boric acid, borane–dimethyl sulfide, boron trichloride, and boron tribromide. 6 12 , 120 121 122 The aromatic amines that serve as efficient precursors include aniline substituted at the ortho -position with amino, hydroxy, or mercapto groups. 6 12 , 120 121 122 Besides aromatic amines, 1,2- or 1,3-substituted bifunctional aliphatic amines such as aliphatic diamines, aliphatic N -monoalkylated amine, diamines, aliphatic amino alcohols, and aliphatic amino thiols also afford the corresponding polycyclic borazines under similar conditions.…”

“…As noted in the introduction, the first confirmed synthesis of borazine ( 1 ) was reported in 1926 by Stock and Pohland. 3 6 This pioneering synthesis involved reaction between ammonia and borane to form an adduct, presumably borane–ammonia complex ( 2 ), and subsequent pyrolysis of this adduct at 200 °C in a bomb tube (Scheme 1 ). One atmosphere of pressure during the course of the reaction was found to lead to borazine in 45% isolated yield.…”

“…6 12 , 120 121 122 The aromatic amines that serve as efficient precursors include aniline substituted at the ortho -position with amino, hydroxy, or mercapto groups. 6 12 , 120 121 122 Besides aromatic amines, 1,2- or 1,3-substituted bifunctional aliphatic amines such as aliphatic diamines, aliphatic N -monoalkylated amine, diamines, aliphatic amino alcohols, and aliphatic amino thiols also afford the corresponding polycyclic borazines under similar conditions. 6 12 , 120 121 122 Boiling xylene, benzene, or chlorobenzene are the most common useful solvents applied to perform these transformations.…”

“…Structurally, the B–N bond length in borazine is ~1.44 Å is intermediate between the length of a B–N single bond (1.54 Å) and the length of a B–N double bond (1.36 Å). 6 7 However, the B–N bond length may vary according to substitution pattern of a given derivative. In the parent system the B–H bond length is 1.20 Å and N–H bond length is 1.02 Å.…”

“…Further, the N–B–N bond angle in borazine is ~117°, whereas its B–N–B bond angle is ~122°. 6,7 The B–N bond length of borazine is a manifestation of dative bonding between the electron lone pairs in the filled p-orbital of nitrogen with the empty p-orbital on boron, giving rise to the borazine cyclic π-electron cloud. However, due to the significant difference in the electronegativity of boron and nitrogen atoms, more π-electrons are concentrated in the vicinity of nitrogen atoms of the borazine ring than at the boron center.…”