Probing the role of an Fe<sup>IV</sup>tetrazene in catalytic aziridination

Cramer, S. Alan; Sánchez, Raúl Hernández; Brakhage, Desirae F.; Jenkins, David M.

doi:10.1039/c4cc05124f

Cited by 61 publications

(69 citation statements)

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“…[64] Reduction of am onomeric Fe IV is consistentw ith our previousr eported result with an iron(IV) tetrazene. [63] Characterizing 9 as Fe IV is also consistent with the diamagnetic (S = 0) 1…”

Section: Resultssupporting

confidence: 52%

“…[58][59][60][61][62] In contrast, for tetracarbene ligand platforms, we and others have shownt hat high oxidation states on iron are possible, with examples of isolatedm etallotetrazenes, imides,a nd oxos. [20,38,63] To help confirm the oxidation state on 9 we employed electrochemistry.C omparisons of the electrochemistry of molecules 6, 7 and 9 are shown below each crystal structure (Figures 2, 3a nd 5, bottom). For complex 6,t here is ar eversible trace at À0.98 Va nd an irreversible trace at À3.09 Vi nT HF versus the ferrocene/ferrocenium redox couple with (TBA)(PF 6 )a st he supporting electrolyte.…”

Section: Resultsmentioning

confidence: 99%

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A Chiral Macrocyclic Tetra‐N‐Heterocyclic Carbene Yields an “All Carbene” Iron Alkylidene Complex

DeJesus

Jenkins

2020

Chemistry A European J

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The first chiral macrocyclic tetra-N-heterocyclic carbene (NHC) ligand has been synthesized. The macrocycle, prepared in high yield andl arge scale,w as ligatedo ntop alladium and iron to give divalent C 2 -symmetric square planar complexes. Multinuclear NMR and single crystal X-ray diffraction demonstrated that there are two distinct NHCs on each ligand,d ue to the bridging chiral cyclohexane. Oxidationo f the iron(II) complex with trimethylamine N-oxide yielded a bridgingo xo complex.D iazodiphenylmethane reactedwith the iron(II) complex at room temperature to give ap aramag-netic diazoalkane complex;t he same reaction yieldedt he "all carbene" complexa te levated temperature. Electrochemical measurements support the assignment of the "all carbene"c omplex being an alkylidene. Notably,t he diazoalkane complex can be directly transformed into the alkylidene complex, which had not been previously demonstrated on iron. Finally,atest catalytic reactionw ithad iazoalkane on the iron(II) complex does not yield the expected cyclopropane,b ut actually the azine compound.[a] Dr.

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

A Chiral Macrocyclic Tetra‐N‐Heterocyclic Carbene Yields an “All Carbene” Iron Alkylidene Complex

DeJesus

Jenkins

2020

Chemistry A European J

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“…[33][34][35][36] Therefore, reports on mononuclear metal complexes with tetra-NHC ligands are limited to macrocyclic systems. [19][20][21][22][23][24][25][26][27][28][29]37 In addition, the accessible coordination modes for tetra-NHC ligands are limited, as they coordinate generally in an equatorial fashion, with the only exceptions being a tetrahedral Co II complex and a trigonal prismatic Fe IV tetrazene complex. 20,23 To overcome the structural rigidity that is responsible for this limitation, two open chain tetra-NHC ligands L1 and L2 with alkyl linkers of different lengths have been reported by our group together with the respective silver(I) complexes 1 and 2 (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The colorless mixture is heated to 85 °C for 5 d under vigorous stirring and then cooled to room temperature. After centrifuging under air, the colorless solution is separated from the colorless residue and precipitated under vigorous stirring by addition of20 mL diethyl ether. The colorless precipitate is washed with diethyl ether and dried under vacuum.…”

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Structural diversity of late transition metal complexes with flexible tetra-NHC ligands

et al. 2015

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The synthesis of copper, gold, nickel, palladium, platinum, and iron complexes with open chain tetra-N-heterocyclic carbene (NHC) ligands via transmetalation using silver NHC complexes is presented. The obtained complexes show differing coordination geometries depending on both ligand structure and metal. While the complexes of the coinage metals form di- or tetranuclear structures, the group 10 metal complexes exhibit a distorted square planar coordination geometry at the metal centers. In the case of iron an enhanced flexibility of the ligand - caused by a longer alkyl bridge - leads to octahedral complexes with a sawhorse-type coordination by the tetracarbene ligand and two cis acetonitrile ligands. To the best of our knowledge, this is the first known example of a tetracarbene ligand in sawhorse-type coordination within an octahedral coordination sphere. The remaining cis-labile sites are prone to exchange reactions as shown by addition of trimethylphosphine.

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“…[5] More recently, the family of iron-based catalysts has been expanded to include complexes that facilitate alkyl- and arylnitrene transfer to styrenes and aliphatic alkenes. [6] …”

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Styrene Aziridination by Iron(IV) Nitrides

et al. 2015

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Thermolysis of the iron(IV) nitride complex PhB(tBuIm)3Fe≡N with styrene leads to formation of the high spin iron(II) aziridino complex PhB(tBuIm)3Fe-N(CH2CHPh). Similar aziridination occurs with both electron-rich and electron-poor styrenes, while bulky styrenes hinder the reaction. The aziridino complex PhB(tBuIm)3Fe-N(CH2CHPh) acts as a nitride synthon, reacting with electron poor styrenes to generate their corresponding aziridino complexes, i.e. aziridine cross-metathesis. Reaction of PhB(tBuIm)3Fe-N(CH2CHPh) with Me3SiCl releases the N-functionalized aziridine Me3SiN(CH2CHPh) while simultaneously generating PhB(tBuIm)3FeCl. This closes a synthetic cycle for styrene azirdination by a nitride complex. While the less hindered iron(IV) nitride complex PhB(MesIm)3Fe≡N reacts with styrenes below room temperature, only bulky styrenes lead to tractable aziridino products.

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Probing the role of an Fe^IVtetrazene in catalytic aziridination

Abstract: An iron(IV) tetrazene complex has been synthesized that is an important addition to a previously proposed catalytic aziridination cycle. It provides two key insights about the aziridination: an iron(IV) imide is formed and this imide can bind an additional ligand in the cis position.

Cited by 61 publications

References 35 publications

A Chiral Macrocyclic Tetra‐N‐Heterocyclic Carbene Yields an “All Carbene” Iron Alkylidene Complex

A Chiral Macrocyclic Tetra‐N‐Heterocyclic Carbene Yields an “All Carbene” Iron Alkylidene Complex

Structural diversity of late transition metal complexes with flexible tetra-NHC ligands

Styrene Aziridination by Iron(IV) Nitrides

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Probing the role of an FeIVtetrazene in catalytic aziridination

Abstract: An iron(IV) tetrazene complex has been synthesized that is an important addition to a previously proposed catalytic aziridination cycle. It provides two key insights about the aziridination: an iron(IV) imide is formed and this imide can bind an additional ligand in the cis position.

Cited by 61 publications

References 35 publications

A Chiral Macrocyclic Tetra‐N‐Heterocyclic Carbene Yields an “All Carbene” Iron Alkylidene Complex

A Chiral Macrocyclic Tetra‐N‐Heterocyclic Carbene Yields an “All Carbene” Iron Alkylidene Complex

Structural diversity of late transition metal complexes with flexible tetra-NHC ligands

Styrene Aziridination by Iron(IV) Nitrides

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Probing the role of an Fe^IVtetrazene in catalytic aziridination