Homogeneous Oxidation of Alkanes by Electrophilic Late Transition Metals

Stahl, Shannon S.; Labinger, Jay A.; Bercaw, John E.

doi:10.1002/(sici)1521-3773(19980904)37:16<2180::aid-anie2180>3.0.co;2-a

Cited by 551 publications

(238 citation statements)

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“…[1][2][3][4] Despite several industrial applications such as the oxidation of cyclohexane and p-xylene, which use O 2 as the oxidant and manganese or cobalt based catalysts, the development of practical oxidation catalysts and a thorough mechanistic understanding of alkane oxidation processes continue to provide great challenges in catalysis research. A number of different classes of alkane oxidation catalysts have been developed during the last 50 years, including the cobalt and manganese acetate catalyst systems used industrially, 5 the heme-based iron complexes containing porphyrin-type ligands used in nature, 6,7 polyoxometalates [8][9][10] and more recently, non-heme iron based catalyst systems.…”

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confidence: 99%

Towards robust alkane oxidation catalysts: electronic variations in non-heme iron(ii) complexes and their effect in catalytic alkane oxidation

et al. 2009

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A series of non-heme iron(II) bis(triflate) complexes containing linear and tripodal tetradentate ligands has been prepared. Electron withdrawing and electron donating substituents in the para position of the pyridine ligands as well the effect of pyrazine versus pyridine and sulphur or oxygen donors instead of nitrogen donors have been investigated. The electronic effects induced by these substituents influence the strength of the ligand field. UV-vis spectroscopy and magnetic susceptibility studies have been used to quantify these effects and VT 1 H and 19 F NMR spectroscopy as well as X-ray diffraction have been used to elucidate structural and geometrical aspects of these complexes. The catalytic properties of the iron(II) complexes as catalysts for the oxidation of cyclohexane with hydrogen peroxide have been evaluated. In the strongly oxidising environment required to oxidise alkanes, catalyst stability determines the overall catalytic efficiency of a given catalyst, which can be related to the ligand field strength and the basicity of the ligand and its propensity to undergo oxidation.2

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Section: Introductionmentioning

confidence: 99%

Towards robust alkane oxidation catalysts: electronic variations in non-heme iron(ii) complexes and their effect in catalytic alkane oxidation

et al. 2009

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“…T he selective activation and functionalization of saturated alkane COH bonds represent important areas of research (1)(2)(3)(4)(5). Alkanes are the main constituents of oil and natural gas; hence the ability to efficiently transform alkanes to more valuable products is highly desirable (1,2).…”

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“…Partial oxidations of alkanes (hydroxylation, oxidative coupling, and oxidative dehydrogenation) are among the few processes that could, in principle, provide valuable products (alcohols, higher alkanes, and alkenes, respectively) in thermodynamically favorable transformations, but such reactions are difficult to carry out with high selectivity at high conversion (1,2,4). More traditional hightemperature routes often proceed by free radical mechanisms, for which the products derived from alkanes are virtually guaranteed to be more reactive than the alkane itself, placing an inherent constraint on selectivity (2)(3)(4).…”

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The role of alkane coordination in C–H bond cleavage at a Pt(II) center

Chen

Labinger

Bercaw

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…Considerable progress has been made during the last three decades regarding the C-H activation of alkanes, in particular electrophilic activation reactions with late transition metals. [1][2][3][4] Once C-H bond cleavage has occurred at a metal centre, a functionalisation of the metal carbon bond is required, followed by release of the product and regeneration of the catalyst. In the case of oxidation reactions, this functionalisation of metal alkyl complexes should be carried out ideally with environmentally benign oxidants such as O 2 or H 2 O 2 .…”

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Towards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum(II)–Methyl Bond

Taylor

Law²,

Sunley³

et al. 2009

Angew Chem Int Ed

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Keywords: singlet oxygen, platinum, photosensitiser, alkane oxidation 2 The selective catalytic oxidation of methane and higher alkanes remains one of the great challenges in catalysis research. Considerable progress has been made during the last three decades regarding the C-H activation of alkanes, in particular electrophilic activation reactions with late transition metals. [1][2][3][4] Once C-H bond cleavage has occurred at a metal centre, a functionalisation of the metal carbon bond is required, followed by release of the product and regeneration of the catalyst. In the case of oxidation reactions, this functionalisation of metal alkyl complexes should be carried out ideally with environmentally benign oxidants such as O 2 or H 2 O 2 . In a previous study, we reported the oxidation of dimethyl Pt II complexes with H 2 O 2 to generate cis-dihydroxo Pt IV complexes. [5] The unusual cis isomer was obtained by using amino-substituted bipyridine ligands, which stabilise this isomer through hydrogen bonding. When we extended our work to Pt II methyl complexes containing tridentate amino-substituted terpyridine ligands, we discovered a remarkable reactivity of the diamino substituted terpy Pt II methyl complex towards O 2 .The reaction of 6,6'-diaminoterpyridine (1) Figure 1 and the supporting material for further information). [6] This dimer formation is quite common for terpy Pt II complexes and arises from metal-metal and π-π interactions. [7] It is for example also observed in the solid state structure of [Pt ( Pt II complexes. [9][10][11] Excitation of the charge transfer region at 388 nm results in an emission spectrum with maxima at 580 and 654 nm (see Supplementary Information).Noteworthy, the diamino substituted terpyridine ligand itself also shows photoluminescence. [12,13] The luminescent behaviour of [Pt (1) [14] In addition, several Pt II and Pt IV complexes containing alkylperoxo ligands other than methylperoxo have been reported previously, but none of these have been prepared via an O 2 insertion reaction. [15][16][17][18][19][20] The O 2 insertion reaction into the Pt II -Me bond in the complex [(PN)Pt(Me)(OOMe)] is also affected by light and the authors have proposed a radical mechanism for their insertion reaction. [14] Similarly, the insertion of O 2 into a Pt IV -H bond has been reported to involve a radical pathway, [21] and insertions of O 2 into other transition metal methyl bonds such as Co and Fe methyl complexes proceed via methyl radicals. [22,23] In contrast, two reports on the direct insertion of O 2 into Pd II -H bonds have shown that these insertion reactions are not affected by light. [24,25] Mechanistic investigations suggest that these reactions proceed by a Pd I /HO 2 (triplet) radical pair intermediate or via a stepwise pathway initiated by reductive elimination of HX to form an O 2 -reactive Pd 0 intermediate. [26,27] Dioxygen, in its triplet ground state, is rather unreactive because reactions are spinforbidden and require a triplet-singlet surface crossing on the reaction c...

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Homogeneous Oxidation of Alkanes by Electrophilic Late Transition Metals

Cited by 551 publications

References 47 publications

Towards robust alkane oxidation catalysts: electronic variations in non-heme iron(ii) complexes and their effect in catalytic alkane oxidation

Towards robust alkane oxidation catalysts: electronic variations in non-heme iron(ii) complexes and their effect in catalytic alkane oxidation

The role of alkane coordination in C–H bond cleavage at a Pt(II) center

Towards Photocatalytic Alkane Oxidation: The Insertion of Dioxygen into a Platinum(II)–Methyl Bond

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