Ab initio calculations at the B3LYP and MP2 levels suggest that a series of compounds with the general formula N5MN7 (M = Ti, Zr, Hf, Th) are locally stable. These compounds are thermodynamically at least as stable as the recently suggested ScN7 molecule. N5ThN7 seems the most stable of all. It lies 21.5 kcal/mol below a transition state, corresponding to the opening of one N-N bond in the N-7 ring, and only 132 kcal/mol above Th + 6 N-2, or 22 kcal/(mol N-2).