title: Reversible C-C bond formation between redox-active pyridine ligands in iron complexes.
abstract: This manuscript describes the formally iron(I) complexes L(Me)Fe(Py-R)(2) (L(Me) = bulky β-diketiminate; R = H, 4-tBu), in which the basal pyridine ligands preferentially accept significant unpaired spin density. Structural, spectroscopic, and computational studies on the complex with 4-tert-butylpyridine ((tBu)py) indicate that the S = 3/2 species is a resonance hybrid between descriptions as (a) high-spin iron(II) with antiferromagnetic coupling to a pyridine anion radical and (b) high-spin iron(I). When the pyridine lacks the protection of the tert-butyl group, it rapidly and reversibly undergoes radical coupling reactions that form new C-C bonds. In one reaction, the coordinated pyridine couples to triphenylmethyl radical, and in another, it dimerizes to give a pyridine-derived dianion that bridges two iron(II) ions. The rapid, reversible C-C bond formation in the dimer stores electrons from the formally reduced metal as a C-C bond in the ligands, as demonstrated by using the coupled diiron(II) complex to generate products that are known to come from iron(I) precursors.
authors.affiliation: Department of Chemistry, University of Rochester, Rochester, New York, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Dugan
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: K Cory
authors.initials: KC
authors.lastname: MacLeod
authors.forename: Gemma J
authors.initials: GJ
authors.lastname: Christian
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Cowley
authors.forename: William W
authors.initials: WW
authors.lastname: Brennessel
authors.forename: Shengfa
authors.initials: S
authors.lastname: Ye
authors.forename: Frank
authors.initials: F
authors.lastname: Neese
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Holland