PartialDeoxygenative CO Homocoupling By a Diiron Complex.

Abstract

One route to address climate change is converting carbon dioxide to synthetic carbon-neutral fuels. Whereas carbon dioxide to CO conversion has strong precedent in homo- and heterogeneous catalysis, deoxygenative coupling of CO to products with C-C bonds-as in liquid fuels-remains challenging. Here, we report coupling of two CO molecules by a diiron complex. Reduction of Fe2(CO)2L (2), where L2- is a bis(β-diketiminate) cyclophane, gives [K(THF)5][Fe2(CO)2L] (3), which undergoes silylation to Fe2(CO)(COSiMe3)L (4). Subsequent C-OSiMe3 bond cleavage and C=C bond formation occurs upon reduction of 4, yielding Fe2(μ-CCO)L. CO derived ligands in this series mediate weak exchange interactions with the ketenylidene affording the smallest J value, with changes to local metal ion spin states and coupling schemes (ferro- vs. antiferromagnetism) based on DFT calculations, Mossbauer and EPR spectroscopy. Finally, reaction of 5 with KEt3BH or methanol releases the C2O2- ligand with retention of the diiron core.