Coordination Behavior and Transformations of Thienyl-Substituted Diacetylenes upon Coordination to Os3H2(CO)10

The reaction between 2- and 3-thienyl-substituted 1,3-butadiynes and the electron-deficient osmium cluster Os3H2(CO)10 yields trinuclear coordination products, associated with transformations of the diacetylene ligands. Depending on the heteroaryl end groups, osmium clusters with both a closed and open Os-triangle core were formed. The reaction between Os3H2(CO)10 and 1,4-bis(2-thienyl)butadiyne yielded [Os3(μ-H)(CO)10{(μ-η-(C4H3S)(C8H4S)}] (1) and [Os3(μ-H)(CO)10{(μ3-η2-η1-η1-(SC7H4)C(SC4H3)}] (2), whereas in the analogous case of 1,4-bis(3-thienyl)butadiyne the main coordination product was found to be [Os3(μ-H)(CO)10{(μ-η-(C4H3S)(C8H4S)}] (3). Compounds 1–3 were stable in air, but lost carbon monoxide upon prolonged heating. Thermal decarbonylation of 1 under N2 yielded a mixture of [Os3(μ-H)(CO)9{(μ3-η3-(C4H3S)(C8H4S)}] (4) and [Os3(μ-H)2(CO)9{(μ3-η1-η1-(C4H3S)(C8H3S)}] (5). Thermal decarbonylation of 2 yielded [Os3(μ-H)(CO)9{(μ3-η3-(C4H3S)(C8H4S)}] (6), while thermal decarbonylation of 3 yielded [Os3(μ-H)(CO)9{(μ3-η3-(C4H3S)(C8H4S)}] (7). A reaction involving 3 with CF3COOH affords as the main cluster product the known cluster [Os3(μ-H)(CO)10(O2CF3)] (8) and, unusually, permits the isolation and characterization of the novel organic molecule [(C4H3S)(C8H4S)(OCF3)] (9) cleaved from the parent cluster. The structures of the new compounds were established by single-crystal X-ray studies and spectroscopic methods and supported by density functional theory.