Synthesis and Characterization of a Sterically Encumbered Homoleptic Tetraalkyliron(III) Ferrate Complex

Microscopic Reactivity of Phenylferrate Ions toward Organyl Halides

Despite its practical importance, organoiron chemistry remains poorly understood due to its mechanistic complexity. Here, we focus on the oxidative addition of organyl halides to phenylferrate anions in the gas phase. By mass-selecting individual phenylferrate anions, we can determine the effect of the oxidation state, the ligation, and the nuclearity of the iron complex on its reactions with a series of organyl halides RX. We find that Ph₂ Fe(I)^- and other low-valent ferrates are more reactive than Ph₃ Fe(II)^- ; Ph₄ Fe(III)^- is inert. The coordination of a PPh₃ ligand or the presence of a second iron center lower the reactivity. Besides direct cross-coupling reactions resulting in the formation of RPh, we also observe the abstraction of halogen atoms. This reaction channel shows the readiness of organoiron species to undergo radical-type processes. Complementary DFT calculations afford further insight and rationalize the high reactivity of the Ph₂ Fe(I)^- complex by the exothermicity of the oxidative addition and the low barriers associated with this reaction step. At the same time, they point to the importance of changes of the spin state in the reactions of Ph₃ Fe(II)^- .

Iron-Catalyzed Reductive Coupling of Alkyl Iodides with Alkynes To Yield cis-Olefins: Mechanistic Insights from Computation

In a recent study, a new procedure for Z-selective olefin synthesis by reductive coupling of alkyl iodides with terminal alkynes in the presence of iron salts is described. This transformation is representative of many newly developed synthetic routes through the involvement of multiple species and phases, which makes mechanistic insight hard to obtain. Here, we report computational work aimed at exploring the possible reaction pathways. DFT calculations lead to two suggested routes, one involving C-I reduction by metallic zinc and radical addition to the alkyne and the other involving addition of two reduced iron species to the alkyne bond followed by reductive elimination. Comparison to experimental results as well as kinetic modeling is used to discuss the likelihood of these and related mechanisms.