Mechanisms for the Oxidative Addition of Palladium(0) Complexes to Arenediazonium Salts

Autor(es)

Esteves, Henrique ; da Silva, Vitor H. Menezes ; Correia, Carlos R. D. ; Braga, Ataualpa A. C.

• Tipo de documento: Artigo Científico
• Fonte: Organometallics; v. 42, n. 22, p. 14-pg., 2023-11-06.

Resumo

A detailed computational analysis was carried out using density functional theory (DFT) calculations to investigate the reaction between arenediazonium salts and Pd(0) complexes under "ligand-less" conditions. In the present study, three plausible mechanisms scenarios were revealed: nucleophilic substitution, intramolecular insertion, and a multistep 1,3-palladium migration. The oxidative addition of palladium to aryldiazonium cation (<bold>ArN</bold>(<bold>+</bold>)(<bold>2</bold>)) is a rapid and irreversible reaction. Additionally, <bold>ArN</bold>(<bold>+</bold>)(<bold>2</bold>) counterion BF4- does not have a significant impact on the reaction free energy profile. Based on the DFT calculations, the formation of the aryl-palladium(II) complex is identified as the thermodynamic driving force, regardless of the investigated reaction mechanism. The multistep 1,3-palladium migration mechanism is preferred, but the nucleophilic substitution and intramolecular insertion mechanisms could not be ruled out. According to the natural population analysis (NPA) of charges, the oxidation of Pd(0) takes place through the coordination of cation <bold>ArN</bold>(<bold>+</bold>)(<bold>2</bold>) to the metal specifically for the multistep 1,3-palladium migration mechanism, in contrast to the aryl halide counterpart systems, in which the oxidation of Pd(0) occurs in transition-state structures. The reaction thermodynamics is affected by the electronics of the para-substituents in the phenyl ring of <bold>ArN</bold>(<bold>+</bold>)(<bold>2</bold>). However, the overall reaction barriers are less affected by the electronics of substituents. Additionally, the computational investigation was carried out under different "ligand-less" conditions using methanol (MeOH), N,N-dimethylformamide (DMF), and acetonitrile (MeCN) as solvents. Specifically, for the MeCN solvent, the oxidative addition of Pd(0) to <bold>ArN</bold>(<bold>+</bold>)(<bold>2</bold>) was found to be less exothermic. Taken together, the strong electron acceptor capacity and high reactivity of <bold>ArN</bold>(<bold>+</bold>)(<bold>2</bold>) provide facile oxidation of Pd(0) and a strongly positively charged metal atom in all palladium-containing reaction intermediates and transition states, reflecting the low free energy barriers and high reaction exothermicity revealed by the calculations at room temperature. Furthermore, the current computational study suggests that the palladium(II) aryldiazenido complexes (<bold>int6a</bold> or <bold>int6b</bold>) are stable reaction intermediates, indicating them as promising precursor complexes for prospective experimental mechanistic investigations. (AU)

• Processo FAPESP: 14/25770-6 - Novas fronteiras em reações de acoplamento cruzado mediadas por paládio: associando catálise enantiosseletiva, ativações C-H, novos materiais e reações em fluxo visando alta eficiência e sustentabilidade em processos sintéticos
• Beneficiário: Carlos Roque Duarte Correia
• Modalidade de apoio: Auxílio à Pesquisa - Temático
• Processo FAPESP: 17/18207-1 - Avaliação de novos catalisadores quirais de paládio e aplicação no desenvolvimento da reação de Heck-Matsuda enantiosseletiva em novos modelos olefínicos: estudos computacionais
• Beneficiário: Vitor Hugo Menezes da Silva
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 13/07600-3 - CIBFar - Centro de Inovação em Biodiversidade e Fármacos
• Beneficiário: Glaucius Oliva
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs
• 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
• Processo FAPESP: 16/18061-4 - Arilação de Heck-Matsuda de Éteres Alquenílicos e Derivados: Expansão, Estudos Mecanísticos e Aplicações Sintéticas da Estratégia de Redox-Relay
• Beneficiário: Henrique Esteves
• Modalidade de apoio: Bolsas no Brasil - Doutorado