PNNL

Abstract

Protonation of the Fe diphosphine complex Fe(PEtNMePEt)(CO)3 (PEtNMePEt = (Et2PCH2)2NMe) by [(Et2O)2H][B(C6F5)4)] occurs at the metal to give the iron hydride [Fe(PEtNMePEt)(CO)3H]+[B(C6F5)4]-. In contrast, treatment with HBF4•OEt2 gives protonation at the iron and at the pendant amine. Both the FeH and NH tautomers were characterized by single crystal X-ray diffraction. Addition of [BF4]- to the equilibrium mixture leads to the NH tautomer being exclusively observed, due to N-H•••F hydrogen bonding. Treatment of Fe(PEtNMePEt)(CO)3 with excess HOTf gives a dicationic species where both the iron and nitrogen are protonated. Isomerization of the dicationic complex was studied by NOESY NMR spectroscopy. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory (PNNL) is operated by Battelle for the U.S. DOE. We thank Dr. Eric Walter for the EPR spectra. EPR experiments were performed using the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL.