Synthesis of Bis(methoxycarbene) and Bis(alkylidene) Ligands Bridging Two Iron Centers in the Cp*Fe(L1)(L2) Series. X-ray Crystal Structure of the Iron Alkylidene [Cp*Fe(dppe)(C(H)Me)][PF<sub>6</sub>]

Mahias, Virginie; Cron, Stephane; Toupet, Loı̈c; Lapinte, Claude

doi:10.1021/om960454y

Cited by 62 publications

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“…Experimentally measured distances for 2- 6 ] 2 are given in parentheses. (2) ) bond lengths which compare well with those of iron-allenylidene derivatives, [8,35,36] are key geometric features consistent with a Fe=C bond order of about two and the presence of an almost positive charge on both iron centers. The central C42ÀC43 bond length is 1.349 (7) and the averaged adjacent CÀS bond length is 1.750 in the TTFMe 2 moieties.…”

Section: Cyclic Voltammetry Of 2a C H T U N G T R E N N U N G [Pf 6 ]supporting

confidence: 54%

Hybrid Molecular Systems Containing Tetrathiafulvalene and Iron‐Alkynyl Electrophores: Five‐Component Functional Molecules Obtained from CH Bond Activation

Justaud¹,

Gendron²,

Ogyu³

et al. 2013

Chemistry A European J

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Treatment of [Cp*(dppe)Fe-C≡C-TTFMe3] (1) with Ag[PF6] (3 equiv) in DMF provides the binuclear complex [Cp*(dppe)Fe=C=C=TTFMe2 =CH-CH=TTFMe2 =C=C=Fe(dppe)Cp*][PF6]2 (2[PF6 ]2) isolated as a deep-blue powder in 69 % yield. EPR monitoring of the reaction and comparison of the experimental and calculated EPR spectra allowed the identification of the radical salt [Cp*(dppe)Fe=C=C=TTFMe2 =CH][PF6]2 ([1-CH][PF6]) an intermediate of the reaction, which results from the activation of the methyl group attached in vicinal position with respect to the alkynyl-iron on the TTF ligand by the triple oxidation of 1 leading to its deprotonation by the solvent. The dimerization of [1-CH][PF6] through carbon-carbon bond formation provides 2[PF6]2. The cyclic voltammetry (CV) experiments show that 2[PF6]2 is subject to two sequential well-reversible one-electron reductions yielding the complexes 2[PF6] and 2. The CV also shows that further oxidation of 2[PF6]2 generates 2[PF6]n (n=3-6) at the electrode. Treatment of 2[PF6]2 with KOtBu provides 2[PF6] and 2 as stable powders. The salts 2[PF6] and 2[PF6]2 were characterized by XRD. The electronic structures of 2(n+) (n=0-2) were computed. The new complexes were also characterized by NMR, IR, Mössbauer, EPR, UV/Vis and NIR spectroscopies. The data show that the three complexes 2[PF6]n are iron(II) derivatives in the ground state. In the solid state, the dication 2(2+) is diamagnetic and has a bis(allenylidene-iron) structure with one positive charge on each iron building block. In solution, as a result of the thermal motion of the metal-carbon backbone, the triplet excited state becomes thermally accessible and equilibrium takes place between singlet and triplet states. In 2[PF6], the charge and the spin are both symmetrically distributed on the carbon bridge and only moderately on the iron and TTFMe2 electroactive centers.

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Section: Cyclic Voltammetry Of 2a C H T U N G T R E N N U N G [Pf 6 ]supporting

confidence: 54%

Hybrid Molecular Systems Containing Tetrathiafulvalene and Iron‐Alkynyl Electrophores: Five‐Component Functional Molecules Obtained from CH Bond Activation

Justaud¹,

Gendron²,

Ogyu³

et al. 2013

Chemistry A European J

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“…Moreover, metalloporphyrin dialkylcarbene species could be prone to undergo a 1,2-hydride shi, which is a common side reaction observed in dialkylcarbene transfer catalysis. 13 In addition, nonporphyrin group 8 metal dialkylcarbene complexes reported previously were oen prepared with a limited choice of ligand sets (e.g., phosphine, Cp, and tris(pyrazolyl)borate) and/or under demanding conditions (e.g., strong acid and reducing medium), [5][6][7][8] and only a few non-porphyrin 19 and Osdialkylcarbene 20 complexes have been structurally characterized by X-ray crystallographic studies and, despite the report of a structurally characterized Fe]CHMe non-porphyrin complex, 21 no crystal structure of an Fe-dialkylcarbene complex has been reported so far.…”

Section: Introductionmentioning

confidence: 99%

Stable group 8 metal porphyrin mono- and bis(dialkylcarbene) complexes: synthesis, characterization, and catalytic activity

et al. 2020

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Alkyl-substituted carbene (CHR or CR 2 , R ¼ alkyl) complexes have been extensively studied for alkylcarbene (CHR) ligands coordinated with high-valent early transition metal ions (a.k.a. Schrock carbenes or alkylidenes), yet dialkylcarbene (CR 2 ) complexes remain less developed with bis(dialkylcarbene) species being little (if at all) explored. Herein, several group 8 metal porphyrin dialkylcarbene complexes, including Fe-and Ru-mono(dialkylcarbene) complexes [M(Por)(Ad)] (1a,b, M ¼ Fe, Por ¼ porphyrinato dianion, Ad ¼ 2-adamantylidene; 2a,b, M ¼ Ru) and Os-bis(dialkylcarbene) complexes [Os(Por)(Ad) 2 ] (3ac), are synthesized and crystallographically characterized. Detailed investigations into their electronic structures reveal that these complexes are formally low-valent M(II)-carbene in nature. These complexes display remarkable thermal stability and chemical inertness, which are rationalized by a synergistic effect of strong metal-carbene covalency, hyperconjugation, and a rigid diamondoid carbene skeleton. Various spectroscopic techniques and DFT calculations suggest that the dialkylcarbene Ad ligand is unique compared to other common carbene ligands as it acts as both a potent s-donor and p-acceptor; its unique electronic and structural features, together with the steric effect of the porphyrin macrocycle, make its Fe porphyrin complex 1a an active and robust catalyst for intermolecular diarylcarbene transfer reactions including cyclopropanation (up to 90% yield) and X-H (X ¼ S, N, O, C) insertion (up to 99% yield) reactions. † Electronic supplementary information (ESI) available: Abbreviations, experimental procedures, characterization of compounds, computational details, Tables S1-S8, Fig. S1-S11, NMR spectra of compounds, Cartesian coordinates from DFT calculations, and CIF le for the crystal structure of 1b, 1a$Py, 2b$MeOH, 2az, and 3a. Scheme 1 Synthesis of Fe (a), Ru (b), and Os (c) dialkylcarbene complexes.This journal is a All values involving C1-3 are averaged between two Ad groups. b Average distances between M1 and pyrrolic nitrogens (N1-4). c L ax ¼ N5 (for 1a$Py) or O1 (for 2b$MeOH), or C1a (for 3a). View Article Online a E 1/2 values. 1a,b and 2a,b were measured in DMF with SCE as the reference electrode; E(Fc +/0 ) ¼ 0.49 V. 3a-c were measured in DCM with Ag/AgCl as the reference electrode; E(Fc +/0 ) ¼ 0.40 V. b E p,a . c E p,c . d Quasi-reversible. Scheme 4 Intermolecular diarylcarbene transfer reactions catalyzed by 1a. Product yields in red and recovery of 1a (blue) in parentheses. a Conditions: Ph 2 CN 2 (0.2 mmol), substrate (2 mmol), catalyst (0.004 mmol), DCM (1 mL), 40 C, 12 h, and under Ar. b Conditions: Ph 2 CN 2 (0.2 mmol, added over 3 h), substrate (2 mmol), catalyst (0.004 mmol), DCE (1 mL), 80 C, 12 h, and under Ar.Fig. 12 DFT-optimized structure of model complex 4b (left) and its LUMO (middle) and L + 3 orbitals (right).

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“…the carbene between 305 and 385 ppm, and are consistent with ad iamagnetic NMR. [52][53][54][55] Only examples by Floriani [56,57] and Chirik [45] have paramagnetic NMRs with this same diazoalkane fragment. As ingle crystal X-ray analysiso f9 showedt he first "all carbene" iron complex ( Figure 5).…”

Section: Resultsmentioning

confidence: 98%

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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Synthesis of Bis(methoxycarbene) and Bis(alkylidene) Ligands Bridging Two Iron Centers in the CpFe(L1)(L2) Series. X-ray Crystal Structure of the Iron Alkylidene [CpFe(dppe)(C(H)Me)][PF₆]

Cited by 62 publications

References 67 publications

Hybrid Molecular Systems Containing Tetrathiafulvalene and Iron‐Alkynyl Electrophores: Five‐Component Functional Molecules Obtained from CH Bond Activation

Hybrid Molecular Systems Containing Tetrathiafulvalene and Iron‐Alkynyl Electrophores: Five‐Component Functional Molecules Obtained from CH Bond Activation

Stable group 8 metal porphyrin mono- and bis(dialkylcarbene) complexes: synthesis, characterization, and catalytic activity

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

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Synthesis of Bis(methoxycarbene) and Bis(alkylidene) Ligands Bridging Two Iron Centers in the Cp*Fe(L1)(L2) Series. X-ray Crystal Structure of the Iron Alkylidene [Cp*Fe(dppe)(C(H)Me)][PF6]

Cited by 62 publications

References 67 publications

Hybrid Molecular Systems Containing Tetrathiafulvalene and Iron‐Alkynyl Electrophores: Five‐Component Functional Molecules Obtained from CH Bond Activation

Hybrid Molecular Systems Containing Tetrathiafulvalene and Iron‐Alkynyl Electrophores: Five‐Component Functional Molecules Obtained from CH Bond Activation

Stable group 8 metal porphyrin mono- and bis(dialkylcarbene) complexes: synthesis, characterization, and catalytic activity

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

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Synthesis of Bis(methoxycarbene) and Bis(alkylidene) Ligands Bridging Two Iron Centers in the CpFe(L1)(L2) Series. X-ray Crystal Structure of the Iron Alkylidene [CpFe(dppe)(C(H)Me)][PF₆]