Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds

We report the formation and full characterization of weak adducts between Li+ and Na+ cations and a neutral iron(0) complex, [Fe(CO)(3)(PMe3)2] (1), supported by weakly coordinating [BAr20F] anions, [1.M][BA(F)(r)20] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)(3)(PMe3)(2)][BAr20F], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and crosscoupling reactions and the formation of new C-E bonds (E = C, H, O, N, S). Further, we utilize [1 center dot M][BAr20F] as a catalyst in a simple hydrodehalogenation reaction under mild conditions to showcase its potential use in catalytic reactions. Finally, the mechanism of activation is probed using DFT and kinetic experiments that reveal that the alkali metal and iron(0) center cooperate to cleave C-X via a mechanism closely related to intramolecular FLP activation.

Automated summary

In this study, weak adducts between Li+ and Na+ cations and a neutral iron(0) complex were reported, which synergistically activate aliphatic C-X bonds and lead to the formation of iron(II) organyl compounds. The system showed potential for homocoupling and crosscoupling reactions. Further investigation on the activation mechanism revealed a cooperation between the alkali metal and iron(0) center.