Experimental and computational studies on the iridium activation of aliphatic and aromatic C-H bonds of alkyl aryl ethers and related molecules

Reaction of the Ir111 complex [(TpMe2)Ir(C 6H5)2(N2)] (1-N2) 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 [(TpMe2)Ir(H){= C(H)C6H 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 re ported reactions of 1 with anisole and phenetole, respectively. Thus, in addition to the route that leads to the known heteroatom-stabilized hydride carbene [(TpMe2)Ir(H){=C(H)OC 6H4o-}] (B), anisole can react with 1 with cleavage of the O-CH3 bond and for- mation of a new carbon-carbon bond. In contrast, only C-H bond-activation products with structures akin to B result from 1-N2 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. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.