Here we identify a single iron porphyrin catalyst that appears to mediate both alkene MHAT and capture of the resulting radical in an alkyliron SH2 (Fig 1c). This is an unusual and, to our knowledge, unprecedented type of alkene cross-coupling where a single metal catalyst mediates iterative outer-sphere bond-forming elementary steps, i.e. the catalytic metal center does not form a bond to the alkene in either bond-forming step. 11 Each alkene carbon would react with an iron catalytic intermediate where single electron density resides on a reacting ligand, as suggested previously. 12 Among the products of these cross-couplings are benzyl heterodimers, privileged motifs among drug substances that are difficult to access from two benzyl fragments, 13p-u especially to generate the quaternary carbons demonstrated here.