Powerful Insight into Catalytic Mechanisms through Simultaneous Monitoring of Reactants, Products, and Intermediates

Vikse, Krista L.; Ahmadi, Zohrab; Manning, Cara C.; Harrington, David A.; McIndoe, J. Scott

doi:10.1002/ange.201102630

Cited by 47 publications

(28 citation statements)

References 32 publications

(26 reference statements)

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“…This was supported by DFT calculations, which showed that while oxidative addition of iodobenzene to the mononuclear complex Me 3 PAuI has a high activation barrier (132.2 kJ mol À1 ), the related reaction for the bare gold cluster Au 38 has a substantially lower barrier (47.3 kJ mol À1 ). [2c] Gas-phase studies represent a powerful way of uncovering the intrinsic reactivity of metallic ions [6,7] and the mechanisms of their CÀX bond activation reactions. [8] The stoichiometry of the metallic reactant ion can be confidently assigned by the unique mass and often-distinctive isotopic signature of the metal.…”

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confidence: 99%

Gold‐Mediated CI Bond Activation of Iodobenzene

et al. 2012

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Controversy resolved! A combination of gas-phase ion-molecule reactions and theoretical studies confirm bisligated mononuclear Au(I) complexes are unable to undergo oxidative addition of iodobenzene for Sonogashira coupling, but that the ligated gold clusters [Au(3)L(n)](+) (L=Ph(2)P(CH(2))(n)PPh(2); n=3-6) activate the C-I bond. DFT calculations on the transition states show that the linker size n tunes the cluster reactivity.

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confidence: 99%

Gold‐Mediated CI Bond Activation of Iodobenzene

et al. 2012

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“…high ‘ESI‐MS response’). We have published simple approaches to the preparation of these charged tags for phosphines, aryl halides and alkynes using [–CH 2 PPh 3 ][PF 6 ] as the spectrometric handle, typically in two steps: treatment of triphenylphosphine with a functionalized alkyl halide followed by a salt metathesis to replace the halide counterion with a non‐coordinating counterion. The more weakly coordinating the counterion, the better, in order to minimize ion pairing and enhance signal intensity.…”

Section: Selection Of Suitable Ions and Counter‐ionsmentioning

confidence: 99%

“…We could simultaneously detect the aryl iodide, the diaryl acetylene product, the aryl byproduct of dehalogenation and two palladium‐containing intermediates, L 2 Pd(Ar)I and L 2 Pd(Ar)(C 2 Ph) (Fig. ) . The data on appearance of product was well‐matched to data collected through other techniques ( 1 H NMR and UV/Vis analysis), and the data could be matched closely to a numerical model.…”

Section: Continuous Reaction Monitoringmentioning

confidence: 99%

Practical approaches to the ESI-MS analysis of catalytic reactions

2014

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Electrospray ionization mass spectrometry (ESI-MS) is a soft ionization technique commonly coupled with liquid or gas chromatography for the identification of compounds in a one-time view of a mixture (for example, the resulting mixture generated by a synthesis). Over the past decade, Scott McIndoe and his research group at the University of Victoria have developed various methodologies to enhance the ability of ESI-MS to continuously monitor catalytic reactions as they proceed. The power, sensitivity and large dynamic range of ESI-MS have allowed for the refinement of several homogenous catalytic mechanisms and could potentially be applied to a wide range of reactions (catalytic or otherwise) for the determination of their mechanistic pathways. In this special feature article, some of the key challenges encountered and the adaptations employed to counter them are briefly reviewed.

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“…However, it is often difficult to obtain detailed molecular mechanistic information under normal operating conditions because intermediates have short lifetimes (typically less than~1 s), exist in a complex and dynamic matrix involving multiple reaction pathways, and have low concentrations [2][3][4][5]. These difficulties are significantly more pronounced for homogenous multi-catalytic systems [6], which show great promise for rapidly achieving onepot complex transformations that improve efficiency, selectivity, and enantiomeric purity.…”

Section: Introductionmentioning

confidence: 99%

Multistage Reactive Transmission-Mode Desorption Electrospray Ionization Mass Spectrometry

Peters

Comi

Perry

2015

J. Am. Soc. Mass Spectrom.

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Abstract. Elucidating reaction mechanisms is important for advancing many areas of science such as catalyst development. It is often difficult to probe fast reactions at ambient conditions with high temporal resolution. In addition, systems involving reagents that cross-react require analytical methods that can minimize interaction time and specify their order of introduction into the reacting system. Here, we explore the utility of transmission mode desorption electrospray ionization (TM-DESI) for reaction monitoring by directing a microdroplet spray towards a series of meshes with micrometer-sized openings coated with reagents, an approach we call multistage reactive TM-DESI (TM n -DESI, where n refers to the number of meshes; n=2 in this report). Various stages of the reaction are initiated at each mesh surface, generating intermediates and products in microdroplet reaction vessels traveling towards the mass spectrometer. Using this method, we investigated the reactivity of iron porphyrin catalytic hydroxylation of propranolol and other substrates. Our experimental results indicate that TM n -DESI provides the ability to spatially separate reagents and control their order of introduction into the reacting system, thereby minimizing unwanted reactions that lead to catalyst deactivation and degradation products. In addition, comparison with DESI-MS analyses (the Zare and Latour laboratories published results suggesting accessible reaction times <1 ms) of the reduction of dichlorophenolindophenol by L-ascorbic acid suggest that TM 1 -DESI can access reaction times less than 1 ms. Multiple meshes allow sequential stages of desorption/ionization per MS scan, increasing the number of analytes and reactions that can be characterized in a single experiment.

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Powerful Insight into Catalytic Mechanisms through Simultaneous Monitoring of Reactants, Products, and Intermediates

Cited by 47 publications

References 32 publications

Gold‐Mediated CI Bond Activation of Iodobenzene

Gold‐Mediated CI Bond Activation of Iodobenzene

Practical approaches to the ESI-MS analysis of catalytic reactions

Multistage Reactive Transmission-Mode Desorption Electrospray Ionization Mass Spectrometry

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