Reactions of M2(CO)10 (M = Re, Mn) with pyrimidine-2-thiol (pymSH) in the presence of Me3NO afford the tetranuclear square-type complexes [M4(CO)12(μ-κ3-pymS)4] (1, M = Re; 2, M = Mn). Both consist of four M(CO)3 (M = Re, Mn) units, pairs of which are joined by tridentate pyrimidine-2-thiolate ligands. Treatment of 1–2 with a variety of donor ligands results in cleavage of the square to afford mononuclear species with either a mono- or bidentate pyrimidine-2-thiolate ligand. Triphenylphosphine reacts with 2 to give [Mn(CO)3(PPh3)(κ2-pymS)] (3) in which the pyrimidine-2-thiolate coordinates in a bidentate fashion. With diamines [M(CO)3(κ2-L)(κ1-pymS)] (4–7) (M = Re, Mn; L = 2,2′- bipy, 1,10-phen, en) result in which the pyrimidine-2-thiolate binds in a monodentate fashion through sulfur. With diphosphines, complexes with different stoichiometries and pyrimidine-2-thiolate binding modes are obtained depending on the nature of the metal and diphosphine. With dppm and dppe, 1 gives [Re(CO)2(κ1-pymS)(κ2-dppm)] (8) and [Re(CO)2(κ2-pymS)(κ1-dppe)2] (10), respectively, whereas 2 affords [Mn(CO)2(κ2-pymS)(κ1-dppm)2] (9) and [Mn(CO)2(κ2-pyS)(κ2-dppe)] (11) under similar conditions. Reactions of 1–2 with [Os3(CO)10(NCMe)2] affords mixed-metal butterfly clusters [MOs3(CO)13(μ3-κ2-pymS)] (12–13) in which the group 7 metal occupies a wing-tip position and the pyrimidine-2-thiolate ligand caps a triangular Os2M face. With Ru3(CO)12, carbon–sulfur bond cleavage occurs to give the tetranuclear clusters [MRu3(CO)14(μ4-S)(μ-κ1:η1-pym)] (14–15) bearing both the extruded sulfur and the heterocyclic ring. The molecular structures of 1–7, 10 and 12 have been established by X-ray diffraction allowing the binding mode of the pyrimidine-2-thiolate ligands to be probed.