- The N-lithiation of 2,4,6-triphenylborazine
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The reaction of the borazine Ph3B3N3H 3, 1, with a diethyl ether solution of LiMe/LiI/TMEDA yields [(Ph4B3N3H3)Li-(tmeda)LiI(tmeda)], 2. However, when halide free LiMe is used in the presence of TMTA, then (Ph 4B3N3H3)Li(tmta), 3, is formed which shows that a Me/Ph exchange occurs with the formation of LiPh which adds to 1 to form the borazinate 3. A Bu/Ph exchange is also observed in the reaction of 1 with LifBu/tmta. The product isolated from THF is compound [(Ph 4B3N3H2Li-Li(thf)3], 6c, which results from deprotonation of and LiPh addition to 1. A straightforward 1:1 LiPh addition reaction is observed on treatment of the borazine Ph 3B3N3Me3, 4, with LiPh in diethyl ether solution to give the borazinate (Ph4B3N 3Me3)Li(OEt2), 5. Reaction of 1 with LiPh (ratio 1:1) in diethylether produces (Ph4B3N 3H2Li)-[Ph3B3N3H 2Li(OEt2)2], 7, while an excess of LiPh leads to triple deprotonation and LiPh addition to the N atoms of compound (Ph 3B3N3Li3) to give the adduct [Ph3B3N3Li3(OEt2) 3]-[LiPh(OEt2)], 8. All new compounds have been characterized by spectroscopic methods and X-ray structure determinations. Wiley-VCH Verlag GmbH & Co. KGaA 2005.
- Noeth, Heinrich,Troll, Alexander
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- Structural chemistry of borazines
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The solid-state structure of (HN=BF)3 has been redetermined. It is characterised by a stacking of the molecules, similar to hexagonal boron nitride. In contrast, (F3CH2N=BF)3 shows no intermolecular interactions between the planar borazine rings. In (Cl 2BN=BCl)3, the Cl2B groups are almost perpendicularly oriented to the planar borazine ring and its B-Cl bonds are shorter than the Cl-B bonds to the ring boron atoms. Reactions of (Cl 2BN=BCl)3 with Me3SiNMe2 allows a successive Cl/Me2N exchange. Depending on the molar ratio, the compounds [Cl(Me2N)BN=BCl]3, [(Me2N) 2BN=BCl]3 and [(Me2N)2BN=BNMe 2]3 are obtained. The latter two react with CH 2Cl2 by B-N bond cleavage of one ring boron bonded Me 2N group with formation of an N-H bond. These molecules not only possess a strongly distorted BN hexagon with short B-NH bonds but also a nonplanar borazine ring. The nonplanarity of the borazine ring is even more pronounced in [Me3SiN=BCl]3. A planar borazine ring is observed for (MeN=BBr)3. Its molecules are ordered into stacks by translation with borazine planes 4.2 A apart from each other. Characteristic of the structure are close contacts between neighbouring bromine atoms. Due to the steric demand of pentafluorophenyl groups, the borazine ring of (F5C6N=BBr)3 forms no stacks because one of the three F5C6 rings stands almost perpendicular to the borazine plane while the other two are twisted by 70°. Aminolysis of (F 5C6N=BBr)3 yields (F5C 6N=BNH2)3 with NH2 groups that are coplanar with the borazine ring. The phenyl groups of (HN=BPh)3 are twisted by only 30-40° relative to the borazine ring. A threefold crystallographic axis stands perpendicular to the ring plane. The sixfold crystallographic axis of the unit cell generates a channel structure with an internal diameter of 4.5 A. The two isomeric borazines, (iPrN=BMe) 3 and (MeN=BiPr)3 are structurally rather similar although the first of these has longer B-N bonds due to the shorter N-C bonds. Moreover, the B-N-B and N-B-N bond angles are slightly different. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Anand, Benadir,Noeth, Heinrich,Schwenk-Kircher, Holger,Troll, Alexander
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p. 3186 - 3199
(2009/02/07)
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- Studies on 1-Trimethylsilyl-2,4,6-triethylborazine and Related Species
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Key Words: Boron-Nitrogen Compounds, Borazines, Unsymmetrically Substituted Borazines, Polyborazines The unsymmetrically substituted borazine (C6H5)3B3N3H2 has been obtained from the reaction of C6H5BCl2 with HN2, and an improved synthesis of (C2H5)3B3N3H2 has been developed.The reaction of the latter with an excess of BCl3 proceeds with the ultimate formation of Cl3B3N3H2, whereas the reaction with one molar equivalent of BBr3 leads to the formation of Br(C2H5)2B3N3H2a diborazinyl and additional products.C6H5BBr2 reacts with N3 to give the aminoborane 2NBBr(C6H5), but C6H5BCl2 does not undergo a reaction under analogous conditions.
- Niedenzu, Kurt,Serwatowska, Joanne,Serwatowski, Janusz
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p. 713 - 717
(2007/10/02)
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- REACTION OF DIBUTYL PHENYLBORATE WITH HEXAMETHYLDISILAZANE AND HEXAMETHYLCYCLOTRISILAZANE
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A study was carried out on the reaction of dibutyl phenylborate with hexamethyldisilazane and hexamethylcyclotrisilazane in the presence of a catalyst, which leads to B-triphenylborazine and various butoxysilazanes.The formation of a mixed B,N,O heterocyclic compound is also observed in the reaction with hexamethyldisilazane.
- Svatikov, M. Yu.,Gruzinova, E. A.,Kotrelev, G. V.
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p. 1494 - 1496
(2007/10/02)
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- Reactions of borazines with pyrazole and related studies: (μ-Amido)(μ-pyrazolato)diboron species, novel relatives of the pyrazaboles
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The reaction of borazines, (-BRNR′-)3, with pyrazole, Hpz, gives (μ-pyrazolato)(μ-amido)diboron species of the type R(pz)B-(μ-pz)(μ-NHR′)BR(pz) (3) containing a central B2N3 ring system. Four compounds of type 3 with R = C
- Bielawski,Das,Hanecker,Niedenzu,N?th
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p. 4623 - 4628
(2008/10/08)
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- Boron-nitrogen compounds. XII. Reaction of some silicon-nitrogen compounds with boron derivatives
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Reactions of aminosilanes with some boron compounds have been investigated. N-Silylated mono-, bis-, and trisaminoboranes were prepared by transamination. A study of the interaction of bis(trimethylsilyl)amine with (dimethylamino)-chlorophenylborane yielded a new type of bisborylamine.
- Jenne, Harry,Niedenzu, Kurt
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