Boron-nitrogen analogues of carbon compounds

Boron-nitrogen analogues of carbon compounds The simplest compounds of this kind are molecules 

Cyclic molecules with alternate B and N atoms include aromatic 4-, 6-, and 8-membered rings and saturated molecules with 4- and 6-membered rings. In the former B—N is close to 1-42 A and in the latter, 1-60 A. Examples are given in Fig. 24.10. In the molecule, (a) the 4-ring is planar and the three bonds from each N are coplanar, but the shortness of the exocyclic B-N bond (1-44 A, the same as in the ring) is not consistent with the fact that the planes NSi2 are approximately 

Cyclic boron-nitiogen, boron-phosphorus, and boron-carbon molecules. 

The ethylene-like molecules R2N. BX2 readily polymerize, and the dimers and trimers are the analogues of substituted cyclobutanes and cyclohexanes. Molecules of type (d) have planar 4-membered rings with B-N close to 1-60 A, and the molecule (e) has the chair configuration. The phosphorus analogue of (e) has been shown to have a similar configuration with B-P, T94 and 

Miscellaneous cyclic boron compounds include (g), with a 5-membered N4B ring,( and (h), with a B3C3 ring and double bonds to the N(CH3)2 groups.  

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