Pincer complexes of iridium such as the highly reactive 14-electron fragment tBuPCPIr (tBuPCP = {κ3-2,6-bis[(di-tert-butylphosphino)methyl]phenyl}) have been studied extensively, due to their effectiveness in selectively activating strong bonds in small molecules. Selectivity has been shown to depend, in part, on the steric bulk of the pincer ligand, but the electronic structure of the substrate also has a substantial effect. The simplest aromatic substrate, benzene, has perfectly symmetrical geometry and uniform electron density at all six C-H bonds; in the absence of substituents, these bonds add rapidly and reversibly to the tBuPCPIr fragment. With larger aromatic substrates such as naphthalene and its isomer azulene, however, the C-H bonds are no longer equivalent with respect to steric and electronic characteristics. The products of C-H addition reactions with these substrates are consistent with the expected trends; less hindered, more highly acidic C-H bonds are preferred in both cases. Characterization of the products of these reactions (and those of relevant derivatives) will be discussed.

Tales of two isomers: Probing the mechanism of C-H addition to tBuPCPIr by comparing the products of reactions with naphthalene and azulene

256th National Meeting (2018)

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