Borazine and benzene

The magnetic fieid B points toward the viewer. The structures were optimized at the B3LYP/6-31G ievei of density function theory. The current density was caicuiated using the continuous set of gauge transformation (CSGT) method [54]. 

---

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... 

Borazine is isoelectronic with benzene, as B=N is with C=C, (Fig. 16.21). in physical properties, borazine is indeed a close analogue of benzene. The similarity of the physical properties of the alkyl-substituted derivatives of benzene and borazine is ever more remarkable. For example, the ratio of the absolute boiling points of the substituted borazines to those of similarly substituted benzene is constant. This similarity in physical properties led to a labeling of borazine as "inorganic benzene." This is a misnomer because tbe chemical properties of borazine and benzene are quite different Both compounds have aromatic rr clouds of electron density with potential for delocalization over all of the ring atoms. Due to the difference m electronegativity between boron and nitrogen, the cloud in borazine is "lumpy" because more electron... 

Table 1.7 shows quasi-particle calculations with a virtual space whose dimension has been reduced by the use of the QVOS procedure. As much as 50% of the virtual space s dimension was eliminated in these calculations, and errors of only 0.1 eV were introduced. With the larger, cc-pVQZ basis set, the errors that are introduced are smaller. In general, a larger basis set will result in a larger virtual space, and therefore, a larger reduction (in percentages) is possible. In P3 calculations on the larger molecules, benzene and borazine, similar errors were found [27],... 

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... 

The electronic difference between benzene and borazine is further supported by the properties of compounds of the type (R<,BjN j)Cr(CO)j. Although the.se are formally analogous to (rj< -QRf,)Cr(CO)j. the bonding is not nearly so strong in the borazine complex—its ring-metal dissociation energy appears to be about one-half that of the arene complex. In addition, there is considerable evidence that the borazine molecule is puckered in the.sc complexes. The actual structure appears to be intermediate between a true tt complex and the extreme rr-only model ... 

The similarity between benzene and borazine is superficial, and parallels are found only among the physical properties. 

Chapters chemistry ofthe Main Group Elements TABLE 8.6 Benzene and Borazine... 

Figure 14.2 ]t- lone pairs recovered by the AdNDP analysis for benzene and borazine. 

---