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Halide Effects on the Stability of Osmium Indenylidene Complexes: Isolation, Characterization, and Reactivities

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posted on 15.05.2020, 19:04 by Mingxu Cui, Xueying Guo, Herman H. Y. Sung, Ian D. Williams, Zhenyang Lin, Guochen Jia
[(η6-p-cymene)­OsI2]2 was found to be a good catalyst for the cyclopropanation reaction of isobutyl vinyl ether with 3-tert-butyldiazoindene. In contrast, the complexes [(η6-p-cymene)­OsX2]2 (X = Cl, Br) are poorer catalysts for the reaction. The interesting halide effect can be related to the tendency of osmium indenylidene complexes [(η6-p-cymene)­OsX2(indenylidene)] (6) (derived from the reactions of [(η6-p-cymene)­OsX2] (5) with diazoindene, X = Cl, Br, I) to undergo migratory insertion reactions to give η5-haloindenyl complexes. While the chloro indenylidene complex 6Cl readily rearranges to the corresponding η5-chloroindenyl complex 8Cl, the iodo indenylidene complex 6I can be stored in solutions for weeks without appreciable decomposition. The thermal stability of the bromo indenylidene 6Br is between those of Cl- and I-substituted indenylidenes. Computational studies have been carried out to understand the experimental observations. The indenylidene complexes described here represent the first well-characterized mononuclear indenylidene complexes synthesized from diazoindene precursors.

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