Synthesis, electronic structure and reactivity of bis(imino)pyridine iron carbene complexes: evidence for a carbene radical

The reactivity of the disubstituted diazoalkane, N2CPh2 with a family of bis(imino)pyridine iron dinitrogen complexes was examined. For the most sterically protected member of the series, ((PDI)-P-iPr)Fe(N-2)(2) ((PDI)-P-iPr = 2,6-(2,6-(Pr2C6H3N)-Pr-i=CMe)(2)C5H3N), an S = 1 iron diazoalkane complex was obtained and structurally characterized. Reducing the size of the 2,6-aryl substituents to ethyl or methyl groups resulted in isolation of bis(imino)pyridine iron carbene complexes. Magnetic measurements established S = 1 ground states, demonstrating rare examples of iron carbenes in a weak ligand field. Electronic structure determination using metrical parameters from X-ray diffraction as well as Mossbauer, XAS and computational data established high-spin iron(s) compounds engaged in antiferromagnetic coupling with redox-active bis(imino)pyridine and carbene radicals.