Borazine analogous

Borazine is a colourless liquid (mp 215 K, bp 328 K) with an aromatic odour and physical properties that resemble those of benzene. The B N distances in the planar B3N3 ring are equal (144 pm) and close to those in the layered form of BN (Table 13.2). This is consistent with a degree of delocalization of the N lone pairs arotmd the ring as represented in 13.28. Structure 13.27 gives one resonance form of borazine, analogous to a Kekule structure for benzene. Despite the... 

Borazine, (HBNH)3, analogous to benzene prepared by A. Stock and E. Pohland. 

C21-0046. Borazine (B3 N3 Hg ) is a planar molecule analogous to benzene (Cg Hg ). Write the Lewis structure and describe the bonding of borazine. 

The synthesis of borazine (Fig. 1) was first described in 1926 by Stock and Pohland.12 More recently, Wideman and Sneddon reported interesting three one-step synthetic procedures using various starting compounds including 2,4,6-trichloroborazine, metal borohydrides, and ammonia-borane.13 The B N bond is isoelectronic with the C C bond, which explains why borazine is often presented as the inorganic analog of benzene, that is, borazine has almost the same colligative properties as benzene. 

By analogy with B-trialkylaminoborazi ne and polyborazine derived therefrom, the first route envisioned to poly(borylaminoborazine) was the thermal condensation of molecular precursors under a convenient atmosphere. As detailed earlier the innovative idea behind this procedure is to tailor the polymeric precursor structure by increasing the distance between the two borazinic rings. For that purpose, we explored... 

The original method1 reported for the preparation of trichloroborazine involves the use of borazine. However, this procedure is not recommended because of the difficulty of preparing this heterocycle and its hydrolytic instability. More recently, this trichloroborazine has been prepared directly from ammonium chloride and boron trichloride at elevated temperatures with or without a solvent.2-8 Ammonium chloride may be replaced by a primary aliphatic or aromatic amine or its hydrochloride, and organodihaloboranes can be used in place of the boron trichloride to give the respective N- and B-substituted borazines.6 Boron tribromide has been used in analogous reactions to yield -B,/ , .B"-tribromoborazines.6... 

The gas-phase chemistry of borazine B3N3H6 (147) and the conjugate N-protonated acid B3N3H7+ indicates analogies with benzene,189 although the aromatic stabilization energy of neutral borazine is only 30% that of benzene, and the reactivities of benzene and borazine are not similar (Scheme 62). Comparable conclusions were reached when HOMA and Iq aromaticity indices were used.190a... 

By analogy with borazines, the initial interest in the analogous unsaturated boron-phosphorus rings focused on the fundamental issue of the extent of... 

The procedure18 described below gives lightly cross-linked, pure poly(B-vinyl-borazine) (an inorganic analog of polystyrene) in good yields. 

IF the product were a monomer, its structure could be drawn as Cl2PsN, which is analogous to organic nitriles. R—C=N. For this reason the original names used for these compounds were phosphonitriles, phosphonitrilic chloride, etc. However, the products are actually either cyclic or linear polymers of general formula [NPC ,] . Thus, by analogy with benzene, borazine. etc., these compounds hove become known as phosphazenes. The rn jor product of the reaction in Eq. 16.47 and the easiest to... 

Spin-coupled calculations, analogous to those for the organic heterocycles, have been carried out for both molecules. Three of the spin-coupled n orbitals for borazine are related to each other by successive C3 rotations and they take the form of fairly localized, slightly distorted N(2p) functions. The other three orbitals are also transformed into one another by successive C3 operations. These are also based on N(2p) functions but clearly show significant delocalization onto neighboring boron centres. Nonetheless, most of the electron density remains on N. 

As the BN unit is isoelectronic with a C2 fragment, replacement of the latter by the former in various organic compounds leads to azaborane structural analogs. Some examples are shown below. Planar borazine (or borazole) B3N3H6 is stabilized by n -delocalization, but it is much more reactive than benzene in view of the partial positive and negative charges on the N and B atoms, respectively. 

The dccironic differeiKe between benzene and borazine is funher supported by the properties of compounds of the type (R,8iN])CrtCO)]. Although these are for-rrudly analogous to the bonding is not nearly so strong in the... 

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