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

The reaction of TpRu(CO)(NCMe)(Me) (1) and pyrrole forms TpRu(CO){κ²-N,N-(H)NC(Me)(NC₄H₃)} (2). The formation of complex 2 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 1. Mechanistic studies indicate that the most likely reaction pathway involves initial metal-mediated N−H activation of pyrrole to produce TpRu(CO)(N-pyrrolyl)(NCMe) (3) followed by C−C bond formation and proton transfer. Complex 3 has been independently prepared and demonstrated to convert to 2. Computational studies support the suggested selectivity for initial N−H bond cleavage in preference to C−H bond activation.