Studies on the cyclotetrazenoborane ring and related systems
Work done previously on cyclotetrazenoboranes and other boron-nitrogen ring systems, excluding borazines, has been comprehensively reviewed. The frequencies of the B-H stretching frequencies in and Ph IkBK have been studied in a range of solvents, and are shown to increase with increasing polarity of the solvent. No correlation is observed with the dielectric relationship and non-linear relative shift plots are obtained against, and transition metal hydride M-H vibrations. The results suggest that solvent interactions occur with parts of the molecules remote from the B-H bond, and are unlikely to be due mainly to dielectric effects. Two routes for the preparation of B-substituted cyclotetrazenoboranes have been developed. The action of Grignard reagents on derivatives of the type RN BH produces compounds in high yield, through the intermediate formation of magnesium containing complexes. Thermal degradation of a diorganoboron azide in the presence of an organic azide also produces boron-substituted cyclotetrazenoboranes. The preparation of B-halogeno substituted cyclotetrazenoboranes has been achieved by two routes. Direct reaction of a derivative of the type R2N4BH with N-bromosuccinimide has led to isolation of the very readily hydrolysable compound R2N4BBr. Dehydrohalogenation of a primary amine -BCl3 adduct in the presence of triethylamine has also led to the isolation of a B-chloro cyclotetrazenoborane derivative. Attempts to prepare unsymmetrically N-substituted cyclotetrazenoboranes by the reaction of a primary amine-borane (RNH2BH3) with an organic azide (R?N3) have led to the isolation of mixtures of cyclotetrazenoborane derivatives RRN4BH, RR?N4BH and R'R'N4BH. Throughout the work the U.V. I.R. and N.M.R. spectra of the compounds have been studied. A detailed mass-spectrometrie study of both B- and N-substituted cyclotetrazenoboranes has been made and a generalised fragmentation pattern has been derived. The use of computer techniques was also established to aid the handling and interpretation of the mass spectral data.