EXTRUSION OF SELENIUM AND TELLURIUM ATOMS FROM SELENOPHENE AND TELLUROPHENE BY REACTION WITH TRINUCLEAR IRON, RUTHENIUM, AND OSMIUM CLUSTERS - CRYSTAL-STRUCTURES OF [OS6(MU-H)(MU-3-SE)(MU-4-C4H3)(CO)20] AND OF [RU4(MU-3-SE)MU-C4H4)(CO)11]

The trinuclear carbonyl clusters [Fe3(CO)12], [Ru3(CO)12], [Os3(CO)11(MeCN)], and [Os3(CO)10(MeCN)2] react with selenophene and tellurophene (cyclo-C4H4X, X = Se or Te) under mild conditions to give compounds containing the open-chain ligands CHCHCHCHX or the fragments X, C4H4, C4H3, or H as bridging ligands. The following compounds were isolated and characterised: [Os3(CO)10(C4H4X)], 1 where X = Se (X-ray structure reported previously) and 8 where X = Te, [Os6H(Se)(C4H3)(CO)20], 2, [Os2(CO)6(C4H4Se)], 3, [Ru2(CO)6(C4H4)], 4, [Ru4(Se)(CO)11(C4H4)], 5, [Fe2(CO)6(C4H4)], 6, and [Fe2(CO)6(C4H4Se)], 7. The clusters 2 and 5 were shown by single-crystal X-ray diffraction methods to have had both Se-C bonds broken to give mu-3-Se ligands in each case. Compound 2 contains an interesting mu-4-C4H3 ligand linking two Os3 units through a mu-alkylidyne bridge, a sigma-Os-C bond, and an eta-3-allyl component. Compound 5 has a mu-C4H4 ligand of a type previously found to be formed by alkyne coupling. The other compounds were characterised spectroscopically.