The N-lithioborazine LiH2N3B3Me3, 1, reacts with organoboron halides not only to the respective borazinyl organylboranes but also by Me/halogen exchange. (Me2N)2B-H2N3B3Me3 was obtained from 1 and (Me2N)2BCl. A new ten-membered B6N4 ring system, 5, results on treatment of Cl(Me2N)B-B(NMe2)Cl with 1. The B-N-borazinyl borazines 6 - 8 can be prepared from 1 and B-monohalo borazines. The synthesis of 2,4,6-trimethylborazinyl-aluminum and -titanium compounds is achieved only with mononuclear monohalides of Al(III) and Ti(IV). The 2,4,6-trimethylborazinyl- bis(piperidino)alane 9 and the tris(2,6-diisopropylphenoxo)-2,4,6-trimethylborazinyltitanium 10 were characterized by X-ray structure analysis.
The distortion of the borazine ring by B and N substitution is discussed. In case of the N-substituted borazines YH2N3B3Me3 the B-N bonds of the YNB2 units are elongated, e. g. for Y = PBr2 or (RO)3Ti, while N lithiation leads to a shortening of these B-N bond. These changes of bond lengths are also reflected by changes in the B1-N2 and B3-N3 bond lengths which become shorter in the presence of electron-withdrawing groups, but longer in case of Li substitution. Also, the bond angles B1-N2-B2 and B2-N3-B3 are affected by an increase of up to 128°.
通过B和N取代引起的硼氮杂环畸变进行了讨论。对于N取代的硼氮杂环YH2N3B3Me3,YNB2单元的B-N键被延长,例如对于Y = PBr2或(RO)3Ti,而N锂化导致这些B-N键的缩短。这些键长的变化也反映在B1-N2和B3-N3键长的变化上,在电子吸引基团存在时变短,但在锂取代的情况下变长。此外,键角B1-N2-B2和B2-N3-B3受到影响,最多增加128°。