Nickel(II) and Iron(II) Complexes with Tetradentate NHC/Amide Hybrid Ligands

Klawitter, Iris; Meyer, S.; Demeshko, Serhiy; Meyer, Franc

doi:10.5560/znb.2013-3091

Cited by 12 publications

(7 citation statements)

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“…327 The formation of 158 Nickel NHC complexes are mostly known for the oxidation states II, I, and 0. While high-oxidation-state nickel NHC species were thought to be involved in the electrochemical oxidation of nickel(II) NHC species 328 as well as nickel− NHC-catalyzed reactions, 329−331 the reported examples of isolable high-oxidation-state nickel complexes with NHC ligation are limited to Fout's nickel(IV) halide complexes, which are supported by the NHC−aryl−NHC pincer ligand [ Dipp CCC-2]. 141 Fout's study on ( Ar CCC-2)cobalt complexes revealed the ability of the electron-rich bis(NHC)−aryl pincer ligand to support d 6 cobalt(III) species.…”

Section: Complexes Of Cobaltmentioning

confidence: 99%

“…Meyer et al proposed the formation of a nickel(III) species bearing tetradentate bis(NHC)-bis(amide) ligands, of the form [(C 2 N 2 )Ni] + ( 163 in Chart ), in the electrochemical oxidation of its nickel(II) precursor . Cyclic voltammetry in aqueous solution revealed a half-wave potential of +0.89 V (versus NHE) for the quasi-reversible one-electron redox process of [(C 2 N 2 )Ni] 0/1+ .…”

Section: High-oxidation-state 3d Metal Complexes With Nhc Ligationmentioning

confidence: 99%

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High-Oxidation-State 3d Metal (Ti–Cu) Complexes withN-Heterocyclic Carbene Ligation

et al. 2018

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High-oxidation-state 3d metal species have found a wide range of applications in modern synthetic chemistry and materials science. They are also implicated as key reactive species in biological reactions. These applications have thus prompted explorations of their formation, structure, and properties. While the traditional wisdom regarding these species was gained mainly from complexes supported by nitrogen- and oxygen-donor ligands, recent studies with N-heterocyclic carbenes (NHCs), which are widely used for the preparation of low-oxidation-state transition metal complexes in organometallic chemistry, have led to the preparation of a large variety of isolable high-oxidation-state 3d metal complexes with NHC ligation. Since the first report in this area in the 1990s, isolable complexes of this type have been reported for titanium(IV), vanadium(IV,V), chromium(IV,V), manganese(IV,V), iron(III,IV,V), cobalt(III,IV,V), nickel(IV), and copper(II). With the aim of providing an overview of this intriguing field, this Review summarizes our current understanding of the synthetic methods, structure and spectroscopic features, reactivity, and catalytic applications of high-oxidation-state 3d metal NHC complexes of titanium to copper. In addition to this progress, factors affecting the stability and reactivity of high-oxidation-state 3d metal NHC species are also presented, as well as perspectives on future efforts.

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Section: Complexes Of Cobaltmentioning

confidence: 99%

Section: High-oxidation-state 3d Metal Complexes With Nhc Ligationmentioning

confidence: 99%

High-Oxidation-State 3d Metal (Ti–Cu) Complexes withN-Heterocyclic Carbene Ligation

et al. 2018

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“…While first examples of Fe–NHC complexes were introduced during the 1970s, , the first molecular structure was published in 1996 . Fe–NHC complexes have received much attention in recent years because of their great potential in catalysis , and in bioinspired chemistry , as well as for the stabilization of reactive intermediates and unusual iron oxidation states. − A common method for synthesizing iron(II)–NHC complexes is the reaction of the respective imidazolium salts with the basic iron(II) precursor [Fe{N(SiMe 3 ) 2 } 2 ] 2 . − …”

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Iron Complexes of a Macrocyclic N-Heterocyclic Carbene/Pyridine Hybrid Ligand

et al. 2015

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The tetradentate ligand system L 1 combines two Nheterocyclic carbene (NHC) and two pyridine donor functions in a macrocyclic scaffold. Its iron(II) complex [FeL 1 (MeCN) 2 ](PF 6 ) 2 (1) has been synthesized and fully characterized. The macrocyclic ligand in 1 is puckered and shows a significant barrier for ring inversion (ΔH ⧧ = 15.1 kcal mol −1 , and ΔS ⧧ = −4.7 cal mol −1 K −1 ). Axial ligands in 1 can be readily substituted to give heteroleptic [FeL 1 (CO)(MeCN)](PF 6 ) 2 (2) or neutral [FeL 1 (N 3 ) 2 ] (3). The strong ligand field of the NHC/pyridine hybrid ligand imparts low-spin states (S = 0) for all iron(II) complexes 1−3. Mossbauer data reflect the asymmetric electronic situation that results from the strongly covalent Fe−C NHC bonds in the basal plane constituted by the macrocyclic ligand L 1 . Oxidation of 1 has been monitored by UV−vis spectro-electro chemistry, and the resulting iron(III) complex [FeL 1 (MeCN) 2 ](PF 6 ) 3 (4) has been isolated after chemical oxidation. SQUID and Mossbauer data have shown an S = 1 / 2 ground state for 4, and X-ray crystallographic analyses of 1 and 4 revealed that structural parameters of the {FeL 1 } core are basically invariant with respect to changes in the metal ion's oxidation state. Density functional theory calculations support the experimental findings. The combined structural, spectroscopic, and electrochemical data for 1 with its {C 2 N 2 } hybrid ligand L 1 allowed for useful comparison with the related iron(II) complex that has a macrocyclic {C 4 } tetracarbene ligand. N-Heterocyclic carbenes (NHCs) have attracted a great deal of attention over the past two decades. NHCs, most of them imidazol-2-ylidenes, are now established as a prime ligand class in organometallic chemistry, with numerous applications in homogeneous catalysis.

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“…In addition, according to previous studies, the tetradentate NHC ligand-coordinated nonprecious d 6 metal complex tends to adopt a non-coplanar geometry. 49–53…”

Section: Resultsmentioning

confidence: 99%

Disarming the alkoxide trap to access a practical FeCl₃ system for borrowing-hydrogen N-alkylation

Yang

et al. 2022

Org. Chem. Front.

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Nickel(II) and Iron(II) Complexes with Tetradentate NHC/Amide Hybrid Ligands

Cited by 12 publications

References 30 publications

High-Oxidation-State 3d Metal (Ti–Cu) Complexes withN-Heterocyclic Carbene Ligation

High-Oxidation-State 3d Metal (Ti–Cu) Complexes withN-Heterocyclic Carbene Ligation

Iron Complexes of a Macrocyclic N-Heterocyclic Carbene/Pyridine Hybrid Ligand

Disarming the alkoxide trap to access a practical FeCl₃ system for borrowing-hydrogen N-alkylation

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Nickel(II) and Iron(II) Complexes with Tetradentate NHC/Amide Hybrid Ligands

Cited by 12 publications

References 30 publications

High-Oxidation-State 3d Metal (Ti–Cu) Complexes withN-Heterocyclic Carbene Ligation

High-Oxidation-State 3d Metal (Ti–Cu) Complexes withN-Heterocyclic Carbene Ligation

Iron Complexes of a Macrocyclic N-Heterocyclic Carbene/Pyridine Hybrid Ligand

Disarming the alkoxide trap to access a practical FeCl3 system for borrowing-hydrogen N-alkylation

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Disarming the alkoxide trap to access a practical FeCl₃ system for borrowing-hydrogen N-alkylation