Two-state reactivity in C–H activation by a four-coordinate iron(0) complex

Hickey, Anne K.; Lutz, Sean A.; Chen, Chun-Hsing; Smith, Jeremy M.

doi:10.1039/c6cc09244f

Cited by 31 publications

(21 citation statements)

References 45 publications

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“…S23 – S25 ) support the difference, and density functional theory (DFT) studies indicate that the molecules have high-spin electronic configurations ( S = 1 for 3-K and S = 2 for 4-Na ). This is a rare case of room-temperature C–H activation using a high-spin iron complex 22 , 23 . Reduction of 2 with Na and 15-crown-5 in toluene similarly gave LFe(H)(Tol)Na(15c5), from activation of the aryl C–H bonds of the solvent.…”

mentioning

confidence: 95%

Coupling dinitrogen and hydrocarbons through aryl migration

McWilliams

Broere

Halliday

et al. 2020

Nature

112

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A persistent challenge in chemistry is to activate abundant, yet inert molecules such as hydrocarbons and atmospheric N 2 . In particular, forming C–N bonds from N 2 typically requires a reactive organic precursor 1 , which limits the ability to design catalytic cycles. Here, we report an diketiminate-supported iron system that is able to sequentially activate benzene and N 2 to form aniline derivatives. The key to this new coupling reaction is the partial silylation of a reduced iron-N 2 complex, which is followed by migratory insertion of a benzene-derived phenyl group to the nitrogen. Further reduction releases the nitrogen products, and the resulting iron species can re-enter the cyclic pathway. Using a mixture of sodium powder, crown ether, and trimethylsilyl bromide, an easily prepared diketiminate iron bromide complex 2 can mediate the one-pot conversion of several petroleum-derived compounds into the corresponding silylated aniline derivatives using N 2 as the nitrogen source. Numerous compounds along the cyclic pathway have been isolated and crystallographically characterized; their reactivity outlines the mechanism including the hydrocarbon activation step and the N 2 functionalization step. This strategy incorporates nitrogen atoms from N 2 directly into abundant hydrocarbons.

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confidence: 95%

Coupling dinitrogen and hydrocarbons through aryl migration

McWilliams

Broere

Halliday

et al. 2020

Nature

112

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“…In functional synthetic models, mononuclear iron complexes have been used to gauge the N 2 -coordinating ability of compounds with Fe-C bonds. 16,17,[23][24][25][26][27][28] 16,27,29 Studies of iron species with bridging carbon and sulfur ligands that are high-spin with greater electronic and structural delity to the Fe2/Fe6 site are needed to improve the understanding of how biological S-and C-based donors impact N 2 reactivity.…”

Section: Introductionmentioning

confidence: 99%

The influences of carbon donor ligands on biomimetic multi-iron complexes for N₂reduction

et al. 2020

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“…In addition to materials applications, compounds in different spin state have vastly different reactivity, and this has implications in catalytic reactions both in biology and in synthetic chemistry. 1 Although initial observations of spin-crossover behavior were described by Cambi and co-workers as early as 1931, 2 it took more than 50 years before a more general understanding of the phenomenon was developed and its relevance more widely appreciated. 3 Despite the advances in the past decades, it is still not straightforward to rationally design spin-crossover compounds.…”

Section: Introductionmentioning

confidence: 99%

Electronic Control of Spin-Crossover Properties in Four-Coordinate Bis(formazanate) Iron(II) Complexes

et al. 2020

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The transition between spin states in d-block metal complexes has important ramifications for their structure and reactivity, with applications ranging from information storage materials to understanding catalytic activity of metalloenzymes. Tuning the ligand field (Δ O ) by steric and/or electronic effects has provided spin-crossover compounds for several transition metals in the periodic table, but this has mostly been limited to coordinatively saturated metal centers in octahedral ligand environments. Spin-crossover complexes with low coordination numbers are much rarer. Here we report a series of four-coordinate, (pseudo)tetrahedral Fe(II) complexes with formazanate ligands and demonstrate how electronic substituent effects can be used to modulate the thermally induced transition between S = 0 and S = 2 spin states in solution. All six compounds undergo spin-crossover in solution with T 1/2 above room temperature (300–368 K). While structural analysis by X-ray crystallography shows that the majority of these compounds are low-spin in the solid state (and remain unchanged upon heating), we find that packing effects can override this preference and give rise to either rigorously high-spin ( 6 ) or gradual spin-crossover behavior ( 5 ) also in the solid state. Density functional theory calculations are used to delineate the empirical trends in solution spin-crossover thermodynamics. In all cases, the stabilization of the low-spin state is due to the π-acceptor properties of the formazanate ligand, resulting in an “inverted” ligand field, with an approximate “two-over-three” splitting of the d-orbitals and a high degree of metal–ligand covalency due to metal → ligand π-backdonation. The computational data indicate that the electronic nature of the para -substituent has a different influence depending on whether it is present at the C–Ar or N–Ar rings, which is ascribed to the opposing effect on metal–ligand σ- and π-bonding.

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Two-state reactivity in C–H activation by a four-coordinate iron(0) complex

Cited by 31 publications

References 45 publications

Coupling dinitrogen and hydrocarbons through aryl migration

Coupling dinitrogen and hydrocarbons through aryl migration

The influences of carbon donor ligands on biomimetic multi-iron complexes for N₂reduction

Electronic Control of Spin-Crossover Properties in Four-Coordinate Bis(formazanate) Iron(II) Complexes

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Two-state reactivity in C–H activation by a four-coordinate iron(0) complex

Cited by 31 publications

References 45 publications

Coupling dinitrogen and hydrocarbons through aryl migration

Coupling dinitrogen and hydrocarbons through aryl migration

The influences of carbon donor ligands on biomimetic multi-iron complexes for N2reduction

Electronic Control of Spin-Crossover Properties in Four-Coordinate Bis(formazanate) Iron(II) Complexes

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The influences of carbon donor ligands on biomimetic multi-iron complexes for N₂reduction