The results of a theoretical study on the formation of the nitrogen cluster N-10 from the ionic species N-5(+) and N-5(-) are presented. The possibility to form N-8 from N-5(+) and N-3(-) has also been studied but no stable form was found. Structural and vibrational data are given for the different clusters. It is suggested that the anion N-5(-) might be stable enough to be synthesized. The calculations have been carried out using multiconfigurational self-consistent-field wave functions and second-order perturbation theory.