A kinetic stability study of MN5 (M = Li, Na, K, and Rb)

A structure and kinetic stability study on some complexes with the general formula MN5, where M are the alkali-metal atoms, Li, Na, K, and Rb, has been carried by using hybrid density functional methods. Complex B (C-2nu) with two points of attachment to the N-5 ring is the most energetically favored for all metals considered here. Pyramidal structures A (C-5nu) are kinetically unstable and they rapidly rearrange to the most stable planar structures B. At the QCISD(T)/6-311 + G*//B3LYP/6-311 + G* + ZPE (B3LYP/6-311 + G*) level, the decomposition barrier heights of LiN5-B, NaN5-B, KN5-B, and RbN5-B are predicted to be 19.9, 22.0, 22.5, and 23.0 kcal/mol, respectively. In addition, the rate constants of the decomposition reaction MN5-B --> MN3 + N-2 (M = Li, Na, K, and Rb) are also predicted using conventional transition state theory and canonical variational transition state theory, respectively.