Activation of saturated hydrocarbons by metal complexes in solution

Шилов, А. Е.; Shteinman, A. A.

doi:10.1016/s0010-8545(00)80336-7

Cited by 170 publications

(69 citation statements)

References 111 publications

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“…[3,4] These early reports of aromatic and aliphatic hydrocarbons C-H activation have been highly influential for the organometallic chemistry community since then. The tremendous industrial and technological implications of effective catalytic C-H activation and functionalization processes have motivated intense research efforts.…”

Section: Introductionmentioning

confidence: 99%

“…The tremendous industrial and technological implications of effective catalytic C-H activation and functionalization processes have motivated intense research efforts. A wide variety of experimental and theoretical investigations have been published which have helped elucidate the underlying mechanism of what is commonly referred to as "Shilov chemistry" [4][5][6] and other C-H activating schemes. [7][8][9][10][11][12] Model systems more amenable to spectroscopic monitoring than the original Pt salts in aqueous media were needed, and the Bercaw group first reported that a tmeda-Pt II complex was capable of activating C-H bonds.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis, Characterization, and Protonation Reactions of Ar‐BIAN and Ar‐BICAT Diimine Platinum Diphenyl Complexes

2010

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PtII diphenyl complexes (N–N)PtPh2 [N–N = diimines Ar–N=C(An)C=N–Ar with Ar = substituted aryl groups] have been prepared and characterized by 1H, 13C, and 195Pt NMR spectroscopy. The 195Pt NMR spectroscopic data establish the electronic influence exerted by substituents at the backbone of the diimine ligand system to the metal center. When compared to diimines Ar–N=CMe–CMe=N–Ar, the electron‐withdrawing ability of the Ar‐BIAN ligand and the electron‐donating ability of the O,O‐heterocyclic Ar‐BICAT systems are demonstrated. Trends in 195Pt NMR chemical shifts suggest that electronic tuning of the metal center is better achieved through variations of the diimine backbone substituents rather than variation of the substituents at the N‐Aryl groups. Protonation of (N–N)PtPh2 in dichloromethane/acetonitrile at –78 °C furnishes the corresponding PtIV hydrides (N–N)PtPh2H(NCMe)+. The PtIV hydrides liberate benzene with the formation of (N–N)PtPh(NCMe)+ when the temperature is raised. A second protonation and rapid benzene elimination produces the dicationic PtII species (N–N)Pt(NCMe)22+ at approximately 50 °C. Protonation of (N–N)PtPh2 in the absence of acetonitrile results in the clean formation of (N–N)PtPh(η2‐C6H6)+ at temperatures that depend on the steric hindrance provided by the alkyl substituents at the diimine N‐aryl groups. These findings support the notion that the metal is the kinetically preferred site of protonation. The results qualitatively agree with a recent mechanistic study of protonation‐induced reactions of (diimine)PtPh2 complexes that bear simple methyl substituents at the diimine backbone. Several compounds have been crystallographically characterized. All complexes have the expected square planar environment at the metal. Modest variations in the metric parameters suggest that the Ar‐BICAT system has a weaker trans influence than the Ar‐BIAN and Ar‐DAB systems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization, and Protonation Reactions of Ar‐BIAN and Ar‐BICAT Diimine Platinum Diphenyl Complexes

2010

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“…A reasonable mechanistic scheme for the catalytic cycle (Figure 1) was proposed by Shilov not long after his initial report of the oxidation (19,20). In the first step of this cycle, a methylplatinum(II) intermediate is formed by reaction of Pt(II) with alkane.…”

Section: "Electrophilic" Systemsmentioning

confidence: 90%

Organometallic C—H Bond Activation: An Introduction

Goldman¹,

Goldberg²

2004

ACS Symposium Series

113

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An introduction to the field of activation and fimctionalization of C-H bonds by solution-phase transition -metal-based systems is presented, with an emphasis on the activation of aliphatic C-H bonds. The focus of this chapter is on stoichiometric and catalytic reactions that operate via organometallic mechanisms, i.e., those in which a bond is formed between the metal center and the carbon undergoing reactionThe carbon-hydrogen bond is the un-functional group. Its unique position in organic chemistry is well illustrated by the standard representation of organic molecules: the presence of C-H bonds is indicated simply by the absence of any other bond. This "invisibility" of C-H bonds reflects both their ubiquitous nature and their lack of reactivity. With these characteristics in mind it is clear that if the ability to selectively fiinctionalize C-H bonds were well developed, it could potentially constitute the most broadly applicable and powerful class of transformations in organic synthesis. Realization of such potential could revolutionize the synthesis of organic molecules ranging in complexity from methanol to the most elaborate natural or unnatural products.The following chapters in this volume offer a view of many of the current leading research efforts in this field, in particular those focused on the activation

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“…The branched radical i-C 3 F 7 is substantially more reactive than linear n-C 4 F 9 , also indicating the importance of polar effects in the transition structures for hydrogen abstractions: the 28:18 selectivities for n-heptane are higher than for the relatively selective t-BuO radical (vide supra). [148] 3.4 Phase-Transfer Catalyzed Alkane Halogenations Our recently developed [145] phase-transfer catalytic (PTC) alkane halogenation protocol is useful for chlorinations, [149] brominations, [150] and iodinations [151] of unactivated, aliphatic hydrocarbons, which may be linear, branched, and (poly)cyclic, strained as well as unstrained.…”

Section: Reviewsmentioning

confidence: 99%

“…Despite enormous efforts, alkane functionalizations with heavy metals like platinum [9,14] and mercury, [15] or through oxidative additions of bare metals [16] as well as transition metal complexes, [8] are still far from industrial utilization. As usual, Nature is much more advanced and a number of enzymes accomplish selective alkane oxygenations (e.g., with cytochrome P-450, [17] methane monooxygenase [18] and others [19] ).…”

Section: Introductionmentioning

confidence: 99%

Metal‐Free, Selective Alkane Functionalizations

2003

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The present overview of alkane functionalization reactions presents comparisons between radical and metal-initiated (sometimes metal-catalyzed) methodologies. While metal-catalyzed processes are excellent approaches to this problem, metal-free alternatives are equally if not, at least from an environmental and cost perspective, more useful. This conclusion is supported by the fact that many so-called metal-catalyzed reactions also work without the metal present, and the large variety of metals showing the same product distributions emphasizes that the metal often just aids in the generation of the active species, i.e., the metal itself is not participating in the crucial C À H activation step. Highly selective alkane functionalization reactions such as those derived from nitroxyl and related radicals as well as through radical reactions conducted in phase-transfer catalyzed systems are available but generally underutilized. These systems, in contrast to typical metalcatalyzed approaches, are also applicable to highly strained alkanes and offer the highest 38/28 C À H selectivities reported to date in a radical reaction. The article closes with representative experimental protocols for the PTC bromination of cubane as an example of the applicability of this method to strained hydrocarbons and the direct iodination of cyclohexane as well as adamantane as typical alkanes bearing secondary and tertiary C À H bonds.

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Activation of saturated hydrocarbons by metal complexes in solution

Cited by 170 publications

References 111 publications

Synthesis, Characterization, and Protonation Reactions of Ar‐BIAN and Ar‐BICAT Diimine Platinum Diphenyl Complexes

Synthesis, Characterization, and Protonation Reactions of Ar‐BIAN and Ar‐BICAT Diimine Platinum Diphenyl Complexes

Organometallic C—H Bond Activation: An Introduction

Metal‐Free, Selective Alkane Functionalizations

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