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• 244187-81-3 1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene 

Relevant academic research and scientific papers

Insight into the efficiency of cinnamyl-supported precatalysts for the suzuki-miyaura reaction: Observation of Pd(I) dimers with bridging allyl ligands during catalysis

Despite widespread use of complexes of the type Pd(L)(η3- allyl)Cl as precatalysts for cross-coupling, the chemistry of related Pd I dimers of the form (μ-allyl)(μ-Cl)Pd2(L) 2 has been underexplored. Here, the relationship between the monomeric and the dimeric compounds is investigated using both experiment and theory. We report an efficient synthesis of the PdI dimers (μ-allyl)(μ-Cl)Pd2(IPr)2 (allyl = allyl, crotyl, cinnamyl; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) through activation of Pd(IPr)( η3-allyl)Cl type monomers under mildly basic reaction conditions. The catalytic performance of the PdII monomers and their PdI μ-allyl dimer congeners for the Suzuki-Miyaura reaction is compared. We propose that the (μ-allyl)(μ-Cl) Pd2(IPr)2-type dimers are activated for catalysis through disproportionation to Pd(IPr)( η3-allyl)Cl and monoligated IPr-Pd0. The microscopic reverse comproportionation reaction of monomers of the type Pd(IPr)( η3-allyl)Cl with IPr-Pd0 to form PdI dimers is also studied. It is demonstrated that this is a facile process, and PdI dimers are directly observed during catalysis in reactions using PdII precatalysts. In these catalytic reactions, PdI μ-allyl dimer formation is a deleterious process which removes the IPr-Pd0 active species from the reaction mixture. However, increased sterics at the 1-position of the allyl ligand in the Pd(IPr)( η3-crotyl)Cl and Pd(IPr)( η3-cinnamyl)Cl precatalysts results in a larger kinetic barrier to comproportionation, which allows more of the active IPr-Pd0 catalyst to enter the catalytic cycle when these substituted precatalysts are used. Furthermore, we have developed reaction conditions for the Suzuki-Miyaura reaction using Pd(IPr)( η3-cinnamyl)Cl which are compatible with mild bases.

Synthesis and reactivity of alkylpalladium N-heterocyclic carbene complexes

The transamination of alkylpalladium halide N-heterocyclic carbene complexes has enabled the isolation of products that reveal interesting insights into the factors which might be barriers to the development of a palladium-catalysed alkyl-amination reaction. The Royal Society of Chemistry.

Alkylpalladium n-heterocyclic carbene complexes: Synthesis, reactivity, and catalytic properties

The dimers [trans-[(neopentyl)Pd(μ-Cl)(rBu)]2, 2, and (cis-[(neopentyl)Pd(μ-Cl)(IPr)]2,3 (ItBu = 1,3-bis-tert-butylimidazol-2-ylidene, IPr = l,3-bis-2,6-diidopropylimidazol-2- ylidene), have been synthesized from [Pd(neopentyl)(Cl)(l,5-COD)], and their reactivity toward a variety of nucleophiles has been evaluated. In particular, this study revealed that 2 can be readily cleaved by primary and secondary amines, affording stable transamination products, which are surprisingly resistant to deprotonation. Dimer 3 was subsequently used as a catalyst in a series of Buchwald-Hartwig animation reactions of aryl chlorides.

Palladium(0) NHC complexes: A new avenue to highly efficient phosphorescence

We report the first examples of highly luminescent di-coordinated Pd(0) complexes. Five complexes of the form [Pd(L)(L′)] were synthesized, where L = IPr, SIPr or IPr? NHC ligands and L′ = PCy3, or IPr and SIPr NHC ligands. The photophysical properties of these complexes were determined in degassed toluene solution and in the solid state and contrasted to the poorly luminescent reference complex [Pd(IPr)(PPh3)]. Organic light-emitting diodes were successfully fabricated but attained external quantum efficiencies of between 0.3 and 0.7%.

Facile oxidative addition of organic halides to heteroleptic and homoleptic Pd0-N-heterocyclic carbene complexes

Novel heteroleptic Pd0 complexes with an N-heterocyclic carbene (NHC) ligand [(Me3P)Pd(NHC)] (NHC = IPr, 1; SIPr, 2) were obtained from [Pd(CH2=CHPh)(PMe3)2] and an equivalent of NHC [NHC = 1,3-bis(2,

Synthesis, characterization, and reactivity of N-heterocyclic carbene palladium(II) hydroxide dimers

Palladium hydroxide dimers were prepared by reactions of CsOH with monomeric [Pd(NHC)(η3-allyl)Cl] starting materials. The dimers represent species proposed as intermediates in important cross-coupling reactions. These complexes were tested for their catalytic activity in Suzuki-Miyaura coupling and Buchwald-Hartwig aryl amination. The hydroxide complexes were susceptible to hydrogenolysis on exposure to H2 gas. Following H2O elimination and β-hydride elimination of an additional cinnamyl ligand, a Pd(0) species is formed which can react with other available ligands.

Palladium(I)-bridging allyl dimers for the catalytic functionalization of CO2

In general, the chemistry of both η1-allyl and η3-allyl Pd complexes is extremely well understood; η1-allyls are nucleophilic and react with electrophiles, whereas η3-allyls are electrophilic and react with nucleophiles. In contrast, relatively little is known about the chemistry of metal complexes with bridging allyl ligands. In this work, we describe a more efficient synthetic methodology for the preparation of PdI-bridging allyl dimers and report the first studies of their stoichiometric reactivity. Furthermore, we show that these compounds can activate CO2 and that an N-heterocyclic carbene-supported dimer is one of the most active and stable catalysts reported to date for the carboxylation of allylstannanes and allylboranes with CO 2.