The treatment of [Ru3(CO)10(μ-dppm)] with 6-methyl-2-mercaptopyridine (1) or 5-trifluoromethyl-2-mercaptopyridine (2) in refluxing THF for 10 h results in the formation of μ5 sulfide-capped pentanuclear clusters [Ru5(CO)11(μ-H)(μ5-S){μ-κ2N,C-NC5H3(R)})(μ-κ2P2-dppm)2] (R = CH3, 3a, 3a'; R=CF3, 3b,3b') respectively. These compounds exhibit unique structural features, with a μ5-S capped binding trinuclear and dinuclear fragments. The mercaptopyridine ligands undergo S-C bond scission, forming an orthometalated pyridine ligand coordinated to a Ru-Ru bond with a concomitant μ-hydride ligand formation. The structures also feature two dppm ligands, one in the Ru-Ru, which bears the μ-H, and the other bridging the Ru-Ru bond with the orthometallated pyridine. In solution, linkage isomers were observed; they differ in the coordination position of the orthometallated pyridine bonded to the same Ru-Ru bond. A single-crystal X-ray diffraction study confirmed the molecular structures of compounds 3a and 3b. NMR, IR, and HRMS were also carried out.
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