Chemical Kinetics as a Mechanistic Tool

Bakač, Andreja

doi:10.1002/9780470602539.ch8

Cited by 12 publications

(14 citation statements)

References 110 publications

(38 reference statements)

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“…† The TIP value is large but reasonable considering the accessibility of other electronic isomers and the proximity of spin excited states with larger S values. 23 , 24 Further supporting this model, the magnetization trends toward saturation between 2–3 μ B as the field is increased to 5 T at 1.8 K (Fig. S8 † ), consistent with S = 3/2 where g < 2 and significant axial anisotropy is observed.…”

Section: Resultssupporting

confidence: 74%

Bimetallic iron–iron and iron–zinc complexes of the redox-active ONO pincer ligand

et al. 2016

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Section: Resultssupporting

confidence: 74%

Bimetallic iron–iron and iron–zinc complexes of the redox-active ONO pincer ligand

et al. 2016

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“…The amount of information that can be extracted from well-behaved systems is enormous. The present situation of instrumentation 30 and chemometrics [31][32][33][34] is such that only a very small number of systems are out of the scope of possible time-resolved studies. Low-temperature stopped-flow, kinetic measurements under inert atmosphere, dynamic NMR and work at elevated pressures have become increasingly common.…”

Section: Manuel Martínezmentioning

confidence: 99%

Kinetico-mechanistic studies of cyclometalating C–H bond activation reactions on Pd(ii) and Rh(ii) centres: The importance of non-innocent acidic solvents in the process

Granell

Martínez

2012

Dalton Trans.

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The activation of C-H bonds in homogeneous systems has been the subject of study for many years due to its involvement in important industrial catalytic processes. A large number of reviews on the different areas involved have appeared, but those dealing with kinetic studies, including activation parameters, are rather scarce due to the severe difficulties in interpreting experimental data. In this perspective, the information available from kinetico-mechanistic studies of cyclometalation reactions on Pd(II) and Rh(II) centres via C-H bond activation is considered. Experimental results from studies performed on complexes of these metal centres indicate that the historically accepted electrophilic substitution classification is not a satisfactory mechanistic term for the process occurring during the reaction. A definite acid-assisted phenomenon is evident for all the processes studied, which contradicts the expected need for a proton abstractor in the reaction. This is even more surprising when considering the expected hydrolysis of M-C bonds in such acidic media, indicating that metalation prevails under these conditions. Only the presence of coordinated acid molecules in solvolytic carboxylic acid media can explain the observations. The fine tuning between the proton abstraction capacity of a coordinated RCO(2)H molecule and its Lewis basicity results in a unique reactivity trend. DFT calculations carried out for these acid-assisted processes fully agree with the experimental trends observed.

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“…A stable trans-dihydride complex trans-(PNP)Ru(H) 2 (CO) (3) is therefore formed through TS 2,3 with a free energy barrier of 26.9 kcal/mol (1 → TS 2,3 ) for H 2 cleavage. When a dimethyl carbonate molecule approaches 3, it takes a hydride directly from Ru to its unsaturated carbon and forms an anionic ligand (MeO) 2 CHO − through transition state TS 3,4 ( Figure 2) with a free energy barrier of 24.3 kcal/mol (3 → TS 3,4 ). An unstable hydrido alkoxo complex 4 is therefore formed.…”

Section: ■ Introductionmentioning

confidence: 99%

Metal Hydride and Ligand Proton Transfer Mechanism for the Hydrogenation of Dimethyl Carbonate to Methanol Catalyzed by a Pincer Ruthenium Complex

Yang

2012

ACS Catal.

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The hydrogenation of dimethyl carbonate to methanol catalyzed by a PNN-ligated ruthenium complex (PNN)Ru(CO)(H) was studied computationally using the density functional theory at the range-separated and dispersion-corrected ωB97X-D functional level in conjunction with an all-electron 6-31++G(d,p) basis set (Stuttgart ECP28MWB basis set for Ru). A direct metal hydride and ligand proton transfer mechanism with three cascade catalytic cycles for the hydrogenation of dimethyl carbonate, methyl formate, and formaldehyde to methanol is proposed. The resting state in the catalytic reaction is the trans dihydride complex trans-(PNN)Ru(H) 2 (CO). Calculation results indicate that the rate-determining step in the whole reaction is the formation of the second methanol molecule through simultaneous breaking of a C−OCH 3 bond and transferring a ligand methylene proton to the dissociated CH 3 O − in the catalytic cycle for hydrogenation of methyl formate. The essential role of the noninnocent PNN pincer ligand is to split H 2 and assist methanol formation through the aromatization and dearomatization of the pyridine ring in the ligand. A new iron pincer complex, trans-(PNN)Fe(H) 2 (CO), is proposed and evaluated as a promising low-cost and high efficiency catalyst for this reaction.

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Chemical Kinetics as a Mechanistic Tool

Cited by 12 publications

References 110 publications

Bimetallic iron–iron and iron–zinc complexes of the redox-active ONO pincer ligand

Bimetallic iron–iron and iron–zinc complexes of the redox-active ONO pincer ligand

Kinetico-mechanistic studies of cyclometalating C–H bond activation reactions on Pd(ii) and Rh(ii) centres: The importance of non-innocent acidic solvents in the process

Metal Hydride and Ligand Proton Transfer Mechanism for the Hydrogenation of Dimethyl Carbonate to Methanol Catalyzed by a Pincer Ruthenium Complex

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