Semiempirical AM1 and B3LYP/6-31G* density functional theory methods have been used to examine the relative stabilities of various isomers of C₅₉XHCl_2n, C₆₀H₂Cl_2n and C₅₉XH₅, where X＝N, B and n＝1～2. The calculation results indicate that the energetically favored isomers of C₅₉XHCl_2n, C₆₀H₂Cl_2n and C₅₉XH₅ are those isomers in which the first and/or the second H₂ or Cl₂ reactants are all attached to the carbons in the vicinity of the functionalized part of the cage. The difference in regioselectivities between C₅₉NH and C₅₉BH can be attributed to the difference in electronic nature between N and B atoms. And the difference in steric effect between H and Cl atoms may be the primary factor that results in the different addition patterns of hydrogenation and chlorination of C₅₉NH and C₅₉BH.

Key words: C₅₉NH, C₅₉BH, radical addition, relative stability, regioselectivity