Selective CÀC σ-bond activation (cleavage) by transitionmetal complexes is one of the most challenging subjects in organometallic chemistry. This is due not only to its fundamental scientific interest, but also its potential utility in organic synthesis.[1] In general, this transformation depends heavily on either the release of ring strain or aromatization to provide the substantial driving force and thus lacks generality.[2] As an exception, CÀCN σ ...