The reactions of the tridentate Schiff-base ligand derived from salicylaldehyde and o-aminothio-phenol (H₂L¹) with [MOCl₄]^–(M = Tc or Re) have been investigated. The complexes [MOCl(L¹)], [ReOCl₂(L¹)]^–, and [ReOCl(X)(L¹)](X = MeOH or EtOH) were synthesized and characterized by elemental analysis, i.r., ¹H n.m.r., and u.v.–visible spectroscopy, mass spectrometry, magnetic susceptibility, conductivity, and thermogravimetric measurements and the complete configurations of the complexes were determined. X-Ray crystallographic investigation on [TcOCl(L¹)] shows the molecular structure to be a distorted square pyramid having the ligand L¹ in the equatorial plane with respect to TcO. The molecule is in the monoclinic space group P2₁/a, with a= 14.255(9)b= 12.495(7), c= 7.865(6)Å, β= 105.22(5)°, and Z= 4. The structure has been refined to R= 0.068 for 2 184 observed reflections. The reactions of [MOCl(L¹)](M = Tc or Re) or [ReOCl(X)(L¹)](X = MeOH or EtOH) with the bidentate Schiff-base ligands (HL) salicylideneimine (HL³), N-methylsalicylideneimine (HL⁴), N-phenylsalicylidene-imine (HL⁵), N-(2-hydroxyphenyl)-p-nitrobenzylideneimine (HL⁶), quinolin-8-ol (Hquin), quinoline-8-thiol (Htquin), and N-(2-mercaptophenyl)-p-nitrobenzylideneimine (HL⁷) lead to the ‘mixed’ compounds [MO(L¹)(L)]. The products with L = tquin or L⁷ were obtained only for [ReOCl(X)(L¹)](X = MeOH or EtOH). All these complexes were characterized by the physicochemical techniques listed above.