Kinetics, Spectroscopy, and Computational Chemistry of Arylnitrenes

Gritsan, Nina P.; Platz, Matthew S.

doi:10.1021/cr040055+

Cited by 231 publications

(258 citation statements)

References 140 publications

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“…Thus, photolysis of matrix-isolated (argon, 10 K) phenyl azide 7 a produces mixtures of phenyl nitrene 1, azirine 5 a, and ketenimine 6 a in photostationary equilibria, and the yield of nitrene 1 is low (Scheme 1). [6] Fluorine substituents in the ortho positions of 1 decrease the tendency of these rearrangements, [7] and therefore ortho-fluorinated phenyl nitrenes are obtained in higher yields under the same conditions. [5][6]8] The only nitreno radicals 4 that could be matrix-isolated and spectroscopically characterized are therefore those bearAbstract: The photochemistry of 2-iodo-3,4,5,6-tetrafluorophenyl azide (7 d) has been investigated in argon and neon matrices at 4 K, and the products characterized by IR and EPR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

3,4,5,6‐Tetrafluorophenylnitren‐2‐yl: A Ground‐State Quartet Triradical

Grote

Finke

Koßmann

et al. 2010

Chemistry A European J

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The photochemistry of 2-iodo-3,4,5,6-tetrafluorophenyl azide (7 d) has been investigated in argon and neon matrices at 4 K, and the products characterized by IR and EPR spectroscopy. The primary photochemical step is loss of a nitrogen molecule and formation of phenyl nitrene 1 d. Further irradiation with UV or visible light results in mixtures of 1 d with azirine 5 d', ketenimine 6 d', nitreno radical 2 d, and azirinyl radical 9. The relative amounts of these products strongly depend on the matrix and on the irradiation conditions. Nitreno radical 2 d with a quartet ground state was characterized by EPR spectroscopy. Electronic structure calculations in combination with the experimental results allow for a detailed understanding of the properties of this unusual new type of organic high-spin molecules.

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Section: Introductionmentioning

confidence: 99%

3,4,5,6‐Tetrafluorophenylnitren‐2‐yl: A Ground‐State Quartet Triradical

Grote

Finke

Koßmann

et al. 2010

Chemistry A European J

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“…This analytical method (20)(21)(22)(25)(26)(27)(28) provides direct evidence for Rhnitrene formation and the ability of this two-electron oxidant to react through hydrogen atom abstraction. Previous studies using computational and spectroscopic methods estimate that the nitrenoid species has a half-life in the nanosecond to microsecond regime (29)(30)(31)(32), underscoring the impressive capabilities of DESI-MS to capture transient intermediates in solution-phase catalytic cycles of complex reactions. It should be recognized, however, that this mass spectrometric study identifies numerous transient species, but does not explicitly establish the kinetic competency of a particular species on the reaction coordinate.…”

mentioning

confidence: 99%

Capturing fleeting intermediates in a catalytic C–H amination reaction cycle

Perry

Cahill

Roizen

et al. 2012

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

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We have applied an ambient ionization technique, desorption electrospray ionization MS, to identify transient reactive species of an archetypal C-H amination reaction catalyzed by a dirhodium tetracarboxylate complex. Using this analytical method, we have detected previously proposed short-lived reaction intermediates, including two nitrenoid complexes that differ in oxidation state. Our findings suggest that an Rh-nitrene oxidant can react with hydrocarbon substrates through a hydrogen atom abstraction pathway and raise the intriguing possibility that two catalytic C-H amination pathways may be operative in a typical bulk solution reaction. As highlighted by these results, desorption electrospray ionization MS should have broad applicability for the mechanistic study of catalytic processes.mass spectrometry | transient intermediates | C-H oxidation | catalysis C atalytic methods for selective C-H oxidation rely on the exquisite choreography of a series of ligand substitution and redox events (1, 2) and in some instances, the controlled generation of a hyperreactive electrophile (3-5). The Du Bois laboratory has developed an amination protocol that uses the catalyst bis [rhodium(α,α,α′,α′-tetramethyl-1,3-benzenedipropionic acid)], hereafter designated as Rh 2 (esp) 2 , to promote both intra-and intermolecular oxidation reactions (1, 2). Indirect evidence has implicated a reactive Rh-nitrene intermediate that oxidizes saturated C-H bonds through a concerted asynchronous two-electron insertion event (6-10). Studies of the reaction mechanism suggest the generation of a one-electron oxidized form of the catalyst, [Rh 2 (esp) 2 ]+ , which appears to result from reaction of the nitrenoid oxidant (4, 5, 11). The fast rates of the on-and off-path steps in this catalytic process and the transient nature of the reactive Rh-nitrene have confounded direct detection of many of the proposed reaction intermediates.A preponderance of experimental and theoretical data (7-10, 12, 13) supports the mechanism for Rh-catalyzed C-H amination depicted in Fig. 1. Sulfamate 2 and iodine oxidant 3 condense to form iminoiodinane 4 (14, 15). The iminoiodinane is a ligand for Rh 2 (esp) 2 , which react to generate [Rh 2 (esp) 2 ]•PhINSO 2 OR 5; subsequent loss of iodobenzene (PhI) furnishes nitrenoid 6. Oxidation of adamantane by 6 gives the sulfonamide product 7 and regenerates the dirhodium catalyst 1. The structures of intermediates 5 and 6 were postulated through analogy to carbenoid intermediates in reactions of dirhodium catalysts with diazo compounds, and to the best of our knowledge, have not been observed spectroscopically (6-10, 12, 13). In our experience, the oxidation of substrate by Rh-nitrene 6 seems to correlate with competitive formation of a mixed-valent (Rh 2+ /Rh 3+ ) dimer 8 that visibly colors the reaction solution red. Previous studies show that this red species is generated when Rh 2 (esp) 2 1, sulfamate 2, and oxidant 3 are mixed in solution (e.g., 0.3 mM 1 in chlorobenzene) (4,5,11). In this report, we provide direct...

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“…138,139 It is known that nitrene which possesses an electronically active open shell structure can be generated by light irradiation on aryl azide with ultraviolet light and discharging nitrogen. 140 This nitrene rapidly reacts with carbon monoxide or oxygen molecules, providing isocyanato or nitro compounds, respectively. 141 With this interesting azide property, we synthesized a new PCP with a ligand bearing an azide moiety and obtained a colorless crystal [Zn 2 (N 3 -ipa) 2 (bpy) 2 (DMF) 1.5 ] n (CID-N 3 ) by the reaction of 5-azidoisophthalic acid, bpy and Zn(NO 3 ) 2 ¢ 6H 2 O in a mixed solution of DMF and methanol.…”

Section: Light Responsive Pcp For On-demandmentioning

confidence: 99%

Design and Synthesis of Porous Coordination Polymers Showing Unique Guest Adsorption Behaviors

Matsuda

2013

Bulletin of the Chemical Society of Japan

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Gas storage and separation are becoming a high priority area of research due to economic, industrial, and environmental reasons. The last two decades have therefore witnessed dramatic growth in the search for more efficient and adaptable nanoporous materials. In particular, much attention has been focused on porous coordination polymers (PCPs) or metal organic frameworks (MOFs) as new nanoporous materials. Based on the unlimited combination of metal ions and organic ligands, PCPs can provide infinite variety of nanospace in their pores. As molecular adsorption is dependent on the size, shape, and surface nature of nanospace, many unique molecular adsorption or trapping phenomena have been reported in this class of compounds. In this account, I focus on how thoughtful design can lead to the synthesis of porous coordination polymers that demonstrate unprecedented adsorption behavior not found in other porous materials. Examples include selective adsorption of acetylene over carbon dioxide in the CPL series of PCPs, using charge-transfer to induce selective adsorption of nitric oxide and oxygen in TCNQ (7,7,8,8-tetracyano-p-quinodimethane) based PCP and lightinduced on-demand adsorption and structural transformations in CID-based PCPs. The guidelines underpinning such unique, highly selective guest adsorption are discussed.

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Kinetics, Spectroscopy, and Computational Chemistry of Arylnitrenes

Cited by 231 publications

References 140 publications

3,4,5,6‐Tetrafluorophenylnitren‐2‐yl: A Ground‐State Quartet Triradical

3,4,5,6‐Tetrafluorophenylnitren‐2‐yl: A Ground‐State Quartet Triradical

Capturing fleeting intermediates in a catalytic C–H amination reaction cycle

Design and Synthesis of Porous Coordination Polymers Showing Unique Guest Adsorption Behaviors

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