Catalytic Cyclooligomerization of Thietane by Tetraosmium and Tetraruthenium Tetrahydride Carbonyl Cluster Complexes

Abstract

The new compounds, Os{sub 4}(CO){sub 11}(SCH{sub 2}CH{sub 2}CH{sub 2} )({mu}-H){sub 4}, 3, Os{sub 4}(CO){sub 11}(12S3)({mu}-H){sub 4}, 4, Ru{sub 4} (CO){sub 11}(SCH{sub 2}CH{sub 2}CH{sub 2})({mu}-H){sub 4}, 5, and Ru{sub 4} (CO){sub 11}(12S3)({mu}-H){sub 4}, 6 (12S3 = 1,5, 9-trithiacyclododecane) have been obtained from the reactions of Os{sub 4}(CO){sub 11}(NCMe)({mu}-H){sub 4} and Ru{sub 4}(CO){sub 12} ({mu}-H){sub 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-hexathiacyclotetracosane) 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 wasmore » significantly lower, and analysis after the reactions showed that most of the cluster complexes had decomposed. 17 refs., 2 figs., 5 tabs.« less