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Carbon−Sulfur Bond Cleavage of Methyl-Substituted Thiophenes with Iridium(III)

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journal contribution
posted on 11.05.2009, 00:00 by Matthew R. Grochowski, William W. Brennessel, William D. Jones
Reaction of [Cp*IrHCl]2 (Cp* = η5-C5Me5) with 2-methylthiophene and 2,5-dimethylthiophene at 120 °C in the presence of H2 results in the cleavage of the thiophene carbon−sulfur bond(s). In both cases the thiophenes are ring-opened and hydrogenated, resulting in dinuclear Ir complexes with bridging thiolates. The primary product in the reaction involving 2,5-dimethylthiophene is [Cp*IrCl]2(μ-H)(μ-S-2-hexyl). This product has been characterized and is present in diastereomeric pairs. In the reaction with 2-methylthiophene a complex mixture consisting of five products is produced. The product distribution consists of mono- and disubstituted bridging thiolate complexes, three of which have been structurally characterized by single-crystal X-ray diffraction. Independent synthesis of each of these products has been performed, and characterization of the reaction mixture has been accomplished by 1H and 13C NMR spectroscopies, as well as by ESI-MS and elemental analysis. Reaction with 2-acetylthiophene showed very similar reactivity; an X-ray structure confirmed the nature of the diastereomeric pairs present.

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