New Method for Intramolecular Cyclization of Osmium-Coordinated Diynes Avoiding Os3(μ-H)2(CO)10 as Starting Material

A new method of synthesis was carried out for the preparation of the hydride clusters [Os3(μ-H)(CO)9{μ3,η1:η3:η1-RC2COHC≡CR}] (R = C4H3S (1a), BrC4H2S (1b), Ph (1c)) by reaction between RC≡CC≡CR (R = C4H3S (a), BrC4H2S (b), Ph (c)) and the “non-hydride” [Os3(CO)11(CH3CN)] in dichloromethane at room temperature and in the presence of water, avoiding the starting material [Os3(μ-H)2(CO)10]. The complexes [Os3(μ-CO)(CO)9{μ3,η1:η2:η1-RC4R}] (R = C4H3S (2a), BrC4H2S (2b), Ph (2c)) were also obtained as byproducts. 1a−c and 2a−c contain a “closed” Os3 triangular core in μ3,η1:η3:η1-allylic and μ3,η1:η2:η1-alkyne coordination modes, respectively. When the reaction is carried out in wet polar and donor solvents [Os3(μ-H)(CO)9{μ3,η1:η3:η1-RC2CH═COCR}] (R = C4H3S (3a), BrC4H2S (3b), Ph (3c)) are obtained, where the organic ligand turns into a furan ring by an intramolecular cyclization process. These reactions proceed through 1a−c as intermediates, identified by 1H NMR. Therefore, 3a−c have also been obtained as th...