An Exclusively Organometallic {FeNO}7 Complex with Tetracarbene Ligation and a Linear FeNO Unit

Küpper, Claudia; Schober, Anne; Demeshko, Serhiy; Bergner, Marie; Meyer, Franc

doi:10.1021/acs.inorgchem.5b00301

Cited by 30 publications

(76 citation statements)

References 27 publications

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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%

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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Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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“…Iron complexes supported by macrocyclic tetracarbene ligand scaffolds have been intensively studied in recent years, but the focus has been on their use in oxidation/oxygenation [31][32][33][34][35][36] and aziridination chemistry [37][38][39] as well as the isolation of high-valent and biorelevant reactive intermediates. [40][41][42][43][44] In contrast, the reductive chemistry of such "organometallic heme analogues" 35,45 has hardly been studied so far. Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

Selective Electrocatalytic CO₂ Reduction to CO by an NHC-Based Organometallic Heme Analogue

et al. 2021

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Molecular first-row transition metal complexes for electrocatalytic CO2 reduction mostly feature N-donor supporting ligands, iron porphyrins being among the most prominent catalysts. Introducing N-heterocyclic carbene (NHC) ligation has previously shown promising effects for some systems, yet the application of NHC iron complexes for electrochemical CO2 reduction has so far remained unreported. Herein we show that the macrocyclic tetracarbene iron complex [LFe(NCMe)2](OTf)2 (1), which can be described as an organometallic heme analogue, mediates selective electrocatalytic CO2to-CO conversion with a faradaic efficiency of over 90% and a very high initial observed catalytic rate constant (kobs) of 7,800 s −1 . Replacement of an axial MeCN ligand by CO significantly increases the catalyst stability and turnover number, while the rate of catalysis decreases only slightly (kobs = 3,100 s −1 ). Ferrous complexes with one or two axial CO ligands, [LFe(NCMe)(CO)](OTf)2 (1-CO) and [LFe(CO)2](OTf)2 (1-(CO)2), have been isolated and fully characterized. Based on linear sweep voltammogram (LSV) spectroelectro-IR (SEC-IR) studies for 1 and 1-CO, both under N2 and CO2 atmosphere, a mechanistic scenario in anhydrous acetonitrile is proposed. It involves two molecules of CO2 and results in CO and CO3 2− formation, whereby the first CO2 binds to the doubly reduced, pentacoordinated [LFe 0 (CO)] species. This work commences the exploration of the reductive chemistry by the widely tunable macrocyclic tetracarbene iron motif, which is topologically similar to hemes but electronically distinct as the strongly -donating and redox inactive NHC scaffold leads to metal-centered reduction and population of the exposed dz² orbital, in contrast to ligand-based orbitals in the analogous porphyrin systems.

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Section: Introductionmentioning

confidence: 99%

Selective Electrocatalytic CO2 Reduction to CO by an NHC-Based Organometallic Heme Analogue

Massie¹,

Schremmer²,

Rüter³

et al. 2020

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Molecular first-row transition metal complexes for electrocatalytic CO2 reduction mostly feature N-donor supporting ligands, iron porphyrins being among the most prominent catalysts. Introducing N-heterocyclic carbene (NHC) ligation has previously shown promising effects for some systems, yet the application of NHC iron complexes for electrochemical CO2 reduction has so far remained unreported. Herein we show that the macrocyclic tetracarbene iron complex [LFe(NCMe)2](OTf)2 (1), which can be described as an organometallic heme analogue, mediates selective electrocatalytic CO2-to-CO conversion with a faradaic efficiency of over 90% and a very high initial observed catalytic rate constant (kobs) of 7,800 s−1. Replacement of an axial MeCN ligand by CO significantly increases the catalyst stability and turnover number, while the rate of catalysis decreases only slightly (kobs = 3,100 s−1). Ferrous complexes with one or two axial CO ligands, [LFe(NCMe)(CO)](OTf)2 (1-CO) and [LFe(CO)2](OTf)2 (1-(CO)2), have been isolated and fully characterized. Based on linear sweep voltammogram (LSV) spectroelectro-IR (SEC-IR) studies for 1 and 1-CO, both under N2 and CO2 atmosphere, a mechanistic scenario in anhydrous acetonitrile is proposed. It involves two molecules of CO2 and results in CO and CO32− formation, whereby the first CO2 binds to the doubly reduced, pentacoordinated [LFe0(CO)] species. This work commences the exploration of the reductive chemistry by the widely tunable macrocyclic tetracarbene iron motif, which is topologically similar to hemes but electronically distinct as the strongly s-donating and redox inactive NHC scaffold leads to metal-centered reduction and population of the exposed dz² orbital, in contrast to ligand-based orbitals in the analogous porphyrin systems.

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An Exclusively Organometallic {FeNO}⁷ Complex with Tetracarbene Ligation and a Linear FeNO Unit

Cited by 30 publications

References 27 publications

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

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

Selective Electrocatalytic CO₂ Reduction to CO by an NHC-Based Organometallic Heme Analogue

Selective Electrocatalytic CO2 Reduction to CO by an NHC-Based Organometallic Heme Analogue

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