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Experimental and Computational Studies on the Iridium Activation of Aliphatic and Aromatic CH Bonds of Alkyl Aryl Ethers and Related Molecules

2009; Wiley; Volume: 15; Issue: 36 Linguagem: Inglês

10.1002/chem.200900646

1521-3765

Patricia Lara, Margarita Paneque, Manuel L. Poveda, Laura L. Santos, José E. V. Valpuesta, Ernesto Carmona, Salvador Moncho, Gregori Ujaque, Agustı́ Lledós, Eleuterio Álvarez, K. Mereiter,

Cyclopropane Reaction Mechanisms

Reaction of the Ir(III) complex [(Tp(Me2))Ir(C(6)H(5))(2)(N(2))] (1N(2)) with ortho-cresol (2-methylphenol) occurs with cleavage of the O-H and two C(sp(3))-H bonds of the phenol and formation of the electrophilic hydride alkylidene derivative [(Tp(Me2))Ir(H){=C(H)C(6)H(4)-o-O}] (2). The analogous reaction of 2-ethylphenol gives a related product 3. Both 2 and 3 have been shown to be identical to the minor, unidentified products of the already reported reactions of 1 with anisole and phenetole, respectively. Thus, in addition to the route that leads to the known heteroatom-stabilized hydride carbene [(Tp(Me2))Ir(H){=C(H)OC(6)H(4)-o-}] (B), anisole can react with 1 with cleavage of the O-CH(3) bond and formation of a new carbon-carbon bond. In contrast, only C-H bond-activation products with structures akin to B result from 1N(2) and 3,5-dimethylanisole (complex 8) or 4-fluoroanisole (9). Using anisole as a model, a computational study of the triple C-H bond activation (two aliphatic C-H bonds plus an ortho-metalation reaction) that is responsible for the formation of these heteroatom-stabilized hydride carbenes has been undertaken.