On the bonding nature of the N5+(=N(N2)2+) cation and related species N(CO)x+, N(NH3)x+, and NRx+, x = 1, 2 and R = He, Ne, Ar, Kr.: Do we really need the resonance concept?

We attempt to elucidate the bonding nature of the isoelectronic and isovalent cations N-5(+)(=N(N-2)(2)(+)) and N(CO)(2)(+), the salts of which have been recently isolated. By performing coupled-cluster RCCSD(T) calculations, we argue against the "resonance" bonding approach as redundant, and we claim that the bonding in the aforementioned species is naturally explained by realizing that the in situ central nitrogen (N+) finds itself in the first excited D-1 state, thus forming two equivalent dative bonds with N-2 and CO, respectively. To further support our position, we have also studied at the same level of theory the molecules NNH3+, N(NH3)(2)(+), NR+, and NR2+, where R = He, Ne, Ar, and Kr. It is predicted that the N(NH3)(2)(+) system is clearly isolable, whereas under certain conditions, NKr2+ (and perhaps NXe2+) could also be "trapped" experimentally.