New metallapyrrole complexes from [M2(μ-CNMe2)(μ-CO)(CO)2(Cp)2]SO3CF3 (M=Fe, Ru) and acetonitrile anions; structure of [(Cp)(CO)FeC(NMe2)N(H)C(Me)C(CN)]

The reaction of [M2{μ-CN(Me)R}(μ-CO)(CO)2(Cp)2]SO3CF3 (M=Fe, R=Me, 1a; M=Fe, R=CH2Ph 1b, M=Ru, R=CH2Ph, 1c) with a mixture of KH and acetonitrile affords [(Cp)(CO)(CN)] (2a–c). The X-ray structure of 2a (M=Fe, R=Me) shows the formation of a pyrrole-like metallaring (5). The double bond character of the C(4)C(5) interaction [1.309(7)] suggests the enammine nature of the N(H)C(Me)C(CN) fragment which originates from condensation of two acetonitrile molecules. A mechanism for the formation of 2a–c is proposed in light of the 13C-NMR and IR evidence. Complex 2a can be methylated at the N-end of the hexocyclic CN group, forming a cationic metallacyclo complex containing the CCN+Me nitrilium moiety.