Tungsten(0) and Rhenium(I) <i>η</i>²-Pyrrole Complexes: Dearomatization of Pyrroles and Their Facile Isomerizations, Protonations, and Reductions

Complexes of the form TpRe(CO)(MeIm)(η2-L) and TpW(NO)(PMe3)(η2-L) have been synthesized, where L = 1-methylpyrrole, 2-methylpyrrole, and 2,5-dimethylpyrrole. Depending on the nature of both the pyrrole and the metal, either a η2-1H- or an η2-3H-pyrrole complex can be isolated. In contrast, for the parent pyrrole, oxidative addition occurs across the N−H bond, generating either a N-pyrrolyl or N-pyrrolyl hydride. The protonation or methylation of the η2-pyrrole complexes and the reduction of the resulting pyrrolium species have also been investigated.