Structures of nitrogen-rich sulfides SN5 and SN6 (neutral molecules and ions) with low spin are optimized and characterized by harmonic vibrational frequency analysis using ab initio and density functional theory methods. Their stability is studied by evaluating dissociation barriers and by comparison of their total energies with those of (1)/S-8(8) + (x)/N-2(2) (x = 5, 6). The important role d orbitals play in nitrogen-rich sulfides is discussed. We have identified two charged SN5 structures and three charged SN6 structures that can be good candidates for high-energy density materials.