Synthesis and Characterization of (DIPPCCC)Fe Complexes: A Zwitterionic Metalation Method and CO2 Reactivity

The synthesis and characterization of a series of novel iron complexes has been accomplished using a monoanionic pincer bis(carbene) ligand framework. Metalation first proceeded through an isolated Fe(II) zwitterionic intermediate that was subsequently reduced in situ to Fe(0) to facilitate oxidative addition of the aryl C–H bond, generating the FeII–H complexes. Varying the L-type ligand on these complexes exhibited profound effects, as observed by IR and 1H NMR spectroscopy. Higher oxidation states of Fe could also be supported in this ligand framework, as evidenced by the isolation of two Fe(III) complexes. Treating an FeII–H complex with CO2 generated an Fe–formate complex (κ2-OOCH) from insertion into the FeII–H bond. The independent synthesis of this molecule was accomplished by treating FeII–Cl with excess NaOOCH.