Oxidative Addition of Carbon–Carbon Bonds with a Redox-Active Bis(imino)pyridine Iron Complex

Abstract

Addition of biphenylene to the bis(imino)pyridine iron dinitrogen complexes, (iPrPDI)Fe(N2)2 and [(MePDI)Fe(N2)]2(μ2-N2) (RPDI = 2,6-(2,6-R2—C6H3— N=CMe)2C5H3N; R = Me, iPr), resulted in oxidative addition of a C—C bond at ambient temperature to yield the corresponding iron biphenyl compounds, (RPDI)Fe-(biphenyl). The molecular structures of the resulting bis-(imino)pyridine iron metallacycles were established by X-ray diffraction and revealed idealized square pyramidal geometries. The electronic structures of the compounds were studied by Mössbauer spectroscopy, NMR spectroscopy, magnetochemistry, and X-ray absorption and X-ray emission spectroscopies. The experimental data, in combination with broken-symmetry density functional theory calculations, established spin crossover (low to intermediate spin) ferric compounds antiferromagnetically coupled to bis(imino)pyridine radical anions. Thus, the overall oxidation reaction involves cooperative electron loss from both the iron center and the redox-active bis(imino)pyridine ligand.

Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

“…9,10,11 By enabling cooperative metal-ligand redox events, net two-electron chemistry can be achieved while the metal engages in only one-electron processes. 12 This concept, important in the function of many metalloenzymes, 13 has emerged as an effective strategy in base metal catalysis, 2a,10,12,14,15 small molecule activation and group transfer chemistry. 16,17 …”

Redox‐Active Ligand‐Induced Homolytic Bond Activation

“…[8] Installment as a redox-innocent entity adjacent to a redox-active framework is less likely to affect the coordinative properties at phosphorus, but relatively few of these ligands have been developed. [11][12][13][14] Metal-mediated one-electron homolysis is much rarer, [15] while reductive homolytic bond fission originating from ligand-based overall singleelectron transfer is, to the best of our knowledge, unknown ( Figure 1). Established ligand-mediated bond activation (and formation) reactions classify overall as two-electron processes.…”

Synthesis, Characterization, and Reactivity of Iron(III) Complexes Supported by a Trianionic ONO3– Pincer Ligand

“…The ligand's accessibility to multiple oxidation states allows first row transition metals, frequently constrained to one-electron redox chemistry, to perform multiple electron redox reactions usually involved in bond-making and bond-breaking processes. 34,36,44 Using the monoanionic quinonate form of the ligand, Heyduk and co-workers synthesized an Fe(III) complex capable of disulfide reductive elimination, where the ligand …”