Tilden lecture: shining light on metal catalysts

Evans, John

doi:10.1039/cs9972600011

Cited by 19 publications

(12 citation statements)

References 20 publications

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“…In standard neutron experiments, typical beam sizes are within the 0.1-10 mm range. To push down the available spatial resolution, to date specific optics have been developed using several approaches (Erko, 2008), e.g., Bragg diffraction (Mikula et al, 1986), reflection [in mirrors (Sears, 1989, Kumakhov lenses (Kumakhov and Sharov, 1992), or capillary optics (Chen et al, 1992)] and refraction, in compound refractive lens (Eskildsen et al, 1998;Beguiristain et al, 2002;Shimizu, 2006).…”

Section: Neutron Probesmentioning

confidence: 99%

Materials characterization by synchrotron x-ray microprobes and nanoprobes

et al. 2018

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Section: Neutron Probesmentioning

confidence: 99%

Materials characterization by synchrotron x-ray microprobes and nanoprobes

et al. 2018

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“…Note that one of the authors succeeded in elucidating the mechanism of paramagnetic Fe-catalyzed Kumada–Tamao–Corriu coupling by a solution-phase XAFS analysis . Reviews of XAFS analysis of homogeneous catalysts have been reported . Nevertheless, the detailed mechanistic study of homogeneous catalysis using XAFS remains difficult.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insights on Pd/Cu-Catalyzed Dehydrogenative Coupling of Dimethyl Phthalate

et al. 2018

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Despite its industrial importance, very limited mechanistic information on the dehydrogenative coupling of dimethyl phthalate has been reported. Herein we report the detailed mechanism for dehydrogenative coupling of dimethyl phthalate catalyzed by [Pd(OAc)2]/[Cu(OAc)2]/1,10-phenanthroline·H2O (phen·H2O). The solution-phase analysis of the catalytic system by XANES shows the active species to be Pd(II), and EXAFS supports the formation of an (acetato)(dimethyl phthalyl)(phen)palladium(II) complex from [Pd(OAc)2]. A formation pathway of tetramethyl 3,3′,4,4′-biphenyltetracarboxylate via disproportionation of independently prepared [Pd(OAc){C6H3(CO2Me)2-3,4}(phen)] is observed with regeneration of [Pd(OAc)2(phen)].

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“…Well-defined supported organometallic complexes may be obtained by reaction of molecular precursors with an oxide surface when the grafting conditions are mild and rigorously clean (dry and anaerobic) . Most studies of such systems focus on spectroscopic characterization of surface structures. , Quantitative equilibrium measurements, or kinetic studies of catalytic reactivity, − are uncommon and usually predicated on analyses of product ratios. In this report, we present the first kinetic study of stoichiometric surface reactions in a series of supported organometallic complexes which form alkylidenes.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanisms of Thermally Induced Alkane Eliminations from Silica-Supported Bis(alkyl)chromium(IV) and -vanadium(IV) Complexes

1998

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Silica-supported bis(alkyl) complexes of Cr(IV) and V(IV), (tSiO) 2 M(CH 2 R) 2 , undergo surprisingly clean thermal transformations to generate supported alkylidene complexes, (tSiO) 2 MdCHR, with concurrent liberation of RCH 3 . The reactions are quantitative and kinetically first order, suggesting that all surface organometallic complexes possess or can access very similar coordination environments. Isotope-labeling and kinetics experiments support a mechanistic assignment of intramolecular R-H elimination. In the case of the Cr complexes, the temperature dependences of the first-order rate constants give nonlinear Eyring plots that are concave downward. A two-step mechanism of reversible (alkyl)(alkylidene)Cr VI hydride formation followed by reductive elimination of alkane is proposed. This mechanism is not accessible for V(IV), therefore concerted R-H elimination is considered more likely. The activation parameters for the thermolysis of (tSiO) 2 V(CH 2 -SiMe 3 ) 2 , obtained from the linear Eyring plot, are ∆H q ) (11.0 ( 1.0) kcal/mol and ∆S ‡ ) (-43 ( 3) cal K -1 mol -1 . The large negative value of ∆S ‡ is suggestive of surface assistance for R-H elimination.

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Tilden lecture: shining light on metal catalysts

Cited by 19 publications

References 20 publications

Materials characterization by synchrotron x-ray microprobes and nanoprobes

Materials characterization by synchrotron x-ray microprobes and nanoprobes

Mechanistic Insights on Pd/Cu-Catalyzed Dehydrogenative Coupling of Dimethyl Phthalate

Kinetics and Mechanisms of Thermally Induced Alkane Eliminations from Silica-Supported Bis(alkyl)chromium(IV) and -vanadium(IV) Complexes

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