The power of oriented electrostatic fields (ESFs) to influence chemical bonding and reactivity is a phenomenon of rapidly growing interest. The presence of strong ESFs has recently been implicated as...

This report describes the first examples of unassisted C­(sp)–C­(sp2) and C­(sp)–C­(sp3) bond oxidative addition reactions to give thermodynamically favorable products. Treatment of a diiron complex supported by a geometrically and electronically flexible macrocyclic ligand, (3PDI2)­Fe2(μ-N2)­(PPh3)2 ([Fe 2 N 2 ] 0 ), with stoichiometric amounts of various 4,4′-disubstituted diphenylacetylenes (ArX–CC–ArX; X = OMe, H, F, CF3) yielded C­(sp)–C­(sp2) bond oxidative addition products. When Ph–CC–R substrates were used as substrates (R = Me, Et, i Pr, t Bu), products of either C­(sp)–C­(sp2) or C­(sp)–C­(sp3) bond activation were obtained, with the less sterically encumbering alkynes exclusively undergoing C­(sp)–C­(sp3) bond activation. Treatment of the C–C activation species with either H2 or HBpin was found to form products of C–C σ-bond hydrofunctionalization. In both the hydrogenation and hydroboration schemes, the diiron species was observed to return to [Fe 2 N 2 ] 0 , thereby completing synthetic cycles for C–C σ-bond functionalization.