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Abstract: Upon mild heating (60–65°C), electron-deficient [Os3(CO)9(μ3-C7H4NS)(μ-H)] (1) readily adds to the activated alkyne, RChsp sp="0.25" />=CO2Me), to give two isomers of the alkenyl complexes, [Os3(CO)9(μ-C7H4NS)(μ3-RCCHR)] (2 and 3), differing in the orientation of the benzothiazole ligand. In both the alkenyl ligand acts as a five-electron donor binding through both carbons and one of the oxygen atoms of the substituents, which adopt a relative cis disposition. Heating 2 cleanly affords 3 suggesting that the former is the kinetic product and the latter is thermodynamically favoured. At higher temperatures (110°C), 3 rearranges to a third isomer [Os3(CO)9(μ-C7H4NS)(μ-RCCHR)] (4) which differs in the binding mode of the alkenyl ligand and where the alkyne substituents are in a relative trans disposition. A second product of this reaction is [Os3(CO)8(μ-OCH3){μ3-C7H4NSC(R)C}(μ-H)] (5) which results from the loss of two moles of CO, carbon–carbon coupling between hydrocarbyl and benzothiazole ligands and carbon–hydrogen addition to the triosmium centre. All new clusters are characterized by a total of 50 valence electrons and contain two metal–metal bonds as shown by single crystal X-ray diffraction studies. [Copyright &y& Elsevier]

Abstract: Treatment of unsaturated [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] (2) with t BuNC at room temperature gives [Os3(CO)8(CNBu t )){μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] (3) which on thermolysis in refluxing toluene furnishes [Os3(CO)7(CNBu t ){μ3-Ph2PCHP(Ph)C6H4}(μ-H)2] (4). Reaction of the labile complex [Os3(CO)9(μ-dppm)(NCMe)] (5) with t BuNC at room temperature affords the substitution product [Os3(CO)9(μ-dppm)(CNBu t )] (6). Thermolysis of 6 in refluxing toluene gives 4. On the other hand, the reaction of unsaturated [Os3(CO)9{μ3-η2-C7H3(2-Me)NS}(μ-H)] (7) with t BuNC yields the addition product [Os3(CO)9(CNBu t ){μ-η2-C7H3(2-Me)NS}(μ-H)] (8) which on decarbonylation in refluxing toluene gives unsaturated [Os3(CO)8(CNBu t ){μ3-η2-C7H3(2-Me)NS}(μ-H)] (9). Compound 9 reacts with PPh3 at room temperature to give the adduct [Os3(CO)8(PPh3)(CNBu t ){μ-η2-C7H3(2-Me)NS(μ-H)] (10). Compound 8 exists as two isomers in solution whereas 10 occurs in four isomeric forms. The molecular structures of 3, 6, 8, and 10 have been determined by X-ray diffraction studies. [Copyright &y& Elsevier]