Co-ligand effects in the catalytic activity of Pd(II)–NHC complexes

Synthesis and Structure of a Trinuclear Pd–Ag–Pd Carbene Acetato Complex

“…However the obtained data sets were of poor quality and the authors abstained from a discussion of the bond lengths and angles. Huynh reported another trinuclear Pd–Ag–Pd carbene trifluoroacetato complex, which consists of two palladium biscarbene units, a silver ion, and trifluoroacetic acid anions with an unusual [Ag 2 (CF 3 COO – ) 3 (CH 3 C(O)CH 3 ) 2 ] counterion 19. The reported structure is quite similar to our structure, albeit symmetrical with the silver atom as a center of inversion.…”

Synthesis of palladium(0) and -(ii) complexes with chelating bis(N-heterocyclic carbene) ligands and their application in semihydrogenation

“…The bis-carbene bite angle of the complex is 87.50(9)°, a small deviation from the ideal angle dictated by the methylene bridge. 39 The palladium(0)-carbene bond distances of 3a are shorter than those of the recently reported Y-shaped [Pd 0 (bis-NHC)- 43 The CvC double bond of the maleic anhydride, which is η 2 coordinated to the metal center and almost perpendicular to the coordination plane (Fig. 2), is elongated compared to the free alkene due to π-back bonding from the palladium(0) center.…”

Chelating Bis(N‐Heterocyclic Carbene) Palladium‐Catalyzed Reactions

“…Huynh and co-workers investigated the effect of the coligando nc atalytic activity in the coupling between tertbutyl acrylate and aryl bromides (or chlorides). [11] Amongc om- plexes 2b-d,apositive coligand effect in the order of SCN < I < CF 3 COO was obtained, which demonstrated that the good carboxylato leaving group was beneficialt os ubstrate activation during the catalytic process. In contrast, halide and pseudo-halide groups were more difficult to cleave and resulted in inferioractivities.…”

“…Later, high activity of chiral complex 109 was observed by Veige and co‐workers in the reaction between 2‐cyclohexenone and phenylboronic acid, although only a moderate 50 % ee for the R enantiomer was reached . In a report by Huynh and co‐workers, the superior performance of achiral complex 2 d (Figure ) was also achieved in the conjugate addition between arylboronic acids and cyclic enones . This high catalytic efficacy was explained by the lability of the carboxylato coligand.…”

“…In comparison, complex 6 was more active at a high catalyst loading, whereas 7 , with TON of 7×10 5 , became better than that of 6 at a low catalyst loading 10 −4 mol %, owing to its low solubility in the Mizoroki–Heck reaction between styrene and 4‐bromoacetophenone in N , N ′‐dimethylacetamide (DMA). Huynh and co‐workers investigated the effect of the coligand on catalytic activity in the coupling between tert‐ butyl acrylate and aryl bromides (or chlorides) . Among complexes 2 b – d , a positive coligand effect in the order of SCN<I<CF 3 COO was obtained, which demonstrated that the good carboxylato leaving group was beneficial to substrate activation during the catalytic process.…”