Synthesis and Characterization of Ambient Temperature Stable Organopalladium(IV) Complexes, Including Aryl-, .eta.1-Allyl-, Ethylpalladium(IV), and Pallada(IV)cyclopentane Complexes. Structures of the Poly(pyrazol-1-yl)borate Complexes PdMe3{(pz)3BH} and PdMe3{(pz)4B} and Three Polymorphs of PdMe2Et{(pz)3BH}

Canty, Allan J.; Jin, Hong; Roberts, Andrew S.; Skelton, Brian W.; Traill, Peter R.; White, Allan H.

doi:10.1021/om00001a031

Cited by 58 publications

(38 citation statements)

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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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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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“…[18][19] Furthermore, the observed C-C bond formation reactivity was not affected by the presence of the alkyl radical trap TEMPO, suggesting a non-radical mechanism. 30 Finally, the reaction of 3 with MeI gave ethane in 89% and 99% yields when 1 equiv or 20 equiv of MeI were used, respectively, suggesting a rapid oxidative addition to generate a [( TsMe N4)Pd IV Me3] + intermediate, [31][32][33][34][35][36][37] followed by C-C reductive eliminate to form ethane (Scheme 5).…”

Section: Resultsmentioning

confidence: 99%

Improved Oxidative C-C Bond Formation Reactivity of High-Valent Pd Complexes Supported by a Pseudo-Tridentate Ligand

Schultz¹,

Rath²,

Mirica

2020

Preprint

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There is a large interest in developing oxidative transformations catalyzed by palladium complexes that employ environmentally friendly and economical oxidizing reagents such as dioxygen. Recently, we have reported the isolation and characterization of various mononuclear PdIII and PdIV complexes supported by the tetradentate ligands N,N’-di-alkyl-butyl-2,11-diaza[3.3](2,6)pyridinophane (RN4, R = tBu, iPr, Me), and the aerobically-induced C-C and C-heteroatom bond formation reactivity was investigated in detail. Given that the steric and electronic properties of the multidentate ligands were shown to tune the stability and reactivity of the corresponding high-valent Pd complexes, herein we report the use of an asymmetric N4 ligand, N-mehtyl-N’-tosyl-2,11-diaza[3.3](2,6)pyridinophane (TsMeN4), in which one amine N atom contains a tosyl group. The N-Ts donor atom exhibits a markedly reduced donating ability, which led to the formation of transiently stable PdIII and PdIV complexes, and consequently the corresponding O2 oxidation reactivity and the subsequent C-C bond formation was improved significantly.

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“…In addition, Carmona et al prepared the palladated o-xylene derivative 32 from the corresponding di-Grignard reagent (Scheme 23). [30b] Some of these σ-dialkyl Pd(II) complexes have served as useful platforms to get the C,C-palladacycles 33, containing a Pd(IV) center, via the oxidative addition of alkyl halides, such as MeI and PhCH 2 Br, [31] or reagents like I 2 , Br 2 , dichloroiodobenzene [32] and diaryliodonium salts [33] (Scheme 24).…”

Section: Synthesis Involving Transmetalation Reactionsmentioning

confidence: 99%

Chasing C,C‐Palladacycles

Garcı́a-López

Saura‐Llamas

2021

Eur J Inorg Chem

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The different approaches for the synthesis of C,C-palladacycles are reviewed in this manuscript. These species hold a bidentate ligand that chelates the Pd atom through two C-donor moieties. Their relevance is closely related to the fact that they are intermediates in many palladium-catalyzed transformations. Furthermore, some of them have been used as efficient catalyst in cross coupling reactions. The review is structured according to the different strategies that have been employed to achieve the synthesis of the C,C-palladacycle derivatives, starting with those involving one elemental step (such as the oxidative addition of strained CÀ C bonds to Pd(0) or the transmetalation reactions between organometallic reagents and Pd(II) precursors), and continuing with more complex processes, where at least two elementary steps of Pd chemistry are involved (for example, carbometalation of alkenes followed by a CÀ H activation process). A final section highlights some aspects of synthetic methodologies based on Pd catalysis in which one or several C,C-palladacyclic intermediates are involved.Lenarda et al. synthesized the first reported four-membered C,C-palladacycles 1 a and 1 b in 1972, [5] via the oxidative addition of 1,1,2,2-tetracyanocyclopropane to [Pd(PPh 2 R) 4 ] (R = Ph; Me) (Scheme 1). The reaction occurred with the CÀ C bond cleavage of the highly strained ring and oxidative addition of the two resulting fragments to Pd(0).

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Cited by 58 publications

References 4 publications

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

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

Improved Oxidative C-C Bond Formation Reactivity of High-Valent Pd Complexes Supported by a Pseudo-Tridentate Ligand

Chasing C,C‐Palladacycles

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