Polyhedral molecules of boron nitrides

MNDO calculations with geometry optimization for two isomeric polyhedral boron nitride molecules B12N12 (1 and 2) are reported. Structure 1 with the truncated octahedral form is more stable than the form 2 with symmetry group C60. Optimized structures of the two isomers, 3 and 4, of molecules X6Y6(CH2)6 (X=N, Y=B) which model the fragments of structure 2 are also calculated. The possibility of stabilization of the cyclic N6 cluster by polyhedral structures is discussed. Finally, the results of calculations of the polyhedral boron nitride molecules are compared with those obtained for their carbon analogs