N-Heterocyclic Carbene Based Nickel and Palladium Complexes: A DFT Comparison of the Mizoroki-Heck Catalytic Cycles

Autor(es)

Menezes da Siva, Vitor H. ; Braga, Ataualpa A. C. ; Cundari, Thomas R.

• Tipo de documento: Artigo Científico
• Fonte: Organometallics; v. 35, n. 18, p. 3170-3181, SEP 26 2016.
• Citações Web of Science: 14

Resumo

A theoretical investigation has been performed on nickel- and palladium-N-heterocyclic carbene (NHC) complexes in the Mizoroki-Heck (MH) reaction. A density functional theory (DFT) comparison of reaction pathways in cationic and neutral catalytic cycles for both metals was made using the M06 functional. The oxidative addition barrier is much lower for NHC-Ni than that for NHC-Pd for both mono- and bis-ligand pathways; the bis-ligand pathway (i.e., where both NHCs remain coordinated) is energetically more favorable for both metals. The migratory insertion steps have lower free energy barriers for NHC-Ni than for NHC-Pd complexes for both neutral and cationic pathways. beta-Hydride elimination is computed as thermodynamically difficult for NHC-Ni complexes, indicating a possible reluctance in the elimination of the Ni-based hydride intermediate and formation of the Heck adduct at room temperature. The base-assisted reductive elimination is easier for NHC-Pd than for NHC-Ni complexes in the neutral and cationic pathways, in agreement with reported experimental observations. (AU)

• Processo FAPESP: 13/04813-6 - Estudos mecanísticos da reação de Heck-Matsuda: uma investigação teórica
• Beneficiário: Vitor Hugo Menezes da Silva
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 15/11840-5 - Estudo teórico sobre a seletividade das reações de Heck-Mizoroki: uma comparação mecanística entre catalisadores de Ni e Pd
• Beneficiário: Vitor Hugo Menezes da Silva
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 15/01491-3 - Estudo teórico das reações de acoplamento-cruzado: catálise homogênea e heterogênea
• Beneficiário: Ataualpa Albert Carmo Braga
• Modalidade de apoio: Auxílio à Pesquisa - Regular