Two Schiff base ligands, 2-fE-[(5-phenyl-6H-1,3,4-thiadiazin-2yl)imino]methyneg-1-naphthol (L 1 H) and 5-nitro-2-f[(5-phenyl-6H-1,3,4-thiadiazin-2-yl)imino]methynegphenol (L 2 H) have been prepared from 5-phenyl-6H-1,3,4-thiadiazin-2-amine ðAÞ, 2-hydroxynaphthaldehyde (1) and 2-hydroxy-5-nitrobenzaldehyde (2) Mononuclear Co(II), Ni II and Cu II complexes of the ligands have been prepared by using Co II , Ni II and Cu II salts with a 1:2 metal:ligand ratio. It was determined that the bidentate behavior of the ligands is accomplished via the phenolic oxygen and the azomethine nitrogen atoms. The structures of the ligands and their complexes were identified by using elemental analyses, i.r., 1 H-n.m.r. spectra, electronic spectra, magnetic susceptibility measurements and thermogravimetric analyses (t.g.a.).