Oxygenation of Hydrocarbons Mediated by Mixed-Valent Basic Iron Trifluoroacetate and Valence-Separated Component Species under Gif-Type Conditions Involves Carbon- and Oxygen-Centered Radicals

Tapper, Amy E.; Staples, Richard J.; Stavropoulos, Pericles

doi:10.1002/1521-3773(20000703)39:13<2343::aid-anie2343>3.0.co;2-t

Cited by 38 publications

(5 citation statements)

References 20 publications

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“…Reduction of [Fe 3 O(O 2 CCMe 3 ) 6 (py) 3 ]Cl ( 2 ) or [Fe 3 O(O 2 CCMe 3 ) 6 (py) 3 ] by excess Zn dust in pyridine generates yellow-green solutions from which the air-sensitive [Fe II (O 2 CCMe 3 ) 2 (py) 4 ] ( 3 ) is isolated in good yields. Compound 3 , which can also be prepared pure by stirring Fe powder with 2 equiv of PivH in pyridine under reflux, reveals a structure (Supporting Information) which has now been documented in our laboratory for a number of other trans -[Fe II (O 2 CCR 3 ) 2 (py) 4 ] (R = H, F) complexes. ,6c The solid-state structure is retained in solution (py, CH 2 Cl 2 ) as indicated by 1 H NMR data, although in non-pyridine solvents the compound becomes exceedingly air sensitive, suggesting that small amounts of the known five-coordinate species [Fe II 2 (O 2 CCMe 3 ) 4 (py) 2 ] may be present in equilibrium.…”

Section: Resultsmentioning

confidence: 80%

Synthesis, Characterization, and Reactivity of Ferrous and Ferric Oxo/Peroxo Pivalate Complexes in Relation to Gif-Type Oxygenation of Substrates

2000

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This study examines structural features and aspects of reactivity of Gif-type reagents, which depend on O2/Zn to mediate oxidation of hydrocarbons. The reagents investigated derive from the use of iron complexes with the anion of the weak carboxylic acid Me3CCO2H (pivalic acid (PivH)) in pyridine/PivH. In these solutions, the known compound [Fe3O(O2CCMe3)6(py)3] is reduced by Zn to generate yellow-green [FeII(O2CCMe3)2(py)4], which readily reverts to [Fe3O(O2CCMe3)6(py)3], and eventually to [Fe3O(O2CCMe3)6(py)3]+, upon exposure to dioxygen. All three species are equally well suited to mediate Gif-like oxygenation of substrates supported by O2/Zn. [FeIII3O(O2CCMe3)6(L)3]+ (L = H2O, py) is converted by H2O2 to afford the hexairon(III) peroxo compounds [Fe6(O2)(O)2(O2CCMe3)12(L)2] (L = Me3CCO2H, py), which feature a [Fe6(eta 2-mu 4-O2)(mu 3-O)2] core previously documented in the closely related [Fe6(O2)(O)2(O2CPh)12(H2O)2]. A similar peroxo species, [Fe6(O2)(O)2(O2CCMe3)2(O2CCF3)10(H2O)2], is obtained upon replacing all pivalate ligands by trifluoroacetate groups with the exception of those pivalates that bridge between the two [Fe3O(O2CCF3)5(H2O)]2+ units. The structure of the [Fe6(O2)(O)2] core in these peroxo species is found to range from a recliner to a butterfly-type conformation. Reduction of [Fe6(O2)(O)2(O2CCMe3)12(HO2CCMe3)2] with NaBH4 generates [Na2Fe4(O)2(O2CCMe3)10(L)(L')] (L = CH3CN, L' = Me2CO; L = L' = Me3CCO2H), which feature a [Na2Fe4(O)2] core possessing a bent butterfly conformation of the [Fe4(O)2] unit. Oxidation of the same peroxo complex by CeIV or NOBF4 regenerates the oxo-bridged [Fe3O(O2CCMe3)6(solv)3]+ (solv = EtOH, H2O, thf). Employment of the sterically encumbered 2-Me-5-Etpyridine provides the tetrairon compound [Fe4(O)2(O2CCMe3)8(2-Me-5-Etpy)2], which can be readily transformed upon treatment with H2O2 to the asymmetric peroxo complex [Fe6(O2)(O)2(O2CCMe3)12(2-Me-5-Etpy)2]. The peroxo-containing complexes oxidize both cis-stilbene and adamantane in either benzene or py/PivH, but only under forceful conditions and at very low yields. The low reactivity and high selectivity (tert/sec = 8) obtained in the oxidation of adamantane suggests that the present type of peroxo species is not directly involved in catalytic Gif-type oxygenations of adamantane.

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Section: Resultsmentioning

confidence: 80%

Synthesis, Characterization, and Reactivity of Ferrous and Ferric Oxo/Peroxo Pivalate Complexes in Relation to Gif-Type Oxygenation of Substrates

2000

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“…Transition metal polynuclear carboxylate complexes are currently widely investigated, especially, for the following important reasons: (i) besides 1D, 2D, or 3D magnetic ordering which takes place in carboxylate containing compounds, it has been found that even individual molecules of such complexes could behave as individual magnets at low temperature, the so-called Single-Molecule Magnets (SMM); (ii) theses complexes are also successfully used as biomimetic models of some polymetallic active centers of enzymes; (iii) these polynuclear complexes can be viewed as extended models of intermediates during the geosediments formation; (iv) these compounds can efficiently catalyze different unique organic reactions due to the ability of polymetallic centers to coordinate and to activate several functional groups of a substrate; (v) recently, it has been demonstrated that some polynuclear carboxylate complexes can be used as precursors for synthesis of nanosized magnetic oxides . Hence, the development of a new strategy for synthesis of polynuclear skeletons which can lead to a wide variety of unknown topologies of polynuclear framework is still an actual challenge in modern coordination chemistry.…”

Section: Introductionmentioning

confidence: 99%

In Situ Generation of Carboxylate: An Efficient Strategy for a One-Pot Synthesis of Homo- and Heterometallic Polynuclear Complexes

et al. 2005

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An efficient strategy for synthesis of a wide range of homo- and heterometallic polynuclear complexes is proposed. The synthesis protocol consists of a two-step one-pot reaction. The first step is the in situ generation of carboxylate anions via oxidation of aromatic aldehydes by metal nitrates in air. The aldehydes act as solvents and are also involved in redox processes. Solutions containing solely transition metal cations and aromatic carboxylates are obtained following this procedure. The second step is a tunable "à la carte" formation of a series of various polynuclear carboxylato complexes from solutions obtained at the former stage upon addition of different solvents. The polarity and donor properties of the solvents play a key role in determination of the nuclearities of the complexes. Hydrolytic processes can induce the formation of oxo- or hydroxo-bridges inside the polynuclear core as well. Complexes of various nuclearities are obtained: from discrete tri-, hexa-, or octanuclear units to 1D polymers. This protocol can be adapted with disconcerting simplicity to the synthesis of heterometallic species with similar molecular structures to their homometallic analogues starting from stoichiometric mixture of metal nitrates under the same reaction conditions. Detailed description of synthesis and the molecular structure of one representative complex for each series are presented in this paper. The temperature dependence of magnetic susceptibility of the heterometallic 1-D MnCo chain reveals typical behavior of a ferrimagnetic chain. The low-temperature investigations on single crystals show significant Ising type magnetic anisotropy.

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“…For instance, the generation of 2-methylpyridine has been shown to be a byproduct of the oxidation of DMSO/EtOH by H 2 O 2 mediated by [Fe II (O 2 CCF 3 ) 2 (py) 4 ] in pyridine(py)/trifluoroacetic acid (TFA) under argon, via the formation of pyridine-trapped alkyl radicals. [12] This same group has also previously reported a similar type of reaction, although in this case, the production of 2-methylpyridine was mediated by [Fe II (Pic) 2 (py) 4 ], a picolinic acid (Pic)-derived catalyst in the presence of DMSO and DMSO/EtOH. [13] All of these reactions proceed via the production of alkyl radicals that add to every position in pyridine, generating 2, 3 and 4-methylpyridines.…”

Section: Introductionmentioning

confidence: 77%

Flow Synthesis of 2-Methylpyridines via α-Methylation

Manansala

Tranmer

2015

Molecules

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A series of simple 2-methylpyridines were synthesized in an expedited and convenient manner using a simplified bench-top continuous flow setup. The reactions proceeded with a high degree of selectivity, producing α-methylated pyridines in a much greener fashion than is possible using conventional batch reaction protocols. Eight 2-methylated pyridines were produced by progressing starting material through a column packed with Raney ® nickel using a low boiling point alcohol (1-propanol) at high temperature. Simple collection and removal of the solvent gave products in very good yields that were suitable for further use without additional work-up or purification. Overall, this continuous flow method represents a synthetically useful protocol that is superior to batch processes in terms of shorter reaction times, increased safety, avoidance of work-up procedures, and reduced waste. A brief discussion of the possible mechanism(s) of the reaction is also presented which involves heterogeneous catalysis and/or a Ladenberg rearrangement, with the proposed methyl source as C1 of the primary alcohol.

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Oxygenation of Hydrocarbons Mediated by Mixed-Valent Basic Iron Trifluoroacetate and Valence-Separated Component Species under Gif-Type Conditions Involves Carbon- and Oxygen-Centered Radicals

Cited by 38 publications

References 20 publications

Synthesis, Characterization, and Reactivity of Ferrous and Ferric Oxo/Peroxo Pivalate Complexes in Relation to Gif-Type Oxygenation of Substrates

Synthesis, Characterization, and Reactivity of Ferrous and Ferric Oxo/Peroxo Pivalate Complexes in Relation to Gif-Type Oxygenation of Substrates

In Situ Generation of Carboxylate: An Efficient Strategy for a One-Pot Synthesis of Homo- and Heterometallic Polynuclear Complexes

Flow Synthesis of 2-Methylpyridines via α-Methylation

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