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Khodabocus, Monaf (1965) Thermolysis of certain organo-boron-nitrogen compounds. Masters thesis, Northern Polytechnic.
Alkylammonium trichlorophenylborates, RNH₃⁺(PhBCl₃)⁻, analogous to the tetrahaloborates already studied in these laboratories, were prepared and their properties studied. Dry pyrolysis of these salts led to B-trichloroborazines by elimination of 1 mol of benzene and 2 mol of hydrogen chloride in the sterically unhindered systems. The results were compared with the pyrolysis of analogous tetraphenylborates, which led mainly to the aminodiphenylboranes. The results of bench pyrolysis were confirmed in the main by differential thermal analysis. Agreement with thermogravimetric analysis was less close.
Decomposition of the trichlorophenylborates in boiling solvents was by preferential dehydrochlorination with little dehydrophenylation, leading, in the case of unhindered systems to the B-phenylborazine. The s-butyl system dehydrochlorinated to s-butylaminochlorophenylborane which dimerised slowly on standing. An attempt at the quantitative estimation of the energy of the ժ-coordinate N → B bond of the solid dimer by D.T.A. showed it to be of the order of H-bonding.
Dehydrochlorination of the trichlorophenylborates with triethylamine led to the B-phenylborazine in the case of the n-propyl system, and the aminochlorophenylboranes, RNHB(Ph)Cl, in the Buˢ and Buᵗ systems. The i-butylammonium trichlorophenylborate or its corresponding (1:1) complex, on dehydrochlorination with triethylamine in petroleum (b.p. 30–40°), yielded the tetrameric and trimeric B-phenylborazines. The tetramer (PhBNBuⁱ)₄ was found to revert quantitatively and irreversibly to the trimer, (PhBNBuⁱ)₃. This result was confirmed by D.T.A.
Attention is drawn to the anomalous values obtained for the molecular weights of some B-phenyl BN cyclic compounds, including hexaphenylborazine (Chapter I) - as determined ebullioscopically in certain organic solvents. Results from three different colligative methods and from mass spectrometry are discussed (Chapter VI).
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