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(-H)(CO)10{(-n-(C 4H3S)(C8H4S)}] (1) and [Os 3(-H)(CO)10{(3-n2- n1-n1-(SC7H4)C(SC 4H3)}] (2), whereas in the analogous case of 1,4-bis(3-thienyl)butadiyne the main coordination product was found to be [Os3(-H)(CO)10{(-n-(C4H 3S)(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(-H)(CO) 9{(3-n3-(C4H 3S)(C8H4S)}] (4) and [Os3(-H) 2(CO)9{(3-n1- n1-(C4H3S)(C8H3S)}] (5). Thermal decarbonylation of 2 yielded [Os3(-H)(CO) 9{(3-n3-(C4H 3S)(C8H4S)}] (6), while thermal decarbonylation of 3 yielded [Os3(-H)(CO)9{(3- n3-(C4H3S)(C8H4S)}] (7). A reaction involving 3 with CF3COOH affords as the main cluster product the known cluster [Os3(-H)(CO)10(O 2CF3)] (8) and, unusually, permits the isolation and characterization of the novel organic molecule [(C4H 3S)(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.