34989-01-0Relevant academic research and scientific papers
Thermal dehydrochlorination in the 4-fluoroaniline-trichloroborane system: identification of reactive intermediates involved in the formation of B,B′,B′′-trichloro-N,N′,N′′-tri((4-fluoro)phenyl)borazine
Hahn, Jennifer,Krieg, Matthias,Keck, Constanze,Maichle-M?ssmer, C?cilia,Fink, Reinhold F.,Bettinger, Holger F.
, p. 17304 - 17316 (2018)
Borazines are used in chemical vapor deposition processes to produce hybrid graphene-boron nitride nanostructures. As the knowledge on the mechanism of borazine formation is scarce, we studied the mechanism of formation of B,B′,B′′-trichloro-N,N′,N′′-tri(p-fluorophenyl)borazine (3a) from p-fluoroaniline and boron trichloride employing NMR spectroscopy, X-ray single crystal structure analysis, trapping experiments, and computational chemistry methods up to the coupled cluster CCSD(T) level of theory. These studies suggest the initial formation of the 1?:?1 adduct 1a (ArNH2BCl3, Ar = 4-fluorophenyl) with a dative B-N bond that could be fully characterized including single crystal X-ray diffraction. Adduct 1a undergoes unimolecular hydrogen chloride elimination with a first-order rate constant of k1 = 3.03(7) × 10?2 min?1 in toluene at 100 °C. This rate constant is in very good agreement with the one derived (k1 = 3.18 × 10?2 min?1) from computed activation parameters (ΔH?373.15 = 28.1 kcal mol?1, ΔS?373.15 = 1.56 eu, ΔG?373.15 = 27.6 kcal mol?1). The product of the first hydrogen chloride evolution is anilinodichloroborane ArNHBCl2 (2a). Compound 2a cannot be isolated in a pure form due to instability, but its presence as a transient reactive intermediate can be derived from NMR spectroscopy. Reactive intermediates other than anilinodichloroborane cannot be assigned by NMR spectroscopy. We propose that the mechanism of formation of borazine 3a involves the reaction of 2a with 4-fluoroaniline as the rate determining step.
1H and 13C NMR studies of η6-benzo-bonded (boron-nitrogen heteroarene)tricarbonylchromium complexes and related η6-phenyl-bonded (B, B', B''-trimethyl-N, N', N''-triarylborazine)-tricarbonylchromium complexes: crystallographic structure of a boron-nitrogen heteroarene
Allaoud, Smaiel,Conte, Seny,Fenet, Bernard,Frange, Bernard,Robert, Francis,et al.
, p. 59 - 68 (2007/10/02)
2,4-dimethyl-3-phenyl--7-chloro-8-methyl-2,4-dibora-1,3-diazaronaphthalene (C16H18B2N2Cl2) crystallizes in the monoclinic system: P2/a; a=8.149(3) Angstroem, b=13.379(3) Angstroem and c=15.193(3) Angstroem; β=91.03(2)o; Z=4; R=0.043; Rw=0.041.Reaction with gives exclusively the compounds with Cr(CO)3 η6-bonded to the benzo part of the molecule.This derivative is a 1:1 mixture of atropisomers which were partially separated and whose configurations could be deduced by means of solvent effects in nuclear magnetic resonance (NMR) spectroscopy.Similar results were obtained with 2,4-dimethyl-3-phenyl--6-chloro-8-methyl-2,4-dibora-1,3-diazaronaphthalene and although the separation of isomers failed.Additionally, two closely related η6-bonded isomers originating from the above ligands were identified in which the chlorine atom was replaced by a hydrogen atom.All these compounds were thoroughly characterized by high resolution 1H and 13C one-dimensional and 1H-1H nuclear Overhauser spectroscopy (NOESY) and correlated two-dimensional NMR spectroscopy (COSY).Further, the reaction of with B,B',B''-trimethyl-N,N',N''-triarylborazine, the phenyl bearing a para substituent (H, F or Me), was shown by 1H and 13C NMR spectroscopy to yield a compound with one phenyl group η6 bonded to Cr(CO)3.Key words: Chromium; Boron; Nuclear magnetic resonance
