Direct Synthesis of Iron(0) N-Heterocyclic Carbene Complexes by Using Fe3(CO)(12) and Their Application in Reduction of Carbonyl Groups

Iron Fe(NHC)(CO)(4) complexes were formed by direct reaction of Fe-3(CO)(12) with equimolecular amounts of NHC imidazolium halide precursors; addition of base was not needed in this reaction. When excess (9:1 ratio) 1,3dimesitylimidazolium chloride is reacted with the iron cluster Fe-3(CO)(12), a mixture of Fe(IMes)(CO)(4) and Fe(IMes)(2)(CO)(3) is obtained. Single crystals of Fe(IMes)(CO)(4) and crystals resulting from the cocrystallization of Fe(IMes)-(CO), and Fe(IMes)(2)(CO)(3) have been studied by X-ray diffraction. These iron(0) complexes were found to catalyze the reduction of benzaldehydes.