Acid-Catalyzed Oxidative Addition of a C-H Bond to a Square Planar d(8) Iridium Complex

作者：Hackenberg Jason D; Kundu Sabuj; Emge Thomas J; Krogh Jespersen Karsten; Goldman Alan S^*

来源：Journal of the American Chemical Society, 2014, 136(25): 8891-8894.

DOI：10.1021/ja503953v

While the addition of C-H bonds to three-coordinate Ir(1) fragments is a central theme in the field of C-H bond activation, addition to square planar four-coordinate complexes is far less precedented. The dearth of such reactions may be attributed, at least in part, to kinetic factors elucidated in seminal work by Hoffmann. C-H additions to square planar carbonyl complexes in particular are unprecedented, in contrast to the extensive chemistry of oxidative addition of other substrates (e.g., H-2, HX) to Vaska's Complex and related species. We report that Bronsted acids will catalyze the addition of the alkynyl C-H bond of phenylacetylene to the pincer complex (PCP)Ir(CO). The reaction occurs to give exclusively the trans-C-H addition product. Our proposed mechanism, based on kinetics and DFT calculations, involves initial protonation of (PCP)Ir(CO) to generate a highly active five-coordinate cationic intermediate, which forms a phenylacetylene adduct that is then deprotonated to give product.

• 出版日期2014-6-25