The reaction of gaseous H2S with aqueous ammonium heptamolybdate in the presence of triethylenetetramine (trien) gave a red complex. The complex was recrystallized in hot water and characterized by element analysis and UV, visible, IR, and 1H NMR spectroscopy. PMR has revealed accidental magnetic equivalence, resulting from the proximity of [MoS4] 2- species in one complex molecule to the open triethylenetetramine ligand of another molecule. (TrienH2)[MoS4] crystallizes in the orthorhombic crystal system, space group Pca21, a = 13.045(2), b = 16.461(3), c = 13.754(2) Å, α = 90, β = 90, γ = 90°, V = 2953.5(9) Å3, Z = 8, R1 = 0.0323, wR2 = 0.0730. The structure consists of the tetrahedral tetrathiomolybdate anions, forming an extended 3D framework in solids due to the interactions with triene cations via Mo-S...H-N hydrogen bonds.