C–C σ-Bond Oxidative Addition and Hydrofunctionalization by a Macrocycle-Supported Diiron Complex
Tianchang Liu, Ryan P. Murphy, Patrick J. Carroll, Michael R. Gau, Neil C. Tomson
Abstract
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 ([Fe2N2]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, iPr, tBu), 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 [Fe2N2]0, thereby completing synthetic cycles for C–C σ-bond functionalization.