Activation volumes for intramolecular oxidative C–X (X = H, F, Cl or Br) addition to platinum(II) imine complexes as a proof of the intimate mechanism

Crespo, Margarita; Martínez, M.; Pablo, Esther de

doi:10.1039/a606872c

Cited by 53 publications

(67 citation statements)

References 21 publications

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“…231 Of all the C-X bonds, the activation of the C-F bond seems to be the most difficult but it can nevertheless be achieved in preference to C-H bonds. 234,232,235 Full kinetic studies have been performed as a function of temperature and pressure leading to activation enthalpies, entropies and volumes providing the most detailed kinetic information that we have available for C-H and C-F bond activation for any reaction. 234 A comparison between the activation parameters for the oxidative addition of C-X bonds at Pt II shows a remarkably low value for H ‡ in the C-F bond activation compared to that for the weaker C-H or C-Cl bonds.…”

Section: Scheme 32 Photo-induced Cyclometalation At Cprh 228176mentioning

confidence: 99%

“…234,232,235 Full kinetic studies have been performed as a function of temperature and pressure leading to activation enthalpies, entropies and volumes providing the most detailed kinetic information that we have available for C-H and C-F bond activation for any reaction. 234 A comparison between the activation parameters for the oxidative addition of C-X bonds at Pt II shows a remarkably low value for H ‡ in the C-F bond activation compared to that for the weaker C-H or C-Cl bonds. These very low values are compensated by the more negative S ‡ values for all the substrates, suggesting that a rearrangement to put the C-F bond in the correct orientation takes place before the activation.…”

Section: Scheme 32 Photo-induced Cyclometalation At Cprh 228176mentioning

confidence: 99%

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Selectivity of C–H Activation and Competition between C–H and C–F Bond Activation at Fluorocarbons

2017

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Partially fluorinated alkanes, arenes, and alkenes can be transformed by a variety of transition metal and lanthanide systems. Although the C-H bond is weaker than the C-F bond regardless of the hybridization of the carbon, the reaction of the C-F bond at the metal is usually more exothermic than the corresponding reaction of the C-H bonds. Both bonds are activated by the metal systems, but the preference for activating these bonds depends on the nature of the hydrocarbon and of the metal system, so that the reaction can be directed exclusively toward C-H or C-F bonds or yield a mixture of products. Additionally, the presence of fluorine differentiates between C-H bonds at different positions resulting in regioselective C-H bond activation; paradoxically, the strongest C-H bond reacts preferentially. The purpose of this review is to describe the field of reactions of partially fluorinated substrates with transition metal atoms, ions, and molecular complexes. The controlling physical properties (thermodynamics and kinetics) are described first, followed by a description of stoichiometric reactions, with the competition between the C-H and C-F activations as focus. A few representative catalytic systems are discussed. The review also highlights the benefit of combining experimental and theoretical studies.

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Section: Scheme 32 Photo-induced Cyclometalation At Cprh 228176mentioning

confidence: 99%

Section: Scheme 32 Photo-induced Cyclometalation At Cprh 228176mentioning

confidence: 99%

Selectivity of C–H Activation and Competition between C–H and C–F Bond Activation at Fluorocarbons

2017

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“…In fact, we have performed some kinetico-mechanistic studies of C-H bond activation on Pt(II) complexes. [39][40][41][42][43] Nevertheless, Pd(IV)-H bonds are only feasible for compounds with high electronegativity ligands, [44][45][46] furthermore, cyclometalation reactions via C-H bond activation on Pd(IV) species have been reported only very recently. 47,48 The common cyclometalation reaction involved in C-H bond activation on both d 8 Pd(II) and d 7 Rh(II) complexes has been traditionally referred to as an electrophilic substitution process (Scheme 1, top).…”

Section: The C-h Bond Cyclometallation Reactions In a Mechanistic Con...mentioning

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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“…It should be mentioned that Crespo et al have obtained kinetic evidence for a concerted oxidative addition of fluoroaromatic substituents in imines at platinum. 10 The hexafluorobenzene compound [Ni(h 2 -C 6 F 6 ){tBu 2 P(CH 2 ) 2 PtBu 2 }] has also been synthesised and it has been shown that on heating it reacts to form [NiF(C 6 F 5 ){tBu 2 P(CH 2 ) 2 PtBu 2 }], but no kinetics are reported. 11 Tsou and Kochi studied the reactions of [Ni(PEt 3 ) 4 ] with Ar-X (X = I, Br, Cl) and showed that there are two competing pathways leading to [Ni II (PEt 3 ) 2 (Ar)X] and [Ni I (PEt 3 ) 3 X] + ArH, respectively.…”

Section: C-f Activation Reactions Of Fluorinated Heterocycles At Nick...mentioning

confidence: 99%

Routes to fluorinated organic derivatives by nickel mediated C–F activation of heteroaromatics

2002

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Activation volumes for intramolecular oxidative C–X (X = H, F, Cl or Br) addition to platinum(II) imine complexes as a proof of the intimate mechanism

Cited by 53 publications

References 21 publications

Selectivity of C–H Activation and Competition between C–H and C–F Bond Activation at Fluorocarbons

Selectivity of C–H Activation and Competition between C–H and C–F Bond Activation at Fluorocarbons

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

Routes to fluorinated organic derivatives by nickel mediated C–F activation of heteroaromatics

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