Borazole derivatives

B shifts of borazole derivatives, (RBNR )3 p.p.m. from Et20,Bp3 ... 

Most routes to boron nitride referred to in literature make use of borazole derivatives [4,73-80]. A large variety of different ligands, R and R, have already been mentioned. 

Borazole (borazine), derivatives of, from boron halide-amine coordination compounds, 5 28 Boric acid, H3BO3, esters of, 6 29 Boron bromide, 3 27, 29 Boron chloride, 3 27, 28, 29 Boron chloride-trimethylamine, 6 27... 

The stable borazole or triborine-triamine B3N3H6 is completely analogous to and isoelectronic with benzene with the same structure, stability, mesomerism and even the same smell. Also derivatives analogous to symm. trichlorobenzene and meta-dibromobenzene are known. 

Brown made a theoretical study of the electronic structure of rr-complexes of heteroaromatic systems, and predicted rr-complexes of borazoles to be less stable than the corresponding complexes of benzene (95). Although many attempts to synthesize a 7r-borazole complex were unsuccessful, Et3B3N3Me3 and Me3B3N3Et3 derivatives were later prepared from the hexacarbonyl by irradiation. [Cr(CO)3(MeftB3N3)] (LV) was eventually... 

These two compounds are among the thermally more stable boron halide-amine compounds. Compounds derived from certain primary and secondary amines lose hydrogen halides at elevated temperatures to give condensed boron-imide or borazole (borazine) derivatives. 

Semiyen and Phillips used an empirical method to calculate the retention times at 1,3,5,-trialkylborazoles. Retention parameters for individual alkyl groups were calculated from the log tR (logarithm of the individual retention times relative to mesitylene log tR = 2) values of the S3nnetrical 1,3,5,-derivatives by subtracting the log t of borazole (0.54) and dividing by 3. 

Table 30. Differences between Observed and Calculated log t values of some 1,3,5-Trialkyl Derivatives of Benzene and Borazole...

Semiyen and Phillips calculated the log tR values of methyl-and ethyl-borazoles, substituted on both boron and nitrogen atoms of the ring from retention parameters in the same way as the un-S3mimetrical trialkyl derivatives. Table 32 lists the numerical differences in the observed and calculated log tR values. 

Another series isoelectronic to benzene derivatives is that of borazines or borazoles in which each C-C couple is replaced by the isoelectronic B-N couple ... 

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