The ruthenium-tin complex, [Ru₂(CO)₄(SnPh₃)₂(μ-pyS)₂] (1), the main product of the oxidative-addition of pySSnPh₃ to Ru₃(CO)₁₂ in refluxing benzene, is [Ru(CO)₂(pyS)(SnPh₃)] synthon. It reacts with PPh₃ to give [Ru(CO)₂(SnPh₃)(PPh₃)(μ-pyS)] (2) and further with Ru₃(CO)₁₂ or [Os₃(CO)₁₀(NCMe)₂] to afford the butterfly clusters [MOs₃(CO)₁₂ (SnPh₃)(μ₃-pyS)] (3-4). Direct addition of pySSnPh₃ to [Os₃(CO)₁₀(NCMe)₂] at 70°C gives [Os₃(CO)₉(SnPh₃)(μ₃-pyS)] (5) as the only bimetallic compound, while with unsaturated [Os₃(CO)₈{μ₃-PPh₂CH₂P(Ph)C₆H₄}(μ-H)] the previously reported [Os₃(CO)₈(μ-pyS)(μ-H)(μ-dppm)] (6) and the new bimetallic cluster [Os₃(CO)₇(SnPh₃){μ-Ph₂PCH₂P(Ph)C₆H₄}(μ-pyS)[(μ-H)] (7) are formed at 110°C. Compounds 1, 2, 4, 5 and 7 have been characterized by X-ray diffraction studies.