Aromatic hydroxylation by molecular oxygen performed by mononuclear benzoato iron(II) complexes and preparation of new iron(III) complex with two minus ligand

Using the tris(3,5-diphenylpyrazol-1-yl)borate (Ph2Tp) supporting ligand, a series of mono- and dinuclear ferrous complexes containing hydroquinonate (HQate) ligands have been prepared and structurally characterized with X-ray crystallography. The monoiron(II) complexes serve as faithful mimics of the substrate-bound form of hydroquinone dioxygenases (HQDOs) – a family of nonheme Fe enzymes that catalyze the oxidative cleavage of 1,4-dihydroxybenzene units. Reflecting the variety of HQDO substrates, the synthetic complexes feature both mono- and bidentate HQate ligands. The bidentate HQates cleanly provide five-coordinate, high-spin Fe(II) complexes with the general formula [Fe(Ph2Tp)(HLX)] (1X), where HLX is a HQate(1-) ligand substituted at the 2-position with a benzimidazolyl (1A), acetyl (1B and 1C), or methoxy (1D) group. In contrast, the monodentate ligand 2,6-dimethylhydroquinone (H2LF) exhibited a greater tendency to bridge between two Fe(II) centers, resulting in formation of [Fe2(Ph2Tp)2(μ-LF)(MeCN)] [2F(MeCN)]. However, addition of one equivalent of “free” pyrazole (Ph2pz) ligand provided the mononuclear complex, [Fe(Ph2Tp)(HLF)(Ph2pz)] [1F(Ph2pz)], which is stabilized by an intramolecular hydrogen bond between the HLF and Ph2pz donors. Complex 1F(Ph2pz) represents the first crystallographically-characterized example of a monoiron complex bound to an untethered HQate ligand. The geometric and electronic structures of the Fe/HQate complexes were further probed with spectroscopic (UV-vis absorption, 1H NMR) and electrochemical methods. Cyclic voltammograms of complexes in the 1X series revealed an Fe-based oxidation between 0 and −300 mV (vs. Fc+/0), in addition to irreversible oxidation(s) of the HQate ligand at higher potentials. The one-electron oxidized species (1Xox) were examined with UV-vis absorption and electron paramagnetic resonance (EPR) spectroscopies.

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“…21d, 22 The Fe1-O1 distances, which range between 1.927(1) and 1.961(1) Å, are also typical for iron(II)-phenolate units in 5C complexes. 23 …”

Section: Resultsmentioning

confidence: 99%

Structural, spectroscopic, and electrochemical properties of nonheme Fe(ii)–hydroquinonate complexes: synthetic models of hydroquinone dioxygenases

et al. 2012

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“…Consistent with tridentate scorpionate coordination, [53] ν(B-H) modes were observed at 2544-2547 cm -1 . [43][44][45][46][48][49][50][51] The ν(D-H) frequencies that arise from the D-H···A interactions correlate to the D···A separation for a wide range of donor-acceptor pairs. However, the adducts exhibit ν(B-H) modes at 2532-2536 cm -1 , downshifted from those of [(Tp Ph,Me )-Ni-X].…”

Section: Ftir Spectroscopymentioning

confidence: 99%

“…However, the adducts exhibit ν(B-H) modes at 2532-2536 cm -1 , downshifted from those of [(Tp Ph,Me )-Ni-X]. [43][44][45][46][48][49][50] (Table S2 in the Supporting Information). [43][44][45][46][48][49][50][51] The ν(D-H) frequencies that arise from the D-H···A interactions correlate to the D···A separation for a wide range of donor-acceptor pairs.…”

Section: Ftir Spectroscopymentioning

confidence: 99%

“…The adducts also display unique peaks at 3224 cm -1 (X = Cl), and 3218 and 3233 cm -1 (X = I), assigned to the N2-H···X hydrogen-bonding interaction (Table S2). [43][44][45][46][48][49][50] The data point represented by the open circle (᭺) [50] (RODHEX. [54,55] We find an empirically linear correlation (r 2 = 0.91) for pentacoordinate [(Tp 3R,5R )M(Hpz 3R,5R )(Cl)] complexes ( Figure 4 and Table S2 in the Supporting Information).…”

Section: Ftir Spectroscopymentioning

confidence: 99%

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Scorpionato Halide Complexes [(Tp^Ph,Me)Ni–X] [X = Cl, Br, I; Tp^Ph,Me = Hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate]: Structures, Spectroscopy, and Pyrazole Adducts

Deb

Anderson

et al. 2014

Eur J Inorg Chem

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Pseudotetrahedral scorpionato halide complexes [(Tp Ph,Me ) Ni-X] [Tp Ph,Me = hydrotris(3-phenyl-5-methyl-1-pyrazolyl) borate] were synthesized by metathesis of Tl(Tp Ph,Me ) and NiX 2 (X = Cl, Br, I). Pyrazole adducts [(Tp Ph,Me )Ni(Hpz Ph,Me ) (X)] (X = Cl, I) were also obtained. [(Tp Ph,Me )Ni-X] (X = Br, I) are isomorphous with previously reported [(Tp Ph,Me )Ni-Cl], and a new solvated pseudo-polymorph [(Tp Ph,Me )Ni-Cl]·2CH 2 Cl 2 was found in this work.Ni-X bond lengths correspond to ionic radii of the halide ions, but some variations in Ni-Cl and Ni-N bond lengths are respectively attributed to bending of the chloride from the ideal threefold HB···Ni axis and to the size of the 3-pyrazole substituents.

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“…[24] The N and O atoms in the 3·2CH 2 Cl 2 structure were renumbered to correspond to the numbering scheme used for the other complexes. [24] The N and O atoms in the 3·2CH 2 Cl 2 structure were renumbered to correspond to the numbering scheme used for the other complexes.…”

Section: Fe 2+ Complexes Containing 2-tip Ph2mentioning

confidence: 99%

Synthesis and Structural Characterization of Iron(II) Complexes with Tris(imidazolyl)phosphane Ligands: A Platform for Modeling the 3‐Histidine Facial Triad of Nonheme Iron Dioxygenases

et al. 2012

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Several monoiron(II) complexes containing tris(imidazolyl)phosphane (TIP) ligands have been prepared and structurally characterized by using X-ray crystallography and NMR spectroscopy. Two TIP ligands were employed: tris(2-phenylimidazol-4-yl)phosphane (4-TIP Ph ) and tris(4,5-diphenyl-1methylimidazol-2-yl)phosphane (2-TIP Ph2 ). These tridentate ligands resemble the 3-histidine (3His) facial triad found recently in the active sites of certain nonheme iron dioxygenases. Three of the reported complexes are designed to serve [a]

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Aromatic hydroxylation by molecular oxygen performed by mononuclear benzoato iron(II) complexes and preparation of new iron(III) complex with two minus ligand

Cited by 8 publications

References 14 publications

Structural, spectroscopic, and electrochemical properties of nonheme Fe(ii)–hydroquinonate complexes: synthetic models of hydroquinone dioxygenases

Structural, spectroscopic, and electrochemical properties of nonheme Fe(ii)–hydroquinonate complexes: synthetic models of hydroquinone dioxygenases

Scorpionato Halide Complexes [(Tp^Ph,Me)Ni–X] [X = Cl, Br, I; Tp^Ph,Me = Hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate]: Structures, Spectroscopy, and Pyrazole Adducts

Synthesis and Structural Characterization of Iron(II) Complexes with Tris(imidazolyl)phosphane Ligands: A Platform for Modeling the 3‐Histidine Facial Triad of Nonheme Iron Dioxygenases

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Aromatic hydroxylation by molecular oxygen performed by mononuclear benzoato iron(II) complexes and preparation of new iron(III) complex with two minus ligand

Cited by 8 publications

References 14 publications

Structural, spectroscopic, and electrochemical properties of nonheme Fe(ii)–hydroquinonate complexes: synthetic models of hydroquinone dioxygenases

Structural, spectroscopic, and electrochemical properties of nonheme Fe(ii)–hydroquinonate complexes: synthetic models of hydroquinone dioxygenases

Scorpionato Halide Complexes [(TpPh,Me)Ni–X] [X = Cl, Br, I; TpPh,Me = Hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate]: Structures, Spectroscopy, and Pyrazole Adducts

Synthesis and Structural Characterization of Iron(II) Complexes with Tris(imidazolyl)phosphane Ligands: A Platform for Modeling the 3‐Histidine Facial Triad of Nonheme Iron Dioxygenases

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Scorpionato Halide Complexes [(Tp^Ph,Me)Ni–X] [X = Cl, Br, I; Tp^Ph,Me = Hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate]: Structures, Spectroscopy, and Pyrazole Adducts