On the Use of Non‐Symmetrical Mixed PCN and SCN Pincer Palladacycles as Catalyst Precursors for the Heck Reaction

Abstract

OPPh 2 and t-BuSCH 2 CH 2 C ¼ C(o-NC 5 H 4 ), respectively. The molecular structures of 1 and 3 have been ascertained by means of X-ray diffraction analysis. The catalytic properties of these mixed donor group pincer-type palladacycles have been evaluated in the arylation of olefins (Heck reaction). The pincer palladacycle 1 is highly active for the coupling of aryl iodides and aryl bromides with n-butyl acrylate. In contrast it is only moderately active for the coupling of aryl chlorides substituted with electron-withdrawing groups and inactive for the coupling of electron neutral and electron deactivated aryl chlorides.

Suzuki reaction: mechanistic multiplicity versus exclusive homogeneous or exclusive heterogeneous catalysis

“…In Pd/C catalyzed Heck reactions under the same conditions ρ magnitudes were greater than 2 ( Figure 7) which correlated with the data of other investigators for the Heck reaction with aryl bromides. 51,54,55 The ρ parameters obtained in our work in different instances of the Suzuki competitive reaction for both PdCl 2 and Pd/C were less than 2 which was also consistent with the data of other researchers. 56,57 A single exception is the work 9 where the ρ magnitude for the Suzuki reaction was greater than 2 and practically concurred with the magnitude obtained for the Heck reaction .…”

Facile synthesis of achiral and chiral PCN pincer palladium(II) complexes and their application in the Suzuki and copper-free Sonogashira cross-coupling reactions

“…Taking these results into account, it seems very interesting to develop hybrid, non-symmetrical YCY 0 pincer Pd complexes such as PCN type since different donors (''hard" N and ''soft" P in PCN pincers) may provide a better tuning of the catalytic properties or give unique reactivity. By contrast, the synthesis and applications of non-symmetrical pincer Pd complexes have less often been reported [25][26][27][28][29][30]. This is partly because their preparation is a considerable challenge, which is laborious and requires a series of steps to introduce different donors.…”

A Simple and Efficient Copper‐Free Catalytic System Based on a Palladacycle for the Arylation of Alkynes

“…DCT inhibition tests. The use of s 0 constants results in good fits and correlations yielding a value close to 1 ¼ 1.0 independent of the base used, indicating that the electronic influence on the reaction rate is not so pronounced if compared with Heck or Suzuki coupling reactions where 1 values for iodoarenes can reach 1.8 -2.0 [50] that are close to the value of 2.0 observed for the oxidative addition reaction of iodoarenes with [Pd (PPh 3 ) 4 ]. [51,52] Therefore in case of aryl iodides the rate-determining step (which is sensitive to the electronic influence of aryl iodide) is most probably not the oxidative addition of the aryl halide to Pd(0) species for the alkynylation promoted by palladacycle 1.…”