Aminocyclodiphosph(V)azane of thiazoline, III (1,3-diphenyl-2,4-bis(2-acetyl-2-thiazolinehydrazone)-2,2,4,4-tetrachlorocyclodiphosph(V)azane, reacts with stoichio-metric amounts of transition metal salts such as Co(II), Ni(II), and Cu(II) to afford coloured complexes in a moderate to high yield. The structure of the isolated complexes was suggested based on elemental analyses, IR, molar conductance, UV-Vis, ¹H and ³¹P NMR, solid reflectance, magnetic susceptibility measurements and dark electrical conductivity of solid state. The solid state electrical conductivity obtained reveals that the ligand (III) and its metal complexes behave as semiconducting materials. Most of the prepared compounds showed high bactericidal activity and, in some cases, the complexes have higher bactericidal activity than the ligand.