The crystal and molecular structures of a series of N‐phenyl‐substituted lithium hydrazides were determined in order to investigate possible Li···Ph π interactions. These are pronounced when there are no donor molecules present to solvate the Li centers. An η6‐Li···Ph interaction is particularly distinct in tetrameric (Me3Si)2N–N(Ph)Li but also in trimeric Ph2N–N(SiMe3)Li Deprotonation of N,N′ ‐diphenylhydrazine with butyllithium in ether resulted in the formation of Ph(Li)N–N(Ph)Li · 2 LiNPh2 · 2 OEt2 with phenyl group migration and N–N bond cleavage by a redox process. An increase of the size of the cations, as shown for Ph(Me3‐Si)N–N(Ph)Na · NH3 and the caesium salt (Me3‐Si)2N–N(Ph)Cs · nTHF, results in increased coordination of the metal ion to the phenyl group. The caesium compound forms a three‐dimensional network. Channels along the c axis are partially filled with THF molecules.

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°.

Reaction of the N‐lithioborazine LiH2N3B3Me3·OEt2 (2) in diethyl ether with PCl3 or PBr3 leads to the borazinylphosphanes (Me3B3N3H2)PX2, (Me3B3N3H2)2PX (X = Cl, Br), and (Me3B3N3H2)3P, depending on the initial stoichiometry. The analogous arsane and stibane derivatives were obtained in a similar manner. While (Me3B3N3H2)2PBr is reduced byLiAlH4 in diethyl ether/hexane to give the monophosphane (Me3B3N3H2)2PH (13), the reaction of (Me3B3N3H2)PBr2 (5) with LiAlH4 in diethyl ether/hexane produces the zwitterionic compound [Me3B3N2(HN)]–P+H2Et (14). Dehalogenation of (Me3B3N3H2)2PBr (6) with Na yields the diphosphane (Me3B3N3H2)2PP(H2N3B3Me3)2 (18), while the mixed diphosphane (Me3B3N3H)2PPmes2 (17) is obtained from 6 and LiPmes2. Dehalogenation of Me3B3N3H2PBr2 with Na results in the exclusive formation of (Me3B3N3H2)4P4 (19), while the reaction of 5 with Li2Pmes leads to a mixture of cyclotetraphosphanes (mes)4–n(Me3B3N3H2)nP4 (A–F) along with bicyclic P4mes2. The new compounds have been characterized by NMR and IR spectroscopy and partly by mass spectrometry. X‐ray structures for compounds, 4, 5, 6, 9, 13, 14, 17, 18, 19, and E have been determined. All show different B–N bond lengths within the borazine rings, and some have borazine rings in a half‐chair conformation.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Borazines of type R 3 B 3 N 3 H 3 (R = Me, Et, i-Pr, t-Bu, Ph) add AlBr 3 and GaCl 3 in a 1:1 ratio to one of its N atoms. During this process the planarity of the borazine is lost. The ring system of the adducts show a semi chair conformation. HBr gas reacts with R 3 B 3 N 3 H 3 . AlBr 3 in toluene with formation of hitherto unknown borazinium tetrabromo aluminates (R 3 B 3 N 3 H 4 ) + (AlBr 4 ). The ring system of the cation is almost planar but it shows like the adducts three different B-N bond lengths.