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 Fe-II-H complexes. Varying the L-type ligand on these complexes exhibited profound effects, as observed by IR and H-1 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 Fe-II-H complex with CO2 generated an Fe-formate complex (K-2-OOCH) from insertion into the Fe-II-H bond. The independent synthesis of this molecule was accomplished by treating Fe-II-Cl with excess NaOOCH.