PEPPSI‐Effect on Suzuki–Miyaura Reactions Using 4,5‐Dicyano‐1,3‐dimesitylimidazol‐2‐ylidene‐Palladium Complexes: A Comparison between trans‐Ligands

Abstract

The PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) complexes 12-15 with the structure [PdCl 2 {(CN) 2 IMes}(3-R-py)] (12: R = H; 13: R = Cl; 14: R = Br; 15: R = CN) bearing the maleonitrile-based N-heterocyclic carbene (NHC) (CN) 2 IMes ({(CN) 2 IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) were prepared. Solid state structures of 14 and 15 were obtained. Complexes 14 and 15 adopt a slightly distorted square-planar coordination geometry in the solid state with the substituted pyridine ligand trans to the NHC. Catalytic activities of precatalysts 12-15 were studied and subsequently compared to complexes

Suzuki–Miyaura and Hiyama coupling catalyzed by PEPPSI-type complexes with non-bulky NHC ligand

“…The presented catalysts have in our opinion advantages over the recently reported PEPPSI-type complexes which formed Pd(0) NPs operating according to the heterogeneous pathway [22].…”

“…There are many examples of the application of PEPPSI complexes in the Suzuki-Miyaura reaction, in which their excellent catalytic activity and versatility are clearly evidenced [18][19][20][21][22][23][24]. In contrast, their applications in the Hiyama coupling are rather scarce [25][26][27].…”

Pallada‐ and platinacycle complexes of phosphorus ylides; synthesis, X‐ray characterization, theoretical and electrochemical studies and application of Pd(II) complexes as catalyst in Suzuki‐Miyaura coupling reaction

“…Table shows a comparison between the efficiency of this catalytic system in Suzuki‐Miyaura coupling reaction of aryl chlorides and other catalytic systems. The results showed that the most active palladacycles, N‐heterocyclic carbenes (NHCs) and pyridine‐enhanced precatalyst preparation stabilization and initiation (PEPPSI)‐type Pd complexes need to be used in high loadings and showed lower activity with aryl chloride substrates . From an industrial view point, the low catalyst loading and short reaction time make this palladacycle as an ideal catalyst for the Suzuki‐Miyaura coupling reaction.…”

Poisonous Truth about the Mercury Drop Test: The Effect of Elemental Mercury on Pd(0) and Pd(II)ArX Intermediates

“…For example, the reactivity of mercury with palladium in N-heterocyclic carbene (NHC) and in C,N-and C,P-palladacycle ligand systems has raised concerns about the accuracy of the test. 27−29 While many have used the inhibition of catalysis upon the addition of mercury prior to catalyst activation as evidence for the involvement of heterogeneous species, 30,31 Gorunova and co-authors suggested that this could indicate reactivity with the homogeneous precatalyst. 28 Work by Chernychev and coauthors recently provided evidence for such interactions, demonstrating how the precatalyst tris(dibenzylideneacetone)dipalladium(0), Pd 2 (dba) 3 , reacted with Hg 0 to form free dba and other organomercuric species, leading to the nearcomplete disappearance of dissolved palladium within 30 min.…”