Cobalt and Iron Stabilized Ketyl, Ketiminyl and Aldiminyl Radical Anions

Abstract

Carbonyl and iminyl based radical anions are reactive intermediates in a variety of transformations in organic synthesis. Herein, the isolation of ketyl, and more importantly unprecedented ketiminyl and aldiminyl radical anions coordinated to cobalt and iron complexes is presented. Insights into the electronic structure of these unusual metal bound radical anions is provided by X-Ray diffraction analysis, NMR, IR, UV/Vis and Mössbauer spectroscopy, solid and solution state magnetometry, as well as a by a detailed computational analysis. The metal bound radical anions are very reactive and facilitate the activation of intra-and intermolecular CÀ H bonds.

Intricate Road to Linear Anionic Nickel(I) Hexamethyldisilazanide [Ni(N(SiMe3)2)2]−

“…They are highly reactive, as expected from thefor these metalslow oxidation state in conjunction with the low-coordinate environment. As such, they have been exploited for a number of different reactivities such as C–F bond cleavage, , C–C multiple bond transformation, − reduction, , and a platform for either low-coordinate π-acceptor adducts (CO or alkynes), ,, imido, or chalcogenido complexes . Given the multifaceted use of these linear compounds, we were naturally interested in the respective nickel­(I) complex, which constitutes the heaviest open-shell linear metal­(I) hexamethyldisilazanide.…”

Iron(II) Mediated Deazotation of Benzyl Azide: Trapping and Subsequent Transformations of the Benzaldimine Fragment

“…To probe additional reactivity of HNCHPh we subjected the cis -divacant octahedral complex 1 -HNCHPh to one electron reduction. Our recent report of N 2 binding following KC 8 reduction of 1 -OEt 2 allowed us to pose the question of how the nature of the coordinating ligand affects its reduction chemistry and whether an aldimine radical anion, [HNCHPh] −• , could be formed. Accordingly, when a toluene solution of 1 -HNCHPh was treated with one equivalent of KC 8 , suspended in diethyl ether at room temperature, a color change of the solution to red-orange was observed after a couple of hours.…”

Taming the stilbene radical anion

“…39 The radical anionic nature of 1 was substantiated further chemically as it (incompletely) reduces [Co II (NR 2 ) 2 ] to the linear cobalt(I) complex [Co I (NR 2 ) 2 ] -(Figure S8) whose reduction potential (E red = -1.45 V vs Fc/Fc + ) is less than of the stilbene (E 1/2 (Z-stilbene) = -2.67 V; E 1/2 (E-stilbene) = -2.70 V vs Fc/Fc + ). 29,50,52 Journal Name…”

“…The spectrum of 3 at 13 K shows a doublet signal for the main species with an isomer shift of  = 0.53 mms -1 and a quadrupole splitting of Q = 1.44 mms -1 . The isomer shift corresponds very well with low coordinate iron(II) complexes ([Fe(NR 2 ) 3 ] -:  = 0.59 mms -1 , Q = 0.60 mms -1 ; [Fe(NR 2 ) 2 I] -:  = 0.63 mms -1 , Q = 0.60 mms -1 ; [Fe(NR 2 ) 2 OCPh 2 (•) ] (-) :  = 0.62 mms -1 , Q = 1.20/1.83 mms -1 ) 52,56,69 . The Mössbauer data implicates the formulation of 3 as an iron(II) bound alkene radical anion.…”

“…This signal position exhibits a slight high-field shift in comparison to either trigonal -alkyne iron or three-coordinate iron(II) hexamethyldisilazanides (-1.88 to -4.05 ppm). 52,57,67 Additional resonances at 92.7 ppm, 91.2 ppm and -25.3 ppm are attributed to aromatic substrate protons. Importantly, dissolution of pristine 3 gave rise to a signal belonging to the initially employed [Fe(NR 2 ) 2 ]as well as E-stilbene.…”