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Highly Reactive Co^III,IV₂(?-O)₂ Diamond Core Complex That Cleaves C-H Bonds.

ABSTRACT: The selective activation of strong sp³ C-H bonds at mild conditions is a key step in many biological and synthetic transformations and an unsolved challenge for synthetic chemists. In nature, soluble methane monooxygenase (sMMO) is one representative example of nonheme dinuclear iron-dependent enzymes that activate strong sp³ C-H bonds by a high-valent diiron(IV) intermediate Q. To date, synthetic model complexes of sMMO-Q have shown limited abilities to oxidize strong C-H bonds. In this work, we generated a high-valent Co^III,IV₂(?-O)₂ complex 3 supported by a tetradentate tris(2-pyridylmethyl)amine (TPA) ligand via one-electron oxidation of its Co^III₂(?-O)₂ precursor 2. Characterization of 2 and 3 using X-ray absorption spectroscopy and DFT calculations showed that both species possess a diamond core structure with a short Co···Co distance of 2.78 Å. Furthermore, 3 is an EPR active species showing an S = 1/2 signal with clearly observable hyperfine splittings originated from the coupling of the ⁵⁹Co nuclear spin with the electronic spin. Importantly, 3 is a highly reactive oxidant for sp³ C-H bonds, and an oxygenation reagent. 3 has the highest rate constant (1.5 M^-1 s^-1 at -60 °C) for oxidizing 9,10-dihydroanthracene (DHA) compared to diamond core complexes of other first-row transition metals including Mn, Fe and Cu reported previously. Specifically, 3 is about 4-5 orders of magnitude more reactive than the diiron analogs Fe^III,IV₂(?-O)₂ and Fe^IV₂(?-O)₂ supported by TPA and related ligands. These findings shed light on future development of more reactive approaches for C-H bond activation by bioinspired dicobalt complexes.

SUBMITTER: Li Y

PROVIDER: S-EPMC6933091 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Highly Reactive CoIII,IV2(μ-O)2 Diamond Core Complex That Cleaves C-H Bonds.

Li Yan Y Handunneththige Suhashini S Farquhar Erik R ER Guo Yisong Y Talipov Marat R MR Li Feifei F Wang Dong D

Journal of the American Chemical Society 20191216 51

The selective activation of strong sp3 C-H bonds at mild conditions is a key step in many biological and synthetic transformations and an unsolved challenge for synthetic chemists. In nature, soluble methane monooxygenase (sMMO) is one representative example of nonheme dinuclear iron-dependent enzymes that activate strong sp3 C-H bonds by a high-valent diiron(IV) intermediate Q. To date, synthetic model complexes of sMMO-Q have shown limited abilities to oxidi ...[more]

PMID: 31794198

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Project description:The asymmetric unit of the title compound, [{Sn(C4H9)2(C6H5COO)}2O]2, consists of two half molecules, completed by application of inversion symmetry. Both mol-ecules adopt a ladder structure typical for this class of dimeric tetra-organodistannoxane di-carboxyl-ates characterized by a centrosymmetric four-membered (Sn-O)2 ring of rhomboidal shape that is extended on both sides by folded six-membered Sn-O-C rings. To a first approximation, both kinds of Sn atoms (Sn i and Sn o ) are trigonal-bipyramidally coordinated. The bond angles between the n-butyl groups are widened [135.64 (7)-146.20 (7)°] in comparison with an ideal trigonal bipyramid. Sn-O bond lengths within the {R2SnO3} coordination sphere depend strongly on the position of the corresponding O atom - axial (ax) or equatorial (eq) - as well as on the functionality of the carboxyl-ate groups which exhibit μ2 (-COO i ) and μ1 (-COO o ) coordination modes, respectively. In summary, the following sequence of distances [mean values] is found: d(Sn o -Oμ3) eq [2.024 (2) Å] < d(Sn i -Oμ3) eq [2.044 (2) Å] < d(Sn i -Oμ3) ax [2.158 (6) Å] < d(Sn o -Oμ1-carb) ax [2.182 (6) Å] < d(Sn i -Oμ2-carb) ax [2.250 (2) Å] ≃ d(Sn o -Oμ2-carb) ax [2.247 (12) Å]. The n-butyl groups adopt an anti-anti conformation with exception of two disordered outer n-butyl groups of the second mol-ecule which exhibit gauche-anti and anti-gauche conformations. Weak intra-molecular Sn⋯O inter-actions between the different O atoms of the outer carboxyl groups with the inner, as well as outer, Sn atoms give rise to a strongly distorted octa-hedral coordination at these Sn atoms. Inter-molecular inter-actions between the individual mol-ecules are restricted to van der Waals and O⋯H-C inter-actions of which a nearly linear very short C-H⋯O contact between the H atom of the phenyl group of one of the mol-ecules with the outer non-coordinating C=O group of the other molecule is the most prominent. It gives rise to a chain-like arrangement of the mol-ecules along [111]. The two n-butyl groups attached to the outer Sn atom of one mol-ecule are disordered over two sets of sites with occupancies of 0.806 (3)/0.194 (3) and 0.702 (3)/0.298 (3).

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Highly Reactive Co^III,IV₂(?-O)₂ Diamond Core Complex That Cleaves C-H Bonds.

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Highly Reactive Co<sup>III,IV</sup><sub>2</sub>(μ-O)<sub>2</sub> Diamond Core Complex That Cleaves C-H Bonds.

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Dataset Information

Highly Reactive CoIII,IV2(?-O)2 Diamond Core Complex That Cleaves C-H Bonds.

Publications

Highly Reactive Co<sup>III,IV</sup><sub>2</sub>(μ-O)<sub>2</sub> Diamond Core Complex That Cleaves C-H Bonds.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Highly Reactive Co^III,IV₂(?-O)₂ Diamond Core Complex That Cleaves C-H Bonds.