A DFT overview of high-valent iron, cobalt and nickel tetraamidomacrocyclic ligand (TAML) complexes: The end of innocence?

Conradie, Marrigje M.; Conradie, Jeanet; Ghosh, Abhik

doi:10.1016/j.jinorgbio.2006.01.028

Cited by 16 publications

(16 citation statements)

References 41 publications

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“…14b, 27 The main edge feature arises primarily from 1s → 4p electron transitions, whereas the feature at 7715 eV is commonly assigned to 1s → 4pz and ligand to metal charge transfer (LMCT) shakedown transitions. 37 In agreement with previous studies, 27,29 DFT calculations with various GGA and hybrid functionals (BP86, B3LYP, PBE and OPBE; see SI for details) gave unsatisfactory results for the Co(TAML)-type complexes under investigation. An illustrative example of the problem encountered with DFT is found in the challenging description of the net-doublet ground state of the [Co III (TAML sq )] complex.…”

Section: Scheme 2 (A)supporting

confidence: 84%

“…This data was interpreted in 1998 as corresponding to an S = 1 cobalt(III) center antiferromagnetically coupled to a ligand-centered radical ([Co III (TAM-L sq )]). 28 Ghosh et al 29 reported an elaborate density functional theory (DFT) study on the ligand non-innocence of multiple variations of the TAML backbone, and suggested that the electronic structure of [Co III (TAML sq )] is better described as [Co IV (TAML red )] (Figure 1). Their assignment was based on the Mulliken spin density, which was solely localized on cobalt.…”

Section: Introductionmentioning

confidence: 99%

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Ligand Redox Non-Innocence in [Coᴵᴵᴵ(TAML)]0/‒ Complexes Affects Nitrene Formation

Leest¹,

Tepaske²,

Oudsen³

et al. 2019

Preprint

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The redox non-innocence of the TAML scaffold in cobalt-TAML (Tetra-Amido Macrocyclic Ligand) complexes has been under debate since 2006. In this work we demonstrate with a variety of spectroscopic measurements that the TAML backbone in the anionic complex [CoIII(TAMLred)]- is truly redox non-innocent, and that one-electron oxidation affords [CoIII(TAMLsq)]. Multi-reference (CASSCF) calculations show that the electronic structure of [CoIII(TAMLsq)] is best described as an intermediate spin (S = 1) cobalt(III) center that is antiferromagnetically coupled to a ligand-centered radical, affording an overall doublet (S = ½) ground-state. Reaction of the cobalt(III)-TAML complexes with PhINNs as a nitrene precursor leads to TAML-centered oxidation, and produces nitrene radical complexes without oxidation of the metal ion. The ligand redox state (TAMLred or TAMLsq) determines whether mono- or bis-nitrene radical complexes are formed. Reaction of [CoIII(TAMLsq)] or [CoIII(TAMLred)]- with PhINNs results in formation of [CoIII(TAMLq)(N•Ns)] and [CoIII(TAMLq)(N•Ns)2]-, respectively. Herein, ligand-to-substrate single-electron transfer results in one-electron reduced Fischer-type nitrene radicals (N•Ns-) that are intermediates in catalytic nitrene transfer to styrene. These nitrene radical species were characterized by EPR, XANES, and UV-Vis spectroscopy, high resolution mass spectrometry, magnetic moment measurements and supporting CASSCF calculations.

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Section: Scheme 2 (A)supporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Ligand Redox Non-Innocence in [Coᴵᴵᴵ(TAML)]0/‒ Complexes Affects Nitrene Formation

Leest¹,

Tepaske²,

Oudsen³

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Relative energies of these electron distribution and spin alternatives are currently best done by computational methods. [70,71] The recent appearance of a phosphorus analog of BIMPY suggests that new developments with this C 5 NH 3 (CH=PAr) 2 analog will appear. [72] Heterodienes incorporating two phosphorus (instead of nitrogen) show electrochemical reduction potentials less negative than those of their nitrogen analogs: bipy vs. the P analogs.…”

Section: Discussionmentioning

confidence: 99%

Systematics and Future Projections Concerning Redox‐Noninnocent Amide/Imine Ligands

Caulton

2011

Eur J Inorg Chem

119

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An analysis of the conjugative possibilities of dienes carrying two terminal heteroatom donors shows some generalizations of these as possible redox‐active (redox “noninnocent”) ligands. If the two E=C functionalities (E = O,S, NR, CHR) are connected by an odd number of sp2‐hybridized atoms, full conjugation between the two terminal E donors is not possible, a situation which is found both in 2,6‐bis(imino)pyridine (BIMPY) and beta‐diketiminate ligands; the character of their redox noninnocence is thus altered, compared to 1,4‐diheterodienes. Some insight into the BIMPY ligand comes from the analog where one imino arm is absent. The traditional stereochemical relationships which govern conjugation in arenes are analyzed for their implications for different bis(imino)pyridine isomers, and also for 2,6‐dipyrimidyl‐ and dipyridazinyl‐pyridines, as generalizations of the classic terpyridyl ligands. Factors which favor oxidized vs. reduced ligand forms are discussed.

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“…[27] A number of biomimetic polydentate non-heme ligands, such as 1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane (TMC) [28,29] and N,N-bis (2-pyridylmethyl)-N-bis(2-pyridyl)methylamine (N4Py), [30] capable of stabilising high-valent iron states have been synthesised and extensively studied since 2000. [31,32] Various ferryl complexes with room-temperature lifetimes that range from seconds to days have been generated and identified spectroscopically and, to date, three of them have been characterised crystallographically. [29,31,33,34] An important issue is the presence and role of different spin states of oxidoiron complexes.…”

Section: Introductionmentioning

confidence: 99%

The Role of Equatorial and Axial Ligands in Promoting the Activity of Non‐Heme Oxidoiron(IV) Catalysts in Alkane Hydroxylation

2007

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Keywords: Density functional calculations / Fenton reaction / Alkanes / Hydroxylation / High-valent oxidoiron(IV) systems / Push effectThe key electronic structural feature of the FeO 2+ moiety, which determines its activity as an alkane hydroxylation catalyst, is the presence of low-lying acceptor orbitals, namely the 3σ* 3d z 2-2p z antibonding orbital. Both the energetic position of this orbital and the spin state of the system (which in turn also affects the 3σ* energy) depend on the surrounding ligands. We present results of density functional theory (DFT) calculations performed on a series of gas-phase complexes of2+ by substitution of ligand water molecules with L = NH 3 , CH 3 CN, H 2 S and BF 3 . The calculations reveal that the high-spin (quintet) state is favoured by the weaker σ-donating equatorial ligands, which is consistent with the literature. The high-spin configuration is more reactive because of significant exchange stabilisation of the crucial 3σ*Ȇ orbital. Once the

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A DFT overview of high-valent iron, cobalt and nickel tetraamidomacrocyclic ligand (TAML) complexes: The end of innocence?

Cited by 16 publications

References 41 publications

Ligand Redox Non-Innocence in [Coᴵᴵᴵ(TAML)]0/‒ Complexes Affects Nitrene Formation

Ligand Redox Non-Innocence in [Coᴵᴵᴵ(TAML)]0/‒ Complexes Affects Nitrene Formation

Systematics and Future Projections Concerning Redox‐Noninnocent Amide/Imine Ligands

The Role of Equatorial and Axial Ligands in Promoting the Activity of Non‐Heme Oxidoiron(IV) Catalysts in Alkane Hydroxylation

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