We present a first-principles theoretical study of complexes formed by combination of C rings and group-V atoms, which are the passivated analogs of the C28 fullerene. We study structural and electronic properties of C24X4 clusters, with XN, P, As, in comparison to C28 and C28H4. All clusters with group-V atoms are predicted to be stable and chemically passive, with large HOMO-LUMO gaps. The conditions under which these clusters may be formed experimentally are considered. We also study the (BN)12N4 cluster, in isoelectronic equivalent of C28N4, and find a particularly stable and chemically passive isomer.