CATALYTIC CYCLOOLIGOMERIZATION OF THIETANE BY TETRAOSMIUM AND TETRARUTHENIUM TETRAHYDRIDE CARBONYL CLUSTER COMPLEXES

The new compounds Os-4(CO)(11)(SCH2CH2CH2)(mu-H)(4), 3, Os-4(CO)(11)(12S3)(mu-H)(4), 4, Ru-4(Co)(11)(SCH2CH2CH2)(mu-H)(4), 5, and Ru-4(CO)(11)(12S3)(mu-H)(4), 6 (12S3 = 1,5,9-trithiacyclododecane) have been obtained from the reactions of Os-4(CO)(11)(NCMe)(mu-H)(4) and Ru-4(CO)(12) (mu-H)(4) with thietane and 12S3, respectively. The molecular structure of 4 was established by a single-crystal X-ray diffraction analysis. The molecule contains a tetrahedral cluster of four osmium atoms with four bridging hydride ligands and a 12S3 ligand coordinated to one of the metal atoms through one of its three sulfur atoms. Compounds 3 and 4 were found to be efficient catalysts for the cyclooligomerization of thietane to 12S3 and 24S6 (24S6 1,5,9,13,17,21-hexathiacyclotetraeosane) with a 6/1 preference for 12S3 after a 24 h reaction period. A kinetic study of the catalysis by 4 showed that the formation of 12S3 is first order in the concentration of 4, which is consistent with the catalysis being produced by a tetranuclear cluster complex. Significant amounts of 12S3 and 24S6 were also obtained from thietane when 5 and 6 were used as catalyst precursors; however, the selectivity for 12S3 was significantly lower, and analysis after the reactions showed that most of the cluster complexes had decomposed. Crystal data for 4: space group = C2/c, a = 29.904(6) Angstrom, b = 11.815(2) Angstrom, c = 17.633(3) Angstrom beta = 91,28(2)degrees, Z = 8, 3384 reflections, R = 0.058.