The results of Hartree-Fock (with relativistic effective core potentials) followed by variational and second order multireference perturbational configuration interaction (CIPSI) calculations are reported for the linear (C-xv) and bent (C-2v) electronic states of the RuN2 molecule which arise from the ground state Ru(F-5;d(7)s(1)) + N-2 and the first excited state Ru(F-5;d(7)s(1)) + N-2 of the free fragments. For both coordination modes, the most important metal-ligand interaction channels are obtained for those states correlating with the low-multiplicity asymptotic limit. Due to the existence of symmetry-avoided crossings involving the potential energy curves which evolve from the second-lying triplet state of the separated fragments, Ru(F-5;d(8)) + N-2 the ability of ruthenium to capture the N-2 molecule through these low-multiplicity channels is strongly determined by the maximal d-shell occupancy metallic state. (C) 2003 Elsevier B.V. All rights reserved.