For monometallic systems the direct oxidative addition of the sp 2 C-H bond in an unactivated alkene is hard to achieve. This is well documented and can be rationalized by the competing πcoordination of the alkene over the formation of a weakly bound σ-C-H complex vital for the bond cleavage at the transition metal centre. By contrast, our findings suggest that alkene binding is essential for the C-H activation to take place in the present bimetallic system. The (2+2) cycloaddition of the styrene substrates is weak and appears to initiate a low energy pathway for C-H activation. We identified an unusual transition state connecting the alkene complex with the final hydrido vinyl product. This key step proceeds through a highly asynchronous transition state near the boundary between a concerted/stepwise mechanism influenced by the resonance stabilization ability of the aryl substituent. Moreover, the geometry of the transition state results in the selective metalation of the (E)-β-C-H bond of the substrate. This concept might stimulate future developments towards catalytic C-H functionalization reactions.