Tungsten(0) and Rhenium(I) η2-Pyrrole Complexes: Dearomatization of Pyrroles and Their Facile Isomerizations, Protonations, and Reductions

Complexes of the form TpRe(CO)(MeIm)( η 2 -L) and TpW(NO)(PMe 3 )( η 2 -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 η 2 -1 H - or an η 2 -3 H -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 η 2 -pyrrole complexes and the reduction of the resulting pyrrolium species have also been investigated.