Ruthenium(II)-Mediated Carbon−Carbon Bond Formation between Acetonitrile and Pyrrole:  Combined Experimental and Computational Study

The reaction of TpRu(CO)(NCMe)(Me) (<b>1</b>) and pyrrole forms TpRu(CO){κ<sup>2</sup>-<i>N,N</i>-(H)NC(Me)(NC<sub>4</sub>H<sub>3</sub>)} (<b>2</b>). The formation of complex <b>2</b> involves the cleavage of the N−H bond and 2-position C−H bonds of pyrrole as well as a C−C bond forming step between pyrrole and the acetonitrile ligand of <b>1</b>. Mechanistic studies indicate that the most likely reaction pathway involves initial metal-mediated N−H activation of pyrrole to produce TpRu(CO)(<i>N</i>-pyrrolyl)(NCMe) (<b>3</b>) followed by C−C bond formation and proton transfer. Complex <b>3</b> has been independently prepared and demonstrated to convert to <b>2</b>. Computational studies support the suggested selectivity for initial N−H bond cleavage in preference to C−H bond activation.