Pd(II) complexes with mono- and bis-chelate carbene ligands tagged with pyridinium cation: Synthesis, structures, and their catalytic activities toward Heck reaction

Highly Recoverable Pd(II) Catalysts for the Mizoroki–Heck Reaction Based on N-Heterocyclic Carbenes and Poly(benzyl ether) Dendrons

“…Moreover, the induction periods are shorter in the reloading cycles, as can be clearly observed for 9 in Figure . As previously observed for similar catalysts, the addition of an ammonium halide produces a comparable effect on the induction periods and the reloading cycles are initiated in the presence of the [NEt 3 H]I formed during the initial cycle of the MH reaction. After the induction period, the catalytic rates are slightly dependent on the type of cycle and tend to increase in the following order: initial cycle performed without catalyst preincubation < reloading cycles < initial cycle with preincubation.…”

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

“…The authors also prepared monopalladium complex 52 by adding one equivalent of [PdCl 2 (CH 3 CN) 2 ]i nC H 3 CN to the transmetalation reaction, whereas m-chloro-coordinated dipalladium complex 53 was obtained by using two equivalents of [PdCl 2 (CH 3 CN) 2 ]i nD MSO. [37] Complex 53 outperformed complex 52 in the Mizoroki-Heck reactioni nb oth ab asic solution in DMF (NaOAc) and aqueous medium in the presence of Cs 2 CO 3 .T he integrity of 52 was preserveda fter the reaction, whereas 53 convertedi nto am onopalladium species. Thus, the superior recyclability of complex 52 was also indicated by recycling tests.…”

“…It was proposed that the Pd 0 –NHC complex was the active species during the catalytic cycle based on a cyclic voltammetry test through which a quasi‐reversible palladium(II)/palladium(0) couple was confirmed. The authors also prepared monopalladium complex 52 by adding one equivalent of [PdCl 2 (CH 3 CN) 2 ] in CH 3 CN to the transmetalation reaction, whereas μ‐chloro‐coordinated dipalladium complex 53 was obtained by using two equivalents of [PdCl 2 (CH 3 CN) 2 ] in DMSO . Complex 53 outperformed complex 52 in the Mizoroki–Heck reaction in both a basic solution in DMF (NaOAc) and aqueous medium in the presence of Cs 2 CO 3 .…”

“…This induction period could also be facilitated by adding nBu 4 NBr.T he Pd 0 -NHC intermediate was also expected to be the catalytic species upon employing precatalyst 52.T he pyridinium auxiliary accounted for the highera ctivity of complex 52 in comparison with its counterpart 51,which hadn opyridinium group. [36,37]…”

1,3-Bis[(5-aminofuran-2-yl)methyl]-3,4,5,6-tetrahydropyrimidin-1-ium hexafluorophosphate

“…In recent years, NHCs are fully used as organocatalysts and ancillary ligands in transition metal catalyzed reactions (Hermann, 2002). They have attracted many attention, particularly for its functions in catalytic reactions (Akkoç & Gök, 2013;Lee et al, 2013;Bagherzadeh et al, 2012;Çetinkaya et al, 1997;Özdemir et al, 2001;Saba et al, 1991;Yiğit et al, 2007). Fig.…”