Desidrogenação do ácido fórmico catalisada por complexos bidentados N-heterocíclicos de carbeno/areno-rutênio(II)
Palavras-chave:
Desidrogenação, Ácido Fórmico, Liquido Iônico, Rutênio, NHC.Resumo
Os complexos de rutênio Ru-BzPyPh, Ru-BzPyTol e Ru-BzPyMeO foram sintetizados com rendimentos de 80-85% pela reação entre [Ru(p-cimeno)Cl₂]₂ e ligantes NHC, utilizando óxido de prata como agente de transmetalação. A caracterização foi realizada por RMN, FT-IR, UV-Vis, ESI-HRMS e. Os complexos Ru-BzPyL apresentaram alta solubilidade em ácido fórmico (FA) e eficiência na desidrogenação, com TOF máximo de 1366 h⁻¹ usando 75% de NEt₃ como aditivo para o Ru-BzPyPh. Aumentos na concentração além de 75% reduziram o TOF para 1100 h⁻¹ devido à formação de fases bifásicas. O BMIm.OAc foi o aditivo mais eficiente, alcançando 95% de conversão e TOF de 1455 h⁻¹. Complexos com ligantes BzPyTol mostraram atividades similares ao Ru-BzPyPh, enquanto o BzPyMeO apresentou menor desempenho, com TOF de 681 h⁻¹. A análise térmica indicou que temperaturas acima de 85 °C são essenciais para uma catálise eficiente, permitindo a determinação de ΔS‡ = -12,52 e.u. e Ea = 68,36 kJ mol⁻¹. O sistema Ru-BzPyPh/BMIm.OAc mostrou alta estabilidade, mantendo o desempenho catalítico por 20 dias, com TON máximo de 956 por ciclo.
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