The oxidative addition of covalent bonds to square planar complexes has been an archetypal transformation since the initial studies of Vaska's complex, Ir(PPh3)2(CO)Cl.  But despite the wealth of square planar complexes available and the ubiquity of the C-H bond, examples of oxidative addition to C-H bonds are quite rare, while addition to square planar carbonyls is, to our knowledge, unprecedented. We report that Br�nsted acids catalyze addition of the C(sp)-H bond of phenylacetylene to the square-planar Ir-pincer complex, (PCP)Ir(CO), an analogue of Vaska's complex. The trans addition product is formed exclusively. Our proposed mechanism, based on kinetics and DFT calculations, involves initial protonation of (PCP)Ir(CO) to generate a highly active 5-coordinate cationic intermediate which forms a phenylacetylene adduct that is then deprotonated to give product. Synthesis, mechanism, kinetics, calculations, and implications for a broader range of substrates will be discussed.

Acid-catalyzed oxidative addition of C-H bonds to square-planar complexes

244th National Meeting (2012)

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